The Role of Spontaneous Polarization in the Negative Thermal Expansion of Tetragonal PbTiO3-Based Compounds
The Role of Spontaneous Polarization in the Negative Thermal Expansion of Tetragonal PbTiO3-Based Compounds
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自发极化在四方 PbTiO3 基化合物负热膨胀中的作用
DOI：
10.1021/ja2046292
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发表时间：
2011-07-27
影响因子：
15
通讯作者：
Xing, Xianran
中科院分区：
文献类型：
--
作者：
Chen, Jun;Nittala, Krishna;Xing, Xianran
基于PbTiO 3的化合物是公知的铁电体，其在四方相中或多或少地表现出负热膨胀。本文用高温中子粉末衍射方法研究了两种具有代表性的化合物0.7PbTiO（3）-0.3BiFeO（3）和0.7PbTiO（3）-0.3Bi（Zn_（1/2）Ti_（1/2））O_3的负热膨胀效应，它们的负热膨胀效应分别相反地增强和减弱。当温度升高到居里温度时，0.7PbTiO（3）-0.3BiFeO（3）中Pb/Bi的自发极化位移（Δ z（pb/Bi））减弱，而0.7PbTiO（3）-0.3Bi（Zn 1/2 Ti 1/2）O-3中Pb/Bi的自发极化位移（Δ z（pb/Bi））保持良好。四角性（c/a）与自发极化有明显的相关性。直接的实验证据表明，源于Pb/Bi-O杂化的自发极化与负热膨胀密切相关。这一机理可为今后相变氧化物负热膨胀材料的设计提供指导。
PbTiO3-based compounds are well-known ferroelectrics that exhibit a negative thermal expansion more or less in the tetragonal phase. The mechanism of negative thermal expansion has been studied by high-temperature neutron powder diffraction performed on two representative compounds, 0.7PbTiO(3)-0.3BiFeO(3) and 0.7PbTiO(3)-0.3Bi(Zn1/2Ti1/2)O-3, whose negative thermal expansion is contrarily enhanced and weakened, respectively. With increasing temperature up to the Curie temperature, the spontaneous polarization displacement of Pb/Bi (delta z(pb/Bi)) is weakened in 0.7PbTiO(3)-0.3BiFeO(3) but well-maintained in 0.7PbTiO(3)-0.3Bi(Zn1/2Ti1/2)O-3. There is an apparent correlation between tetragonality (c/a) and spontaneous polarization. Direct experimental evidence indicates that the spontaneous polarization originating from Pb/Bi-O hybridization is strongly associated with the negative thermal expansion. This mechanism can be used as a guide for the future design of negative thermal expansion of phase-transforming oxides.