论文标题
晶体钙钛矿的精确多模式介电表征可确定温度依赖性相变
Precision Multi-Mode Dielectric Characterization of a Crystalline Perovskite Enables Determination of the Temperature-Dependent Phase Transitions
论文作者
论文摘要
简单的钙钛矿晶体在冷却至低温时会经历结构相变，这显着改变了晶体的材料特性。在这项工作中，我们严格地表征了钙钛矿晶体发生相变的介电常数的温度演变。特别是，我们通过同时测量多个微波横向电和磁性谐振模式的频率来对钛酸锶的单个晶体的精确测量进行精确测量。在这项工作中使用的谐振频率的多模式微波测量技术允许高精度确定介绍性的任何诱导的各向异性，因为晶体经历了结构相变。与先前的结果相比，我们明确地表明，在室温下，介电常数的各向同性值为$ 316.3 \ pm2.2 $，与其众所周知的立方结构一致，并确定介电各向异性的发作，因为晶体冷却以降低频率。我们表明，当结构变为四方时，晶体在低于105 k的介电常序中表现出单轴各向异性，当结构变为正交时，在51 K以下的介电常数中表现出双轴各向异性。
Simple perovskite crystals undergo structural phase transitions on cooling to low temperatures, which significantly change the material properties of the crystal. In this work we rigorously characterize the temperature evolution of permittivity of a perovskite crystal as it undergoes phase transitions. In particular, we have undertaken precision measurements of a single crystal of Strontium Titanate from 294.6 K to 5.6 K, by measuring the frequency of multiple microwave transverse electric and magnetic resonant modes simultaneously. The multi-mode microwave measurement technique of resonant frequency used in this work allows high precision determination of any induced anisotropy of the permittivity as the crystal undergoes structural phase transitions. Compared with previous results we unequivocally show that the permittivity has an isotropic value of $316.3\pm2.2$ at room temperature, consistent with its well-known cubic structure, and determine the onset of dielectric anisotropy as the crystal is cooled to lower temperatures. We show that the crystal exhibits uniaxial anisotropy in the permittivity below 105 K when the structure becomes tetragonal, and exhibits biaxial anisotropy in the permittivity below 51 K when the structure becomes orthorhombic.
