Pyroelectric and dilatometric studies on [nh2(ch3)213sb2x9(x =cl, br)

Pyroelectric and dilatometric properties of isomorphous crystals; [NH2(CH3)2]3Sb2Cl9 (DMACA) and [NH2(CH3)2]3Sb2Br9 (DMABA) have been compared. A nontypical temperature behaviour of P, (T) in both dimethylammonium crystals was found. The paraelectric effect has been observed down to liquid helium temperature. The dilatometric measurements corroborate the continuous ferro-paraelectric phase transition both for DMACA and DMABA.