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Abstract
Dielectric properties of the new [NH(CH3)3]2ZnCl4 and [NH(CH3)3]2CdCl4 crystals from the [(CH3) n NH4-n ]2MeCl4 group have been investigated in a wide temperature range (4.2–320 K). A series of phase transitions has been discovered at T3 = 325 K,T4 = 251 K,T5 = 193 K, for [NH(CH3)3]2CdCl4 and at T3 = 309 K, T4 = 282 K, T5 = 269 K for [NH(CH3)3]2ZnCl4. A ferroelectric phase has been discovered in the temperature interval T4—T5 from the temperature and frequency dependence of the dielectric permittivity ε(T, v). According to optical investigations the existence of ferroelastic phases in the temperature interval T1 = 349 K–T2 = 391 K and below T5 for [NH(CH3)3]2CdCl4 and both above T3 and below T5 for [NH(CH3)3]2ZnCl4 has been ascertained.