Origin and stability of the dipolar response in a family of tetragonal tungsten bronze relaxors
Origin and stability of the dipolar response in a family of tetragonal tungsten bronze relaxors
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DOI：
10.1103/physrevb.83.184302
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发表时间：
2011-04
影响因子：
3.7
通讯作者：
A. Rotaru;D. Arnold;A. Daoud-Aladine;F. Morrison
中科院分区：
文献类型：
--
作者：
A. Rotaru;D. Arnold;A. Daoud-Aladine;F. Morrison
用介电谱研究了一个新的具有四钨青铜结构的弛豫型晶体（名义成分为Ba 6 M3 + Nb 9 O 30，M3+ = Ga，Sc，或In），以探测动态偶极响应，并将其与粉末中子衍射确定的晶体结构相关联。对复介电函数的真实的部分和虚部的独立分析分别用于确定特征温度参数TVF和TUDR。在每种组合物中，这两个温度与最大晶体应变的温度，Tc/a，从衍射数据确定。整体行为与偶极冻结一致，并且数据表明，由于晶胞的四方性增加，偶极稳定性随着M3+阳离子尺寸的增加而增加。晶体学数据表明，这些材料是单轴弛豫的偶极矩主要限于B1阳离子网站的结构。弛豫行为的可能起源进行了讨论。
A new family of relaxor dielectrics with the tetragonal tungsten bronze structure (nominal composition Ba6M3+Nb9O 30, M3+ = Ga, Sc, or In) were studied using dielectric spectroscopy to probe the dynamic dipole response and correlate this with the crystal structure as determined from powder neutron diffraction. Independent analyses of real and imaginary parts of the complex dielectric function were used to determine characteristic temperature parameters, TVF and TUDR, respectively. In each composition both these temperatures correlated with the temperature of maximum crystallographic strain, T c/a, determined from diffraction data. The overall behavior is consistent with dipole freezing and the data indicate that the dipole stability increases with increasing M3+ cation size as a result of increased tetragonality of the unit cell. Crystallographic data suggests that these materials are uniaxial relaxors with the dipole moment predominantly restricted to the B1 cation site in the structure. Possible origins of the relaxor behavior are discussed.