Phase Transformation Seen Through"Millikelvin-Stabilized Cell"―Detection by X-ray Diffraction―

通过“毫开尔文稳定池”观察相变——X射线衍射检测——

• 批准号: 10640317
• 负责人: YOSHIMURA Yukio
• 金额: $ 2.11万
• 依托单位: Ritsumeikan University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1998
• 资助国家: 日本
• 起止时间: 1998 至 1999
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10640317/
• 关键词: simultaneous temperature, DC calorimeter and X-ray diffraction measurements; structural phase transition; "millikelvin-stabilized cell"; phase transition of CsPbClィイD23ィエD2; phase transitionof BaTiOィイD23ィエD2; X線回折実験; CsPbCl_3の相転移; BaTiO_3の相転移; 温度-; simultaneous temperature, DC calorimeter and X-ray diffraction measurements; structural phase transition; "millikelvin-stabilized cell"; phase transition of CsPbClィイD23ィエD2; phase transitionof BaTiOィイD23ィエD2; X線回折実験; CsPbCl_3の相転移; BaTiO_3の相転移; 温度-

A Simple and versatile"millikelvin-stabilized cell" has been developed to investigate phase transformation stage in solid precisely. It can be used as a fine DC calorimeter and also, by mounting on a goniometer head, as an X-ray diffraction cell with a function of sensing thermal anomaly. When applied to the well known 320 K phase transformation in CsPbClィイD23ィエD2, it was found that it occurs not in a single-stage but in a hyperfine multistage in the temperature range of approximately 0.1 K.The results required a reinterpretation of the mechanism on the successive phase transition of the crystal. In order to make clear the hyperfine multistage transition, we have reexamined the phase changes of the crystal over wide temperature range, 340 K-90 K, by means of single crystal X-ray photographic method. On cooling from room temperature, it was found that at about 265K, an abrupt increase of intensity was observed at 0 k 1+ 1/2 superlattice reflections corresponding to the X-point in the cu … More bic Brilloun zone. With lowering temperature further to 200 K, another abrupt increase of intensity was observed at h+1/2 k+1/2 1+1/2 superlattice reflections which correspond to the R-point. The anomaly at the 200K, although accompanies with conspicuous splitting of the h k 1Bragg spots along [010]c* direction, weak spots without splitting were still observed. These facts indicated that a coexistence of two crystal forms exists in the lowest temperature phase below 200 K. One is a monoclinic form and the other is tetragonal one. The results in this study suggests that the crystal undergoes two series of successive structural changes starting from the superfine anomalies at the 320 K transition. One is 320―315―310 K transition series (series" II") which is related to the so called soft phonon condensation theory, and the other is 320―265―200 K transition series, series "I", which is however dominant in the specimen.The 408 K phase transformation in BaTiOィイD23ィエD2 by means of "millikelvin-stabilized cell" was also revealed to occur in multistage. An anomalous transition was also detected in (KCN)x(KBr) ィイD21-xィエD2 mixed crystal in advance study on the phase transition. Application of the "millikelvin-stabilized cell" to the precise study on the phase transition is now planned on these crystals. Less

已经开发了一个简单且通用的“ Millikelvin稳定细胞”，以精确地研究固体中的相变阶段。它可以用作精细的直流量热仪，还可以通过安装在Goniometer头上，用作具有感应热异常的函数的X射线衍射细胞。当应用于CSPBCLI D23E D2中众所周知的320 K相变时，发现它不是在单个阶段中发生，而是在大约0.1 K的温度范围内发生的超精美多阶段。结果需要重新解释晶体成功相变的机制。为了清除超精细的多阶段过渡，我们通过单晶X射线摄影方法重新审查了宽温度范围340 K-90 K的晶体的相变。从室温冷却时，发现在约265K时，在0 K 1+ 1/2的超晶格反射下突然增加了强度，对应于Cu中的X-Point…更多BIC Brilloun区域。随着温度进一步降低到200 k，在H+1/2 K+1/2 1+1/2超晶格反射时，强度的突然突然增加与对应于R-Point相对应。尽管沿[010] c*方向对H k 1bragg斑点的明显分裂涉及到200K的异常，但仍观察到弱点，而没有分裂。这些事实表明，两种晶体形式的共存存在于低于200 K的最低温度相。一种是单斜形形式，另一种是四方。这项研究的结果表明，晶体经历了从320 K过渡时超细异常开始的两个成功的结构变化。 One is 320-315-310 K transition series (series" II") which is related to the so called soft The phonon condensation theory, and the other is 320-265-200 K transition series, series "I", which is however dominant in the specimen.The 408 K phase transformation in BaTiOi D23i D2 by means of "millikelvin-stabilized cell" was also revealed to occur in multistage.在（KCN）X（kbr）D21-XIE D2混合晶体中，还检测到异常的转变。现在计划在这些晶体上应用“ Millikelvin稳定的细胞”对相变精度研究的应用。较少的