Antiferroelectric phase transitions in NH₄H₂AsO₄ and TlH₂AsO₄

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, T_L ). This result suggests a weak first-order antiferroelectric phase transition at T_L = 250.5 K in TlH₂AsO₄. Although the dielectric susceptibility above T_L does not follow a Curie-Weiss law, the antipolar characteristic below T_L was confirmed by hysteresis loop experiment.

Key Words:

• Antiferroelectric phase transition
• NH₄H₂AsO₄
• TlH₂AsO₄
• dielectric constant
• hysteresis loop