Phase Transitions in Deuterated Compound {N(CD3)4}2CuBr4

Effect of deuteration on the phase transitions in tetramethylammonium tetrabromocuprate crystal was studied. At 1 atm. the deuterated compound {N(CD 3 ) 4 } 2 CuBr 4 shows three phase transitions at -2°C, -31°C, and -36°C on cooling, and it is ferroelectric between -31°C and -36°C. These transition temperatures almost coincide with those in the normal compound. The pressure-temperature phase diagram of the deuterated compound is also very close to that of the normal compound. Then the effect of deuteration on the phase transitions in tetramethylammonium tetrabromocuprate crystal is negligibly small making a sharp contrast with the considerable deuteration effects in ferroelectric tetramethylammonium tetrachlorozincate and -cobaltate crystals.