Crystal lattice disorder and characteristic features of the low-temperature thermal properties of higher boridesстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 29 июля 2020 г.
Аннотация:Heat capacity C-P(T) and lattice parameters a(T), b(T) and c(T) of LuB44Si3.5 borosilicide are experimentally studied as a function of temperature in the range of 2-300 K. The results are compared with those of pseudo-isostructural LuB50 boride. At the lowest temperatures, it is shown that the C-P(T) dependence of borosilicide changes linearly with temperature. This is attributed to the effect of glass-like behaviour of the heat capacity due to the disorder in the sublattice of non-metals. The presence of defects in the B-Si sublattice and the irregular form of the cages in the B-Si matrix, which are occupied by Lu3+ ions, lead to the formation of two-level systems (TLS) in the Lu3+ subsystem. The TLS make a characteristic bell-like low-temperature contribution to the heat capacity of borosilicide. We show that there is a wide temperature range (5-150 K) of negative thermal expansion of borosilicide, which is attributed to the influence of quasi-independent vibrations of Lu3+ ions in the cages of the borosilicide crystal structure.