Electrical properties of a new mixed cesium–ammonium dihydrogen phosphate–arsenate: Cs0.55(NH4)0.45H2(PO4)0.39(AsO4)0.61

Abstract

Partial substitution of P by As and of Cs by NH4, leading to the solid solution Cs1-x(NH4)xH2(PO4) y (AsO4)1-y, with x = 0.45 and y = 0.39 (abbreviated as CADPA) has been shown. Two phase transitions at T 1 = 204 K and T 2 = 407 K were detected and studied by dielectric measurements and impedance and modulus spectroscopy. The evolution of the dielectric constant as a function of frequency and temperature revealed that the first transition (204 K) to be first order and antiferroelectric–paraelectric. The high-temperature phase transition (407 K) leads to a superionic protonic phase, characterized by an unusual high conductivity. The conductivity relaxation parameters associated with the high-disorder protonic conduction have been determined from analysis of the M″/M″ max spectrum measured in a wide temperature range. Transport properties in this material appear to be due to proton hopping mechanism.