Crystallographic characteristics and phase transitions in the [N(C2H5)(4)](2)CdBr4 crystal in the low-temperature range

摘要

The results of x-ray structural studies of the [N(C2H5)(4)](2)CdBr4 crystal at low temperatures are presented. The unit cell parameters and the thermal expansion coefficients along the main crystallographic directions are measured at temperatures in the range from 90 to 320 K. The integrated intensities of the diffraction reflections are investigated as a function of the temperature. It is shown that the curves a = f(T), c = f(T), I (500) = f(T), and I (006) = f(T) at temperatures T-1 approximate to 174 K and T-2 approximate to 226 K exhibit anomalies in the form of abrupt changes in the lattice parameters and the diffraction reflection intensities. This indicates that the [N(C2H5)(4)](2)CdBr4 crystal undergo phase transitions at these temperatures. Moreover, there is an anomaly in the form of a small maximum at the temperature T-3 = 293 K.