Transparent conducting F-doped texture SnO2 films with resistivity as low as 5× 10-4 Ω ·cm,with carrier concentrations between 3.5 × 1020 and 7× 1020 cm-3 and Hall mobilities from 15.7 to 20.1 cm2...Transparent conducting F-doped texture SnO2 films with resistivity as low as 5× 10-4 Ω ·cm,with carrier concentrations between 3.5 × 1020 and 7× 1020 cm-3 and Hall mobilities from 15.7 to 20.1 cm2/(V/s) have been prepared by atmosphere pressure chemical vapour deposition (APCVD). These polycrystalline films possess a variable preferred orientation, the polycrystallite sizes and orientations vary with substrate temperature. The substrate temperature and fluorine flow rate dependence of conductivity, Hall mobility and carrier conentration fOr the resultingfilms have been obtained. The temperature dependence of the mobiity and carrier concentrationhave been measured over a temperature range 16～400 K. A systematically theoretical analysis on scattering mechanisms for the highly conductive SnO2 films has been given. Both theoretical analysis and experimental results indicate that for these degenerate, polycrystalline SnO2 ：F films in the low temperature range (below 100 K), ionized impurity scattering is main scattering mechanism. However, when the temperature is higher than 100 K, the lattice vibration scattering becomes dominant. The grain boundary scattering makes a small contribution to limit the mobility of the films.展开更多
To attain the objectives of carbon peaking and carbon neutrality,the development of stable and highperformance ion-conducting materials holds enormous relevance in various energy storage and conversion devices.Particu...To attain the objectives of carbon peaking and carbon neutrality,the development of stable and highperformance ion-conducting materials holds enormous relevance in various energy storage and conversion devices.Particularly,crystalline porous materials possessing built-in ordered nanochannels exhibit remarkable superiority in comprehending the ion transfer mechanisms with precision.In this regard,covalent organic frameworks(COFs)are highly regarded as a promising alternative due to their preeminent structural tunability,accessible well-defined pores,and excellent thermal/chemical stability under hydrous/anhydrous conditions.By the availability of organic units and the diversity of topologies and connections,advances in COFs have been increasing rapidly over the last decade and they have emerged as a new field of proton-conducting materials.Therefore,a comprehensive summary and discussion are urgently needed to provide an"at a glance"understanding of the prospects and challenges in the development of proton-conducting COFs.In this review,we target a comprehensive review of COFs in the field of proton conductivity from the aspects of design strategies,the proton conducting mechanism/features,the relationships of structure-function,and the application of research.The relevant content of theoretical simulation,advanced structural characterizations,prospects,and challenges are also presented elaborately and critically.More importantly,we sincerely hope that this progress report will form a consistent view of this field and provide inspiration for future research.展开更多
Rapid development of energy,electrical and electronic technologies has put forward higher requirements for the thermal conductivities of polymers and their composites.However,the thermal conductivity coefficient(λ)va...Rapid development of energy,electrical and electronic technologies has put forward higher requirements for the thermal conductivities of polymers and their composites.However,the thermal conductivity coefficient(λ)values of prepared thermally conductive polymer composites are still difficult to achieve expectations,which has become the bottleneck in the fields of thermally conductive polymer composites.Aimed at that,based on the accumulation of the previous research works by related researchers and our research group,this paper proposes three possible directions for breaking through the bottlenecks:(1)preparing and synthesizing intrinsically thermally conductive polymers,(2)reducing the interfacial thermal resistance in thermally conductive polymer composites,and(3)establishing suitable thermal conduction models and studying inner thermal conduction mechanism to guide experimental optimization.Also,the future development trends of the three above-mentioned directions are foreseen,hoping to provide certain basis and guidance for the preparation,researches and development of thermally conductive polymers and their composites.展开更多
Dc/ac transport characteristic of PECVD grown hydrogenated amorphous silicon carbide (a-SiCx:H) thin film was investigated in MIS (metal/insulator/semiconductor) structure by dc current/voltage (I/V) at different temp...Dc/ac transport characteristic of PECVD grown hydrogenated amorphous silicon carbide (a-SiCx:H) thin film was investigated in MIS (metal/insulator/semiconductor) structure by dc current/voltage (I/V) at different temperature (T), ac admittance vs. temperature at constant gate bias voltages and deep level transient spectroscopy (DLTS), respectively. According to I-V-T analysis, two main regimes exhibited. At low electric field, apparent Ohm’s law dominated with Arrhenius type thermal activation energy (EA) around 0.4 eV in both forward and reverse directions. At high field, on the contrary, space charge limited (SCL) current mechanism was eventual. The current transport mechanisms and its temperature/frequency dependence were interpreted by a thermally activated hopping processes across the localized states within a-SiCx:H thin film since 0.4 eV as EA was not high enough for intrinsic band conduction. Instead, transport of charge carriers took place in two steps;first a carrier is thermally excited to an empty energy level from an occupied state then multi-step tunnelling or hopping starts over. Therefore, the two steps mechanisms manifested as single activation energy, differing only through capture cross sections. In turn, two steps in capacitance together with conductance peaks in C-(G)-T while convoluted DLTS signal associated with such events in the measurements.展开更多
Metal-organic frameworks(MOFs),typically constructed with metallic nodes and organic linkers,have influenced the development of modular solid materials.Their adjustable molecular structure provides a remarkable variet...Metal-organic frameworks(MOFs),typically constructed with metallic nodes and organic linkers,have influenced the development of modular solid materials.Their adjustable molecular structure provides a remarkable variety of MOF-based solid-state structures towards diverse applications.However,the low conductivity of traditional MOFs extremely hinders their applications in electronic and electrochemical devices.The emerging conductive MOFs,generally possessing twodimensional layered structures,are endowed with both the structural merits of common MOFs and exceptional electronic/ionic conductivities.Besides,the selection and optimization of ligands and metal centers,as well as synthetic methods enormously affects the intrinsic conductivity of conductive MOFs.The distinctive crystal structures and superb conductivity promise their appealing applications in electrochemical energy-related fields.In the review,we mainly summarize representative crystal features,conducting mechanisms and recent advances in rational design and synthesis of conductive MOFs,along with their versatile applications as electrodes for electrochemical capacitors and rechargeable batteries,and as catalysts towards electrocatalysis.Finally,the involved challenges and future trends/prospects of the conductive MOFs for electrochemical energyrelated applications are further proposed.展开更多
Chromite,a crucial high-conductivity mineral phase of peridotite in ophiolite suites,has a significant effect on the electrical structure of subduction zones.The electrical conductivities of sintered polycrystalline o...Chromite,a crucial high-conductivity mineral phase of peridotite in ophiolite suites,has a significant effect on the electrical structure of subduction zones.The electrical conductivities of sintered polycrystalline olivine containing various volume percents of chromite(0,4,7,10,13,16,18,21,23,100 vol.%)were measured using a complex impedance spectroscopic technique in the frequency range of 10^(−1)-10^(6) Hz under the conditions of 1.0-3.0 GPa and 873-1223 K.The relationship between the conductivities of the chromite-bearing olivine aggregates and temperatures conformed to the Arrhenius equation.The positive effect of pressure on the conductivities of the olivine-chromite systems was much weaker than that of temperature.The chromite content had an important effect on the conductivities of the olivine-chromite systems,and the bulk conductivities increased with increasing volume fraction of chromite to a certain extent.The inclusion of 16 vol.%chromites dramatically enhanced the bulk conductivity,implying that the percolation threshold of interconnectivity of chromite in the olivine-chromite systems is-16 vol.%.The fitted activation enthalpies for pure polycrystalline olivine,polycrystalline olivine with isolated chromite,polycrystalline olivine with interconnected chromites,and pure polycrystalline chromite were 1.25,0.78-0.87,0.48-0.54,and 0.47 eV,respectively.Based on the chemical compositions and activation enthalpies,small polaron conduction was proposed to be the dominant conduction mechanism for polycrystalline olivine with various chromite contents.Furthermore,the conductivities of polycrystalline olivine with interconnected chromite(10-1.5-100.5 S/m)provides a reasonable explanation for the high conductivity anomalies in subduction-related tectonic environments.展开更多
High thermal conductivity dense silica bricks have the higher thermal conductivity than ordinary silica bricks,which is conducive to the realization of energy saving and emission reduction in the iron and steel indust...High thermal conductivity dense silica bricks have the higher thermal conductivity than ordinary silica bricks,which is conducive to the realization of energy saving and emission reduction in the iron and steel industry.The performance of ordinary silica bricks and high thermal conductivity dense silica bricks was compared,and the high thermal conductivity mechanism was analyzed.The results show that(1)compared with ordinary silica bricks,high thermal conductivity dense silica bricks have the characteristics of higher thermal conductivity,lower apparent porosity,higher tridymite content,higher compressive strength,and higher thermal expansion;(2)by increasing the tridymite content and reducing the porosity,the close packing of honeycombα-tridymite improves the density and continuity of the SiO_(2)frame structure of the silica bricks,and the larger area perpendicular to the heat transfer direction improves the thermal conductivity of the bricks;(3)the densification of the silica bricks also increases the thermal expansion of the bricks,but they still meet the standard requirements.展开更多
BiFeO_(3)–BaTiO_(3)(BF–BT)based piezoelectric ceramics are a kind of high-temperature lead-free piezoelectric ceramics with great development prospects due to their high Curie temperature(TC)and excellent electrical...BiFeO_(3)–BaTiO_(3)(BF–BT)based piezoelectric ceramics are a kind of high-temperature lead-free piezoelectric ceramics with great development prospects due to their high Curie temperature(TC)and excellent electrical properties.However,large leakage current limits their performance improvement and practical applications.In this work,direct current(DC)test,alternating current(AC)impedance,and Hall tests were used to investigate conduction mechanisms of 0.75BiFeO_(3)–0.25BaTiO_(3)ceramics over a wide temperature range.In the range of room temperature(RT)−150℃,ohmic conduction plays a predominant effect,and the main carriers are p-type holes with the activation energy(Ea)of 0.51 eV.When T>200℃,the Ea value calculated from the AC impedance and Hall data is 1.03 eV with oxygen vacancies as a cause of high conductivity.The diffusion behavior of thermally activated oxygen vacancies is affected by crystal symmetry,oxygen vacancy concentration,and distribution,dominating internal conduction mechanism.Deciphering the conduction mechanisms over the three temperature ranges would pave the way for further improving the insulation and electrical properties of BiFeO_(3)–BaTiO_(3)ceramics.展开更多
Construction of proton transport channels in metal-organic frameworks(MOFs)with simple synthesis processes,high proton conductivities and good performance stabilities has been of great interest for proton exchange mem...Construction of proton transport channels in metal-organic frameworks(MOFs)with simple synthesis processes,high proton conductivities and good performance stabilities has been of great interest for proton exchange membrane fuel cell(PEMFC).Herein,we mimic the proton transport behavior of amino acid residues in bacteriorhodopsin,select UiO-66-COOH as the host,glycine and aspartic acid as the functional guest molecules,and then functionalize the MOF framework with amino acids to obtain biomimetic proton transport channels.This strategy endows UiO-66-COOH-Asp a high proton conductivity of 1.19×10^(-2)S/cm at 70℃and 98%RH,excellent cycle stability of performances and performance durability,which can be comparable to the reported MOFs-based proton conductors.Moreover,the proton conduction mechanism in UiO-66-COOH-Asp is elaborated in detail due to its visual structure,which is also one of the advantages of adopting MOFs as research platform,making it possible to optimize the structure-activity relationship of advanced materials.Notably,this strategy has clear objectives and simple synthesis,which has made certain contributions to both theoretical research and future industrial production of proton conductors.展开更多
Electrical characterization analyses are proposed in this work using the Lambert function on Schottky junctions in GaN wide band gap semiconductor devices for extraction of physical parameters.The Lambert function is ...Electrical characterization analyses are proposed in this work using the Lambert function on Schottky junctions in GaN wide band gap semiconductor devices for extraction of physical parameters.The Lambert function is used to give an explicit expression of the current in the Schottky junction.This function is applied with defined conduction phenomena,whereas other work presented arbitrary(or undefined)conduction mechanisms in such parameters' extractions.Based upon AlGaN/GaN HEMT structures,extractions of parameters are undergone in order to provide physical characteristics.This work highlights a new expression of current with defined conduction phenomena in order to quantify the physical properties of Schottky contacts in AlGaN/GaN HEMT transistors.展开更多
High entropy oxides(HEO)are single-phase solid solutions which are formed by the incorporation of five or more elements into a cationic sublattice in equal or near-equal atomic proportions.Its unique structural featur...High entropy oxides(HEO)are single-phase solid solutions which are formed by the incorporation of five or more elements into a cationic sublattice in equal or near-equal atomic proportions.Its unique structural features and the possibility of targeted access to certain functions have attracted great interest from researchers.In this review,we summarize the recent advances in the electronic field of high-entropy oxides.We emphasize the following three fundamental aspects of high-entropy oxides:(1)The conductivity mechanism of metal oxides;(2)the factors affecting the formation of single-phase oxides;and(3)the electrical properties and applications of high-entropy oxides.The purpose of this review is to provide new directions for designing and tailoring the functional properties of relevant electronic materials via a comprehensive overview of the literature on the field of high-entropy oxide electrical properties.展开更多
Almost unlimited reserves and low cost of sodium are accelerating the commercialization of sodiumion batteries.However,serious safety and stability issues,arising mainly from organic liquid electrolytes,hinder further...Almost unlimited reserves and low cost of sodium are accelerating the commercialization of sodiumion batteries.However,serious safety and stability issues,arising mainly from organic liquid electrolytes,hinder further developments of sodium-ion batteries.Polymer electrolytes might be a solution to the safety and stability issues due to the better safety of polymers.Herein,an overview is provided on recent advances in polymer electrolytes for solid-state sodium batteries,including solid polymer electrolytes,composite polymer electrolytes and gel polymer electrolytes.Fundamental properties,ionic conduction mechanisms and promising applications of polymer electrolytes are discussed,and pending challenges and effective solutions are emphasized.Hopefully,this review will promote commercial applications of polymer electrolytes in energy storage systems.展开更多
The intrinsic conduction mechanism and optimal sintering atmosphere of(Ba_(0.85)Ca_(0.15))(Zr_(0.1)Ti_(0.9))O_(3)(BCZT)ceramics were regulated by Mn-doping element in this work.By Hall and impedance analysis,the undop...The intrinsic conduction mechanism and optimal sintering atmosphere of(Ba_(0.85)Ca_(0.15))(Zr_(0.1)Ti_(0.9))O_(3)(BCZT)ceramics were regulated by Mn-doping element in this work.By Hall and impedance analysis,the undoped BCZT ceramics exhibit a typical n-type conduction mechanism,and the electron concentration decreases with the increasing oxygen partial pressure.Therefore,the undoped ceramics exhibit best electrical properties(piezoelectrical constant<733=585 pC·N^(-1),electro-mechanical coupling factor k_(p)=56%)in O_(2).A handful of Mn-doping element would transfer the conduction mechanism from n-type into p-type.And the hole concentration reduces with the decreasing oxygen partial pressure for Mn-doped BCZT ceramics.Therefore,the Mn-doped ceramics sintered in N_(2)have the highest insulation resistance and best piezoelectric properties(d_(33)=505 pC·N^(-1),k_(p)=50%).The experimental results demonstrate that the Mn-doping element can effectively adjust the intrinsic conduction mechanism and then predict the optimal atmosphere.展开更多
Ceramics of the composition BaBiO_(3)(BB)were sintered in oxygen to obtain a single phase with monoclinic I2/m symmetry as suggested by high-resolution X-ray diffraction.X-ray photoelectron spectroscopy confirmed the ...Ceramics of the composition BaBiO_(3)(BB)were sintered in oxygen to obtain a single phase with monoclinic I2/m symmetry as suggested by high-resolution X-ray diffraction.X-ray photoelectron spectroscopy confirmed the presence of bismuth in two valence states—3þand 5þ.Optical spectroscopy showed presence of a direct bandgap at-2.2 eV and a possible indirect bandgap at-0.9 eV.This combined with determination of the activation energy for conduction of 0.25 eV,as obtained from ac impedance spectroscopy,suggested that a polaron-mediated conduction mechanism was prevalent in BB.The BB ceramics were crushed,mixed with BaTiO_(3)(BT),and sintered to obtain BT–BB solid solutions.All the ceramics had tetragonal symmetry and exhibited a normal ferroelectric-like dielectric response.Using ac impedance and optical spectroscopy,it was shown that resistivity values of BT–BB were orders of magnitude higher than BT or BB alone,indicating a change in the fundamental defect equilibrium conditions.A shift in the site occupancy of Bi to the A-site is proposed to be the mechanism for the increased electrical resistivity.展开更多
Bis-Tetrapropylammonium tetrabromozincate was synthesized and characterized by X-ray powder diffraction,as well as vibrational and impedance spectroscopy.Rietveld’s refinement of X-ray diffractogram confirmed the cry...Bis-Tetrapropylammonium tetrabromozincate was synthesized and characterized by X-ray powder diffraction,as well as vibrational and impedance spectroscopy.Rietveld’s refinement of X-ray diffractogram confirmed the crystallization of the compound through the monoclinic system(space group C_(2/c)).A temperature study of Raman scattering revealed two phase transitions at approximately T_(1)=340 K and T_(2)=393 K.The wavenumber and the line width’s evolution as a function of temperature showed some peculiarities associated with these transitions,which suggests that they are governed by the reorientation of the organic part[N(C_(3)H_(7))_(4)]+.The complex impedance plotted as a double semicircular arc in the studied temperature range and the centers of these semicircles lie below the real axis,which indicates that the material is an on-Debye type.These semicircular arcs are related to the bulk and the grain boundary effects.Furthermore,the alternating current conductivity of[N(C_(3)H_(7))_(4)]_(2)ZnBr_(4)obeyed Jonscher’s law:σ_(AC)(ω)=σ_(dc)+Aω^(s) and the conduction could be attributed to the correlated barrier hopping(CBH)model in both region(I)and(II)and the Non-overlapping Small Polaron Tunneling(NSPT)in region(III).展开更多
文摘Transparent conducting F-doped texture SnO2 films with resistivity as low as 5× 10-4 Ω ·cm,with carrier concentrations between 3.5 × 1020 and 7× 1020 cm-3 and Hall mobilities from 15.7 to 20.1 cm2/(V/s) have been prepared by atmosphere pressure chemical vapour deposition (APCVD). These polycrystalline films possess a variable preferred orientation, the polycrystallite sizes and orientations vary with substrate temperature. The substrate temperature and fluorine flow rate dependence of conductivity, Hall mobility and carrier conentration fOr the resultingfilms have been obtained. The temperature dependence of the mobiity and carrier concentrationhave been measured over a temperature range 16～400 K. A systematically theoretical analysis on scattering mechanisms for the highly conductive SnO2 films has been given. Both theoretical analysis and experimental results indicate that for these degenerate, polycrystalline SnO2 ：F films in the low temperature range (below 100 K), ionized impurity scattering is main scattering mechanism. However, when the temperature is higher than 100 K, the lattice vibration scattering becomes dominant. The grain boundary scattering makes a small contribution to limit the mobility of the films.
基金financial support from the National Natural Science Foundation of China(21978024)the Beijing Natural Science Foundation(2202034)。
文摘To attain the objectives of carbon peaking and carbon neutrality,the development of stable and highperformance ion-conducting materials holds enormous relevance in various energy storage and conversion devices.Particularly,crystalline porous materials possessing built-in ordered nanochannels exhibit remarkable superiority in comprehending the ion transfer mechanisms with precision.In this regard,covalent organic frameworks(COFs)are highly regarded as a promising alternative due to their preeminent structural tunability,accessible well-defined pores,and excellent thermal/chemical stability under hydrous/anhydrous conditions.By the availability of organic units and the diversity of topologies and connections,advances in COFs have been increasing rapidly over the last decade and they have emerged as a new field of proton-conducting materials.Therefore,a comprehensive summary and discussion are urgently needed to provide an"at a glance"understanding of the prospects and challenges in the development of proton-conducting COFs.In this review,we target a comprehensive review of COFs in the field of proton conductivity from the aspects of design strategies,the proton conducting mechanism/features,the relationships of structure-function,and the application of research.The relevant content of theoretical simulation,advanced structural characterizations,prospects,and challenges are also presented elaborately and critically.More importantly,we sincerely hope that this progress report will form a consistent view of this field and provide inspiration for future research.
基金National Natural Science Foundation of China(51773169 and 51973173)Guangdong Basic and Applied Basic Research Foundation(2019B1515120093)+2 种基金Technological Base Scientific Research ProjectsNatural Science Basic Research Plan for Distinguished Young Scholars in Shaanxi Province(2019JC-11)Polymer Electromagnetic Functional Materials Innovation Team of Shaanxi Sanqin Scholars.
文摘Rapid development of energy,electrical and electronic technologies has put forward higher requirements for the thermal conductivities of polymers and their composites.However,the thermal conductivity coefficient(λ)values of prepared thermally conductive polymer composites are still difficult to achieve expectations,which has become the bottleneck in the fields of thermally conductive polymer composites.Aimed at that,based on the accumulation of the previous research works by related researchers and our research group,this paper proposes three possible directions for breaking through the bottlenecks:(1)preparing and synthesizing intrinsically thermally conductive polymers,(2)reducing the interfacial thermal resistance in thermally conductive polymer composites,and(3)establishing suitable thermal conduction models and studying inner thermal conduction mechanism to guide experimental optimization.Also,the future development trends of the three above-mentioned directions are foreseen,hoping to provide certain basis and guidance for the preparation,researches and development of thermally conductive polymers and their composites.
文摘Dc/ac transport characteristic of PECVD grown hydrogenated amorphous silicon carbide (a-SiCx:H) thin film was investigated in MIS (metal/insulator/semiconductor) structure by dc current/voltage (I/V) at different temperature (T), ac admittance vs. temperature at constant gate bias voltages and deep level transient spectroscopy (DLTS), respectively. According to I-V-T analysis, two main regimes exhibited. At low electric field, apparent Ohm’s law dominated with Arrhenius type thermal activation energy (EA) around 0.4 eV in both forward and reverse directions. At high field, on the contrary, space charge limited (SCL) current mechanism was eventual. The current transport mechanisms and its temperature/frequency dependence were interpreted by a thermally activated hopping processes across the localized states within a-SiCx:H thin film since 0.4 eV as EA was not high enough for intrinsic band conduction. Instead, transport of charge carriers took place in two steps;first a carrier is thermally excited to an empty energy level from an occupied state then multi-step tunnelling or hopping starts over. Therefore, the two steps mechanisms manifested as single activation energy, differing only through capture cross sections. In turn, two steps in capacitance together with conductance peaks in C-(G)-T while convoluted DLTS signal associated with such events in the measurements.
基金The authors acknowledge the financial support from National Natural Science Foundation of China(No.51772127,51772131,and 51802119)Taishan Scholars(No.ts201712050)+2 种基金Major Program of Shandong Province Natural Science Foundation(ZR2018ZB0317)Natural Science Doctoral Foundation of Shandong Province(ZR2018BEM018,ZR2019BB057)Collaborative Innovation Center of Technology and Equipment for Biological Diagnosis and Therapy in Universities of Shandong.
文摘Metal-organic frameworks(MOFs),typically constructed with metallic nodes and organic linkers,have influenced the development of modular solid materials.Their adjustable molecular structure provides a remarkable variety of MOF-based solid-state structures towards diverse applications.However,the low conductivity of traditional MOFs extremely hinders their applications in electronic and electrochemical devices.The emerging conductive MOFs,generally possessing twodimensional layered structures,are endowed with both the structural merits of common MOFs and exceptional electronic/ionic conductivities.Besides,the selection and optimization of ligands and metal centers,as well as synthetic methods enormously affects the intrinsic conductivity of conductive MOFs.The distinctive crystal structures and superb conductivity promise their appealing applications in electrochemical energy-related fields.In the review,we mainly summarize representative crystal features,conducting mechanisms and recent advances in rational design and synthesis of conductive MOFs,along with their versatile applications as electrodes for electrochemical capacitors and rechargeable batteries,and as catalysts towards electrocatalysis.Finally,the involved challenges and future trends/prospects of the conductive MOFs for electrochemical energyrelated applications are further proposed.
基金supported by NSF of China(Grant Nos.42072055,41774099 and 41772042)Youth Innovation Promotion Association of CAS(Grant No.2019390)Special Fund of the West Light Foundation of CAS and well as Special Fund from Shandong Provincial Key Laboratory of Water and Soil Conservation and Environmental Protection.
文摘Chromite,a crucial high-conductivity mineral phase of peridotite in ophiolite suites,has a significant effect on the electrical structure of subduction zones.The electrical conductivities of sintered polycrystalline olivine containing various volume percents of chromite(0,4,7,10,13,16,18,21,23,100 vol.%)were measured using a complex impedance spectroscopic technique in the frequency range of 10^(−1)-10^(6) Hz under the conditions of 1.0-3.0 GPa and 873-1223 K.The relationship between the conductivities of the chromite-bearing olivine aggregates and temperatures conformed to the Arrhenius equation.The positive effect of pressure on the conductivities of the olivine-chromite systems was much weaker than that of temperature.The chromite content had an important effect on the conductivities of the olivine-chromite systems,and the bulk conductivities increased with increasing volume fraction of chromite to a certain extent.The inclusion of 16 vol.%chromites dramatically enhanced the bulk conductivity,implying that the percolation threshold of interconnectivity of chromite in the olivine-chromite systems is-16 vol.%.The fitted activation enthalpies for pure polycrystalline olivine,polycrystalline olivine with isolated chromite,polycrystalline olivine with interconnected chromites,and pure polycrystalline chromite were 1.25,0.78-0.87,0.48-0.54,and 0.47 eV,respectively.Based on the chemical compositions and activation enthalpies,small polaron conduction was proposed to be the dominant conduction mechanism for polycrystalline olivine with various chromite contents.Furthermore,the conductivities of polycrystalline olivine with interconnected chromite(10-1.5-100.5 S/m)provides a reasonable explanation for the high conductivity anomalies in subduction-related tectonic environments.
文摘High thermal conductivity dense silica bricks have the higher thermal conductivity than ordinary silica bricks,which is conducive to the realization of energy saving and emission reduction in the iron and steel industry.The performance of ordinary silica bricks and high thermal conductivity dense silica bricks was compared,and the high thermal conductivity mechanism was analyzed.The results show that(1)compared with ordinary silica bricks,high thermal conductivity dense silica bricks have the characteristics of higher thermal conductivity,lower apparent porosity,higher tridymite content,higher compressive strength,and higher thermal expansion;(2)by increasing the tridymite content and reducing the porosity,the close packing of honeycombα-tridymite improves the density and continuity of the SiO_(2)frame structure of the silica bricks,and the larger area perpendicular to the heat transfer direction improves the thermal conductivity of the bricks;(3)the densification of the silica bricks also increases the thermal expansion of the bricks,but they still meet the standard requirements.
基金supported by the National Natural Science Foundation of China(Nos.52072028,52032007)National Key R&D Program of China(No.2022YFB3807400).
文摘BiFeO_(3)–BaTiO_(3)(BF–BT)based piezoelectric ceramics are a kind of high-temperature lead-free piezoelectric ceramics with great development prospects due to their high Curie temperature(TC)and excellent electrical properties.However,large leakage current limits their performance improvement and practical applications.In this work,direct current(DC)test,alternating current(AC)impedance,and Hall tests were used to investigate conduction mechanisms of 0.75BiFeO_(3)–0.25BaTiO_(3)ceramics over a wide temperature range.In the range of room temperature(RT)−150℃,ohmic conduction plays a predominant effect,and the main carriers are p-type holes with the activation energy(Ea)of 0.51 eV.When T>200℃,the Ea value calculated from the AC impedance and Hall data is 1.03 eV with oxygen vacancies as a cause of high conductivity.The diffusion behavior of thermally activated oxygen vacancies is affected by crystal symmetry,oxygen vacancy concentration,and distribution,dominating internal conduction mechanism.Deciphering the conduction mechanisms over the three temperature ranges would pave the way for further improving the insulation and electrical properties of BiFeO_(3)–BaTiO_(3)ceramics.
基金supported by the Zhejiang Provincial Natural Science Foundation of China(No.LY20E020001)Research Initiation Fund Project from Zhejiang Sci-Tech University(No.22212154-Y)the Fundamental Research Funds of Zhejiang Sci-Tech University(No.22212290-Y)。
文摘Construction of proton transport channels in metal-organic frameworks(MOFs)with simple synthesis processes,high proton conductivities and good performance stabilities has been of great interest for proton exchange membrane fuel cell(PEMFC).Herein,we mimic the proton transport behavior of amino acid residues in bacteriorhodopsin,select UiO-66-COOH as the host,glycine and aspartic acid as the functional guest molecules,and then functionalize the MOF framework with amino acids to obtain biomimetic proton transport channels.This strategy endows UiO-66-COOH-Asp a high proton conductivity of 1.19×10^(-2)S/cm at 70℃and 98%RH,excellent cycle stability of performances and performance durability,which can be comparable to the reported MOFs-based proton conductors.Moreover,the proton conduction mechanism in UiO-66-COOH-Asp is elaborated in detail due to its visual structure,which is also one of the advantages of adopting MOFs as research platform,making it possible to optimize the structure-activity relationship of advanced materials.Notably,this strategy has clear objectives and simple synthesis,which has made certain contributions to both theoretical research and future industrial production of proton conductors.
基金Project supported by the French Department of Defense(DGA)
文摘Electrical characterization analyses are proposed in this work using the Lambert function on Schottky junctions in GaN wide band gap semiconductor devices for extraction of physical parameters.The Lambert function is used to give an explicit expression of the current in the Schottky junction.This function is applied with defined conduction phenomena,whereas other work presented arbitrary(or undefined)conduction mechanisms in such parameters' extractions.Based upon AlGaN/GaN HEMT structures,extractions of parameters are undergone in order to provide physical characteristics.This work highlights a new expression of current with defined conduction phenomena in order to quantify the physical properties of Schottky contacts in AlGaN/GaN HEMT transistors.
基金financially supported by the National Natural Science Foundation of China under No.61971094Natural Science Foundation of Sichuan Province under Nos.2022NSFSC0485 and 2022NSFSC0870.
文摘High entropy oxides(HEO)are single-phase solid solutions which are formed by the incorporation of five or more elements into a cationic sublattice in equal or near-equal atomic proportions.Its unique structural features and the possibility of targeted access to certain functions have attracted great interest from researchers.In this review,we summarize the recent advances in the electronic field of high-entropy oxides.We emphasize the following three fundamental aspects of high-entropy oxides:(1)The conductivity mechanism of metal oxides;(2)the factors affecting the formation of single-phase oxides;and(3)the electrical properties and applications of high-entropy oxides.The purpose of this review is to provide new directions for designing and tailoring the functional properties of relevant electronic materials via a comprehensive overview of the literature on the field of high-entropy oxide electrical properties.
基金financially supported by the National Natural Science Foundation of China and the Israeli Science Foundation within the framework of the joint NSFC-ISF grant(No.51961145302)supported by the China Postdoctoral Science Foundation Project(No.2020M682403)。
文摘Almost unlimited reserves and low cost of sodium are accelerating the commercialization of sodiumion batteries.However,serious safety and stability issues,arising mainly from organic liquid electrolytes,hinder further developments of sodium-ion batteries.Polymer electrolytes might be a solution to the safety and stability issues due to the better safety of polymers.Herein,an overview is provided on recent advances in polymer electrolytes for solid-state sodium batteries,including solid polymer electrolytes,composite polymer electrolytes and gel polymer electrolytes.Fundamental properties,ionic conduction mechanisms and promising applications of polymer electrolytes are discussed,and pending challenges and effective solutions are emphasized.Hopefully,this review will promote commercial applications of polymer electrolytes in energy storage systems.
基金supported by the National Natural Science Foundation of China(Grant Nos.52072150 and 51972146)the Young Elite Scientists Sponsorship Program by CAST,the State Key Laboratory of New Ceramics and Fine Processing Tsinghua University(Grant No.KF202002)the Open Foundation of Guangdong Provincial Key Laboratory of Electronic Functional Materials and Devices(Grant No.EFMD2021002Z).
文摘The intrinsic conduction mechanism and optimal sintering atmosphere of(Ba_(0.85)Ca_(0.15))(Zr_(0.1)Ti_(0.9))O_(3)(BCZT)ceramics were regulated by Mn-doping element in this work.By Hall and impedance analysis,the undoped BCZT ceramics exhibit a typical n-type conduction mechanism,and the electron concentration decreases with the increasing oxygen partial pressure.Therefore,the undoped ceramics exhibit best electrical properties(piezoelectrical constant<733=585 pC·N^(-1),electro-mechanical coupling factor k_(p)=56%)in O_(2).A handful of Mn-doping element would transfer the conduction mechanism from n-type into p-type.And the hole concentration reduces with the decreasing oxygen partial pressure for Mn-doped BCZT ceramics.Therefore,the Mn-doped ceramics sintered in N_(2)have the highest insulation resistance and best piezoelectric properties(d_(33)=505 pC·N^(-1),k_(p)=50%).The experimental results demonstrate that the Mn-doping element can effectively adjust the intrinsic conduction mechanism and then predict the optimal atmosphere.
基金the National Science Foundation under Grant No.DMR-1308032Use of the Advanced Photon Source at Argonne National Laboratory was supported by the U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences,under Contract No.DE-AC02-06CH11357.
文摘Ceramics of the composition BaBiO_(3)(BB)were sintered in oxygen to obtain a single phase with monoclinic I2/m symmetry as suggested by high-resolution X-ray diffraction.X-ray photoelectron spectroscopy confirmed the presence of bismuth in two valence states—3þand 5þ.Optical spectroscopy showed presence of a direct bandgap at-2.2 eV and a possible indirect bandgap at-0.9 eV.This combined with determination of the activation energy for conduction of 0.25 eV,as obtained from ac impedance spectroscopy,suggested that a polaron-mediated conduction mechanism was prevalent in BB.The BB ceramics were crushed,mixed with BaTiO_(3)(BT),and sintered to obtain BT–BB solid solutions.All the ceramics had tetragonal symmetry and exhibited a normal ferroelectric-like dielectric response.Using ac impedance and optical spectroscopy,it was shown that resistivity values of BT–BB were orders of magnitude higher than BT or BB alone,indicating a change in the fundamental defect equilibrium conditions.A shift in the site occupancy of Bi to the A-site is proposed to be the mechanism for the increased electrical resistivity.
文摘Bis-Tetrapropylammonium tetrabromozincate was synthesized and characterized by X-ray powder diffraction,as well as vibrational and impedance spectroscopy.Rietveld’s refinement of X-ray diffractogram confirmed the crystallization of the compound through the monoclinic system(space group C_(2/c)).A temperature study of Raman scattering revealed two phase transitions at approximately T_(1)=340 K and T_(2)=393 K.The wavenumber and the line width’s evolution as a function of temperature showed some peculiarities associated with these transitions,which suggests that they are governed by the reorientation of the organic part[N(C_(3)H_(7))_(4)]+.The complex impedance plotted as a double semicircular arc in the studied temperature range and the centers of these semicircles lie below the real axis,which indicates that the material is an on-Debye type.These semicircular arcs are related to the bulk and the grain boundary effects.Furthermore,the alternating current conductivity of[N(C_(3)H_(7))_(4)]_(2)ZnBr_(4)obeyed Jonscher’s law:σ_(AC)(ω)=σ_(dc)+Aω^(s) and the conduction could be attributed to the correlated barrier hopping(CBH)model in both region(I)and(II)and the Non-overlapping Small Polaron Tunneling(NSPT)in region(III).
