Electronic studies of KH(2)PO(4)

Abstract

The results of electrocaloric studies of the electrical equation of state of KH(2)PO(4) in the temperature region within 1 K of the ferroelectric transition are reported. Chief emphasis is given to determination of the spontaneous polarization. A discontinuous polarization jump of 1.87 ± 0.09 C/cm² is found at T(c). Several tests of the validity of the phenomenological theory of ferroelectricity, including a noncalorimetric determination of the heat capacity, are made. It is shown that the phenomenological theory provides a good and consistent description of the thermodynamic behavior of PH(2)PO(4). No major discrepancies which might be linked to behavior near a phase transition are found. Any possible discrepancies are minor and confined to the temperature region T(c) - T < 0.1 K. It is shown that a term proportional to P(8) dominates the behavior. Evidence is presented that a portion of the calorimetric anomaly near T(c) is not directly related to the temperature dependence of the polarization.