Measurements of the spontaneous polarization in KH(2)PO(2)

Measurements of the spontaneous polarization of KH(2)PO(4) within 1 K if the ferroelectric transition are reported. the measurement employed the electrocaloric effect, allowing simultaneous determination of the polarization and its temperature derivative. The derivative computed from polarization measurements compares well with direct determinations of (OP/OT)e, demonstrating thermodynamic consistency of the measurements. The transition is first order with a discontinuous jump in the polarization of 1.87 uc/cm(2) at the transition. Laudau theory allows separate calculation at specific heat contributions of the lattice and polarization and thus the total specific heat, which agrees very well with direct calorimetric determinations, although the decomposition differs from that previously assumed. This indicates that Landau theory provides a good description of the transition in KH(2)PO(4) and that there is a calorimetric anomaly not directly associated with the polarization. The free energy expansion best fitting the data contains P(4) and P(8) terms and no P(6) term. http://archive.org/details/measurementsofsp1094515086 Lieutenant Commander, United States Navy Approved for public release; distribution is unlimited.