The solid solutions of In^(3+) doped M-type strontium hexaferrites were produced using a conventional solid-state reaction method,and Rietveld analysis of the neutron diffraction patterns was conducted.In^(3+) cations...The solid solutions of In^(3+) doped M-type strontium hexaferrites were produced using a conventional solid-state reaction method,and Rietveld analysis of the neutron diffraction patterns was conducted.In^(3+) cations occupy octahedral (4f_(Ⅵ)and 12 k) and tetrahedral (4f_(Ⅳ)) positions (SG=P6_(3)/mmc(No.194)).The average particle size is 837–650 nm.Curie tempearature (T_(C)) of the compounds monotonically decreased down to~520 K with increasing x.A frustrated magnetic state was detected from ZFC and FC magnetizations.saturation magnetization (M_(s)) and effective magnetocrystalline anisotropy coefficient (k_(eff)) were determined using the law of approach to saturation.A real permittivity (ε″) maximum of~3.3 at~45.5 GHz and an imaginary permittivity (ε′) of~1.6 at~42.3 GHz were observed for x=0.1.A real permeability (μ′) maximum of~1.5 at~36.2 GHz was observed for x=0.Aμ″imaginary permeability maximum of~0.8 at~38.3 GHz was observed for x=0.1.The interpretation of the results is based on the type of dielectric polarization and the natural ferromagnetic resonance features.展开更多
A new thermoelectric material Ag8SnS6, with ultra-low thermal conductivity in thin film shape, is prepared on indium tin oxide coated g/ass （ITO） substrates using a chemical process via the electrodeposition techniq...A new thermoelectric material Ag8SnS6, with ultra-low thermal conductivity in thin film shape, is prepared on indium tin oxide coated g/ass （ITO） substrates using a chemical process via the electrodeposition technique. The structural, thermal and electrical properties are studied and presented in detail, which demonstrate that the material is of semiconductor type, orthorhombic structure, with a band gap in the order of 1.56eV and a free carrier concentration of 1.46 × 10^17 cm-3. The thermal conductivity, thermal diffusivity, thermal conduction mode, Seebeck coefficient and electrical conductivity are determined using the photo-thermal deflection technique combined with the Boltzmann transport theory and Cahill＇s model, showing that the AgsSnS6 material has a low thermal conductivity of 3.8 Wm - 1K- 1, high electrical conductivity of 2.4 × 10^5 Sm- 1, Seebeck coefficient of -180μVK-1 and a power factor of 6.9mWK-2m-1, implying that it is more efficient than those obtained in recently experimental investigations for thermoelectric devices.展开更多
Yttrium aluminium garnet(Y3Al5O12:YAG) singly doped with Dy3+ at different concentrations was prepared by solid state reactions using repeated heating cycles over the temperature range of 1300-1600 ℃. X-ray powder di...Yttrium aluminium garnet(Y3Al5O12:YAG) singly doped with Dy3+ at different concentrations was prepared by solid state reactions using repeated heating cycles over the temperature range of 1300-1600 ℃. X-ray powder diffraction analysis confirms the presence of a well-crystallized YAG perovskite phase with cubic structure(by Rietveld refinement). The rare earth dopant is successfully integrated into the YAG host lattice without any major changes in the original structure. The temperature dependence,up to 250 ℃, of the conductivity, dielectric constant, dielectric loss, and loss tangent, at various frequencies of up to 5.0 MHz for undoped and doped crystals is compared to understand the electrical and structural characteristics. The experimental results reveal that Dy3+ dopants in YAG crystal significantly influence the conductivity, dielectric constant, and lossy mechanisms, which is probably due to the 3 d-AI ions and 4 f-Dy ions incorporated at different positions of both tetrahedral and octahedral symmetries in YAG:xDy3+ ceramics.展开更多
Spinel ferrite Co1-2 xNixMnxFe2-yCeyO4(0.0≤x=y≤0.3) nanoparticles(NPs) were prepared by sol-gel auto-combustion method.The synthesized NPs were examined using several techniques such as X-ray diffraction(XRD),field ...Spinel ferrite Co1-2 xNixMnxFe2-yCeyO4(0.0≤x=y≤0.3) nanoparticles(NPs) were prepared by sol-gel auto-combustion method.The synthesized NPs were examined using several techniques such as X-ray diffraction(XRD),field emission scanning electron microscopy(FE-SEM) coupled with EDX and elemental mapping,transmission electron microscopy(TEM),Fourier-transform infrared spectroscopy(FT-IR),and a vibrating sample magnetometer(VSM).The analysis of the crystal structure and the phase identification of samples indicates the formation of spinel cubic phase with the occurrence of CeO2 as secondary phase when the content of Ce substitution element increases.In addition,all produced samples exhibit cubic symmetry with space group Fd3m.TEM confirms the presence of two phases,i.e.,the cubic spinel ferrite and the cubic cerium oxide(CeO2).The characteristics of hysteresis loops reveal the soft ferrimagnetic nature of the different synthesized samples.The saturation(Ms) and remanent(Mr) magnetizations fall on increasing the content of substituting elements.Compared with pure CoFe2O4 NPs,the value of coercive field(Hc) slightly increases for x=y=0.1 and x=y=0,2 NPs.Then,Hc reduces with further increasing the x and y contents.The squareness ratio is found to be in the 0.528-0.400 interval,indicating the single domain NPs with uniaxial anisotropy for the different produced NPs.The magneto crystalline anisotropy constant(Keff),anisotropy field(Ha),magneton number(nB) and the demagnetizing field(N) were also determined and discussed.展开更多
基金conducted with financial support from the Russian Science Foundation (Agreement No. 19-19-00694 of 06 May 2019)。
文摘The solid solutions of In^(3+) doped M-type strontium hexaferrites were produced using a conventional solid-state reaction method,and Rietveld analysis of the neutron diffraction patterns was conducted.In^(3+) cations occupy octahedral (4f_(Ⅵ)and 12 k) and tetrahedral (4f_(Ⅳ)) positions (SG=P6_(3)/mmc(No.194)).The average particle size is 837–650 nm.Curie tempearature (T_(C)) of the compounds monotonically decreased down to~520 K with increasing x.A frustrated magnetic state was detected from ZFC and FC magnetizations.saturation magnetization (M_(s)) and effective magnetocrystalline anisotropy coefficient (k_(eff)) were determined using the law of approach to saturation.A real permittivity (ε″) maximum of~3.3 at~45.5 GHz and an imaginary permittivity (ε′) of~1.6 at~42.3 GHz were observed for x=0.1.A real permeability (μ′) maximum of~1.5 at~36.2 GHz was observed for x=0.Aμ″imaginary permeability maximum of~0.8 at~38.3 GHz was observed for x=0.1.The interpretation of the results is based on the type of dielectric polarization and the natural ferromagnetic resonance features.
基金Supported by the Scientific Research Deanship of University of Dammam under Grant No 2014264
文摘A new thermoelectric material Ag8SnS6, with ultra-low thermal conductivity in thin film shape, is prepared on indium tin oxide coated g/ass （ITO） substrates using a chemical process via the electrodeposition technique. The structural, thermal and electrical properties are studied and presented in detail, which demonstrate that the material is of semiconductor type, orthorhombic structure, with a band gap in the order of 1.56eV and a free carrier concentration of 1.46 × 10^17 cm-3. The thermal conductivity, thermal diffusivity, thermal conduction mode, Seebeck coefficient and electrical conductivity are determined using the photo-thermal deflection technique combined with the Boltzmann transport theory and Cahill＇s model, showing that the AgsSnS6 material has a low thermal conductivity of 3.8 Wm - 1K- 1, high electrical conductivity of 2.4 × 10^5 Sm- 1, Seebeck coefficient of -180μVK-1 and a power factor of 6.9mWK-2m-1, implying that it is more efficient than those obtained in recently experimental investigations for thermoelectric devices.
文摘Yttrium aluminium garnet(Y3Al5O12:YAG) singly doped with Dy3+ at different concentrations was prepared by solid state reactions using repeated heating cycles over the temperature range of 1300-1600 ℃. X-ray powder diffraction analysis confirms the presence of a well-crystallized YAG perovskite phase with cubic structure(by Rietveld refinement). The rare earth dopant is successfully integrated into the YAG host lattice without any major changes in the original structure. The temperature dependence,up to 250 ℃, of the conductivity, dielectric constant, dielectric loss, and loss tangent, at various frequencies of up to 5.0 MHz for undoped and doped crystals is compared to understand the electrical and structural characteristics. The experimental results reveal that Dy3+ dopants in YAG crystal significantly influence the conductivity, dielectric constant, and lossy mechanisms, which is probably due to the 3 d-AI ions and 4 f-Dy ions incorporated at different positions of both tetrahedral and octahedral symmetries in YAG:xDy3+ ceramics.
基金the Institute for Research & Medical Consultations(IRMC)of Imam Abdulrahman Bin Faisal University(IAU-Saudi Arabia)for supporting this study through the Projects application No.2017-IRMC-S-3,No.2018-IRMC-S-1 and No.2018-IRMC-S-2.
文摘Spinel ferrite Co1-2 xNixMnxFe2-yCeyO4(0.0≤x=y≤0.3) nanoparticles(NPs) were prepared by sol-gel auto-combustion method.The synthesized NPs were examined using several techniques such as X-ray diffraction(XRD),field emission scanning electron microscopy(FE-SEM) coupled with EDX and elemental mapping,transmission electron microscopy(TEM),Fourier-transform infrared spectroscopy(FT-IR),and a vibrating sample magnetometer(VSM).The analysis of the crystal structure and the phase identification of samples indicates the formation of spinel cubic phase with the occurrence of CeO2 as secondary phase when the content of Ce substitution element increases.In addition,all produced samples exhibit cubic symmetry with space group Fd3m.TEM confirms the presence of two phases,i.e.,the cubic spinel ferrite and the cubic cerium oxide(CeO2).The characteristics of hysteresis loops reveal the soft ferrimagnetic nature of the different synthesized samples.The saturation(Ms) and remanent(Mr) magnetizations fall on increasing the content of substituting elements.Compared with pure CoFe2O4 NPs,the value of coercive field(Hc) slightly increases for x=y=0.1 and x=y=0,2 NPs.Then,Hc reduces with further increasing the x and y contents.The squareness ratio is found to be in the 0.528-0.400 interval,indicating the single domain NPs with uniaxial anisotropy for the different produced NPs.The magneto crystalline anisotropy constant(Keff),anisotropy field(Ha),magneton number(nB) and the demagnetizing field(N) were also determined and discussed.
