ABSTRACT

The GeTe-GeBi₂Te₄ part of the GeTe-Bi₂Te₃ quasi-binary system was re-examined in the 700-1000 K temperature interval by using PXRD, DTA, and SEM techniques, and the corresponding fragment of the phase diagram was constructed. The existence of 4 ternary compounds is confirmed in the system. Ge₂Bi₂Te₅ (863 K) and GeBi₂Te₄ (854 K) compounds formed by peritectic reactions, while Ge₃Bi₂Te₆ and Ge₄Bi₂Te₇ decompose by solid-phase reactions. The system is also characterized by the formation of large areas of solid solutions based on both modifications of GeTe. Besides, rhombohedral→cubic morphotropic phase transition occurs between 9 and 10 mol% Bi₂Te₃ compositions. The homogeneity field of the cubic phase does not exceed 2-3 mol% at 700 K and layered phases are formed as the concentration of Bi₂Te₃ increases. Crystallographic parameters of ternary compounds, as well as solid solutions, were determined by the Rietveld method. A comparative analysis of obtained results with literature data is performed.

摘要

GeTe-Bi ₂ Te ₃准二元体系的GeTe-GeBi ₂ Te ₄部分在700-1000 K温度区间通过使用PXRD、DTA和SEM技术以及相图的相应片段进行了重新检查被建造。系统中确认了4种三元化合物的存在。包晶反应形成的Ge ₂ Bi ₂ Te ₅ (863 K)和GeBi ₂ Te ₄ (854 K)化合物，而Ge ₃ Bi ₂ Te ₆和Ge ₄ Bi ₂ Te ₇通过固相反应分解。该系统的特征还在于基于 GeTe 的两种变体形成大面积的固溶体。此外，菱形→立方同形相变发生在 9 和 10 mol% Bi ₂ Te ₃组成之间。立方相的均匀场在 700 K 下不超过 2-3 mol%，并且随着 Bi ₂ Te ₃浓度的增加形成层状相。三元化合物以及固溶体的结晶参数通过 Rietveld 方法确定。对获得的结果与文献数据进行比较分析。