Spontaneous polarization in the deuterated and undeuterated proton glass Rb1-x(NH4)xH2AsO4

Abstract

Spontaneous polarization of mixed single crystals of Rubidium Ammonium Dihydrogen Arsenate (RADA) and its deuterated counterpart (DRADA) are presented together with the pure ferroelectric Rubidium Dihydrogen Arsenate (RDA) and its deuterated counterpart (DRDA). There is a sharp rise in the spontaneous polarization at the ferroelectric transition temperature Tc for the pure crystals as this transition is first order. The change in the spontaneous polarization in the mixed (x = 0.08) crystals below Tc is gradual however, indicating the presence of acid hydrogens and ammonium cations that are still mobile and in the paraelectric phase. These mixed crystals show coexistence of paraclectric/proton glass and ferroelectric order below the glass “transition” temperature Tg. The maximum values of the spontaneous polarization in the deuterated samples are greater than in the undeuterated samples. Also, the maximum values of the spontaneous polarization in mixed crystals below 1c. at the lowest temperatures reported is found to be slightly lower than the corresponding values in the pure crystals.