Antiferroelectric phase transitions in NH₄H₂AsO₄and TlH₂AsO₄

Abstract

Abstract The phase transitions of NH4H2AsO4 single crystal and TlH2AsO4 powder pellet have been investigated by dielectric measurements and D-E hysteresis loops studies. The dielectric anomaly of TlH2AsO4 near 250.5K was very similar to that of TlH2PO4 undergoing the antiferroelectric transition at 230 K (the lower phase transition point, TL ). This result suggests a weak first-order antiferroelectric phase transition at TL = 250.5 K in TlH2AsO4. Although the dielectric susceptibility above TL does not follow a Curie-Weiss law, the antipolar characteristic below TL was confirmed by hysteresis loop experiment.