Crystal Structure of [N(CH 3 ) 4 ] 2 CuBr 4

The crystal structure of [N(CH 3 ) 4 ] 2 CuBr 4 was studied at 90, 70, 50, 38, 25°C in the paraelectric phase and at -33.5°C in the ferroelectric phase by the use of the data collected by a four-circle diffractometer. From the large values of temperature parameters of constituent atoms in the paraelectric phase and their variation with temperature we propose a model that all the constituent ions are in disorder in the paraelectric phase. In the ferroelectric phase(-33.5°C), the ions are almost in order. Structure of [N(CH 3 ) 4 ] 2 ZnCl 4 in the paraelectric and ferroelectric phases is referred for comparison.