Abstract (Cu6PS5Br)1-x(Cu7PS6)x mixed crystals were grown by chemical vapour transport. Low-temperature isoabsorption and polarisation studies of phase transitions (PT) were performed. A second-order PT characterized by appearance of light transmission in the polariser-crystal-analyser system and a typical knee at the isoabsorption dependence, is clearly revealed. With increasing Cu7PS6 content in (Cu6PS5Br)1-x(Cu7PS6)x mixed crystals, the second-order PT shifts down in temperature range and becomes smeared. Temperature behaviour of the optical absorption edge is studied in the temperature interval 77–320 K. In the superionic phase the absorption edge has an exponential shape and a characteristic Urbach bundle is observed. In the vicinity of the second-order PT, a variation of the Urbach absorption edge parameters and exciton-phonon interaction is revealed. Influence of compositional disordering on the parameters of the Urbach absorption edge, exciton-phonon interaction parameters, and the PT temperatures is studied.

中文翻译：

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(Cu 6 PS 5 Br) 1-x (Cu 7 PS 6 ) x 混晶中的相变和光吸收边

摘要 (Cu6PS5Br)1-x(Cu7PS6)x 混合晶体是通过化学气相传输生长的。进行了相变 (PT) 的低温等吸收和极化研究。清楚地揭示了二阶 PT，其特征在于偏振器-晶体-分析仪系统中的光透射外观和等吸收依赖性的典型拐点。随着 (Cu6PS5Br)1-x(Cu7PS6)x 混晶中 Cu7PS6 含量的增加，二阶 PT 在温度范围内向下移动并变得模糊。研究了 77-320 K 温度区间内光学吸收边的温度行为。在超离子相中，吸收边呈指数形状，并观察到特征 Urbach 束。在二阶 PT 附近，揭示了 Urbach 吸收边参数和激子-声子相互作用的变化。研究了成分无序对 Urbach 吸收边参数、激子-声子相互作用参数和 PT 温度的影响。