摘要
BaTiO_(3)具有高介低损、廉价环保的优点,但其介电常数在相变温度附近发生非线性变化的特性限制了其在宽温稳定型电容器领域的应用。为改善BaTiO_(3)的介温特性,本工作利用固相合成法制备BaTi_(1-x)Ce_(x)O_(3)(x=0~0.20)陶瓷,在BaTiO_(3)的B位(Ti位)引入Ce掺杂,通过实验方法研究不同Ce掺杂量对陶瓷相演变、缺陷状态、微观形貌与介电性能的影响规律,并结合第一性原理计算方法探究掺杂改性的作用机理。结果表明:在所有陶瓷样品中,Ce元素均以Ce 4+形式完全进入B位。随着Ce掺杂量的增加,BaTi_(1-x)Ce_(x)O_(3)陶瓷的室温结构由四方/赝立方共存结构转变为正交/四方结构,再转变为赝立方相结构。由于Ce 4+与Ti 4+的离子半径差异,Ce掺杂使得陶瓷的晶格常数上升,导致局部晶格畸变与铁电结构长程有序度的降低,引起能带结构、态密度与电荷密度分布的变化,并诱发Ba空位与Ti空位的生成。相较纯BaTiO_(3)陶瓷而言,Ce掺杂使得陶瓷的平均晶粒尺寸出现先减小后增加的变化规律,而陶瓷的致密度则逐渐上升。BaTi_(1-x)Ce_(x)O_(3)陶瓷的峰值介电常数随Ce掺杂量上升呈现先上升后下降的变化规律,其介电常数峰值温度在x=0~0.08成分区间内由122℃缓慢下降至112℃,而在x=0.08~0.20区间内快速下降至-3℃。具有x≥0.06取值的BaTi_(1-x)Ce_(x)O_(3)陶瓷表现出弥散相变的介电行为,而x=0.20陶瓷具有弛豫铁电体的典型特征,室温介电常数3258.38(10 kHz),|Δεr/εr25℃|≤22%的温度区间为-60~87℃,介温稳定性符合EIA X5S标准。由此可见,B位Ce掺杂可以有效改善BaTiO_(3)介电常数在变温环境中的稳定性,这将为研发宽温范围内具有稳定介电性能的介质材料提供新的思路。
BaTiO_(3)has advantages of high permittivity,low dielectric loss,low cost and environment friendly.However,due to the nonlinear dielectric behavior occurred around the phase transition temperature of BaTiO_(3)ceramic,its availability in the field of temperature-stable capacitor is limited.To modify the dielectric-temperature properties of BaTiO_(3),a series of BaTi_(1-x)Ce_(x)O_(3)(x=0-0.20)ceramics was synthesized by solid-state reaction method.Ce dopant was introduced into the B-site(Ti-site)of BaTiO_(3).The effects of Ce dopant on the phase evolution,defect state,microstructure and dielectric properties were investigated.The modifying mechanism was also discussed with the help of first-principles calculation method.In all ceramic samples,it is revealed that Ce element completely enters the B-site of BaTiO_(3)in the form of Ce 4+ion.With the increase of Ce doping concentration,the room temperature structure of BaTi_(1-x)Ce_(x)O_(3)ceramics transforms from tetragonal/pseudo-cubic structure into orthorhombic/tetragonal structure,then into pseudo-cubic structure.Owing to the radius difference between Ce 4+and Ti 4+ions,Ce doping will lead to the rising of lattice parameters,accompanied by the appearance of local distortion and the decrease of long-range ferroelectric order,the variation of band structure,density of states and charge density configuration,as well as the generation of Ba and Ti vacancies.Compared with pure BaTiO_(3)ceramic,the average grain size of Ce-doped ceramics decreases first and then increases with the increase of Ce content,while the relative density of ceramics increases gradually.The peak dielectric constant of BaTi_(1-x)Ce_(x)O_(3)ceramic increases first and then decreases as the Ce concentration increasing.The corresponding temperature is slowly reduced from 122℃to 112℃in the x value range of 0-0.08,then rapidly declines to-3℃in the x value range of 0.08-0.20.BaTi_(1-x)Ce_(x)O_(3)ceramics with x≥0.06 have the dielectric behavior of diffused phase transition(DPT).And the x=0.20 ceramic exhibits the typical characteristic of relaxor ferroelectric,with the room temperature dielectric constant of 3258.38,and the|Δεr/εr25℃|≤22%temperature range of-60-87℃,which matches the requirement of EIA X5S standard.Therefore,it can be concluded that B-site Ce doping will effectively enhance the permittivity stability of BaTiO_(3)in a variable temperature environment.This will provide some new ideas to develop dielectric materials with stable dielectric properties in wide temperature range.
作者
汪丰麟
毛海军
曹艳
席丽丽
白书欣
张为军
WANG Fenglin;MAO Haijun;CAO Yan;XI Lili;BAI Shuxin;ZHANG Weijun(College of Aerospace Science and Engineering,National University of Defense Technology,Changsha 410073,China;Materials Genome Institute,Shanghai University,Shanghai 200444,China)
出处
《材料工程》
EI
CAS
CSCD
北大核心
2023年第8期130-141,共12页
Journal of Materials Engineering
关键词
钛酸钡
铈
B位掺杂
结构特性
介电性能
BaTiO_(3)
cerium
B-site doping
structural characteristic
dielectric property
