Ba_(0.98)Bi_(0.02)(Ti_(0.9)Zr_(0.1))_(1-x)Cu_xO_3陶瓷的介电弛豫特征

Dielectric Relaxation Properties of Ba_(0.98)Bi_(0.02)(Ti_(0.9)Zr_(0.1))_(1-x)Cu_xO_3 Ceramics

采用固相反应法制备Ba0.98Bi0.02(Ti0.9Zr0.1)1-xCuxO3(x=0,0.01,0.02,0.03,摩尔分数)陶瓷。X射线衍射分析结果表明:所有样品均为四方晶体结构,摩尔分数为2%的Cu2+能够完全溶入Ba0.98Bi0.02(Ti0.9Zr0.1)O3陶瓷晶格中。Ba0.98Bi0.02(Ti0.9Zr0.1)1-xCuxO3陶瓷不同频率的介电温谱显示:所有样品均具有弥散相变的特征,当x=0、0.02、0.03时,样品有典型弛豫铁电体的特征。当x=0.01时,剩余极化强度达到最大值,为2.83μC/cm,矫顽场达到最大值,为3.07 kV/cm。基于纳米极性微区和局域无规场的理论解释了弛豫铁电体和带有弥散相变的铁电体之间的关系,即当由价态差异和缺陷引发的局域无规场相对较强且测试频率与纳米极性微区的弛豫频率相近时,在弥散相变温度区间内的介电弛豫行为才能被观察到;而局域无规场很弱的情况下,介电弛豫行为只有在更高的频率下才能被观察到。

Ba0.98Bi0.02（Ti0.9Zr0.1）1-xCuxO3（x=0,0.01,0.02,0.03,mole fraction） ceramics were prepared by the solid state reaction process.The X-ray diffraction analysis indicates that all of ceramic samples have a tetragonal crystal structure,and 2%（in mole） Cu2＋ doping can be fully incorporated into the perovskite lattice of Ba0.98Bi0.02（Ti0.9Zr0.1）O3 ceramic.Dielectric constants vs temperature at different frequencies show that all of the ceramics have ferroelectrics characteristics with diffused phase transition,and the ceramic samples with x=0,0.02,0.03 exhibit typical relaxor ferroelectric characteristics.Maximum values of remnant polarization and coer-cive field are 2.83 μC/cm2 and 3.07 kV/cm at x=0.01.Relationships between ferroelectrics with diffused phase transitions and relaxor ferroelectrics based on the polar nanoregion model and local random field model were investigated.Dielectric relaxation can be ob-served when the local random field induced by the difference of the charge and defects are stronger,and test frequency is close to the relaxation frequency of the polar nanoregion at the temperature of the diffused phase transition.Comparatively speaking,dielectric relaxation can be observed at a higher test frequency when the local random field is weaker.