Thermodynamic properties of KH(2)AsO(4) and KD(2)As0(4)

Abstract

Measurement of the specific heat and electric susceptibility of KH(2)AsO(4) and KD(2)AsO(4) have been performed in the region of their respective ferroelectric transitions. Both substances undergo first-order transitions with latent heat of 300 and 570 J/mole, respectively. The entropy associated with the transition is found to be 0.506R and0,500R respectively. The Curie constants are found to be 187 and 358 K, respectively. The thermal data are used to deduce the spontaneous polarization. The polarization then deduced agrees with electrocaloric data for KH(2)AsO(4), the only case where independent polarization data are available. The maximum spontaneous polarizations are found to be 5.25 and 7.20 uC/cm2, respectively. It is shown that the theory of Silsbee, Uehling and Schmidt provides an excellent description of the thermodynamic properties of both materials.