Design of Bismuth Layer-Structured Oxides with Regions of Different Electrical Properties

铋层状氧化物(BLSO)是由铋氧化物层和伪钙钛矿层组成的晶体结构，具有很强的各向异性，具有铁电和压电性能。在本研究中，我们生长了几种BLSO的单晶，并研究了晶体结构(铋层间氧八面体数目：m)与铁电性能之间的关系。结果表明，居里温度高的BLSO剩余极化较大，m较大的BLSO具有较小的矫直电场和较高的极化反转速度。本文制备了几种不同m的钙钛矿层交替堆积在晶格中的共生结构BLSO多晶，并研究了它们的铁电相变和铁电性能。M=1-2和2-3的共生BLSO在组份相变温度下有两次相变，m=3-4的共生BLSO在组份相变温度中点有一次相变。一些m=2-3和3-4的共生BLSO显示出比组分材料更高的剩余极化。

Bismuth layer-structured oxides (BLSOs) have the crystal structure composed of bismuth oxide layers and pseudo-perovskite layers, and known to show ferroelectric and piezoelectric properties with a strong anisotropy. In the present study, single crystals of several BLSOs were grown and correlations between crystal structure (the number of oxygen octahedron between bismuth layers : m) and ferroelectric properties were evaluated. It was found that the remanent polarization was larger in the BLSO with a high Curie temperature and the coercive electric field was smaller and the polarization reversal velocity was higher in BLSO with a large m. Polycrystals of several intergrowth structured BLSOs, in which perovskite layers with different m are stacked alternately in the lattice, were prepared and their ferroelectric phase transformations and ferroelectric properties were examined. The intergrowth BLSOs with m = 1-2 and 2-3 showed two phase transformations at temperatures of transformation of component materials, and that with m = 3-4 showed one transformation at the middle of transformation temperatures of component materials. Some of the intergrowth BLSOs with m = 2-3 and 3-4 was found to show a higher remanent polarization than those of component materials.