Studies of phase transitions in order-disorder ferroelectrics. III. The phase transition in KH(2)PO(4) and a comparison with KD(2)PO(2)
MetadataShow full item record
Calorimetric, dielectric, and electrocaloric measurements have been performed on single-crystal samples of KH(2)PO(4) in the neighborhood of the ferroelectric phase transition, and show that the transition is of first order, with a discontinuous entropy change of (0.0456-0.00069)(+0.0046)R and a change in the dielectric constant by a factor of 2. Calorimetric measurements in applied electric fields were also carried out, and show that the effect of an applied field is to shift the transition to higher temperatures and to broaden it. Calorimetric measurements on KD(2)PO(4) are reported which can be combined with previously reported results to give the heat capacity for this material in the range 80-280°K. Comparison of the heat capacity of KH(2)PO(4) and its deuterated isomorph allows estimates of the lattice heat capacity to be made. From this estimate, the entropy change associated with the ferroelectric transition is found to be (0.400±0.036)R for KH,PO(4) and (0.457±0.034)R for KD(2)PO(4). A significant feature of the comparison is the lack of evidence for the heat-capacity contribution above the transition predicted by theories of .the Slater type. Comparison of the calorimetric data with the modified Slater theory due to Silsbee, Uehling, and Schmidt shows that this theory describes KD(2)PO(4) better than it does KH(2)PO(4). The differences between the theory and experiment are of the type predicted by the modifications of the theory which include tunneling motion of the protons.
RightsThis publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.
Showing items related by title, author, creator and subject.
Studies of phase transitions in order-disorder ferroelectrics. II. Calorimetric investigation of KD(2)PO(4) Reese, W.; Dyer, J. N. (American Physical Society, 1968);Calorimetric measurements on KD(2)PO(4) have been conducted, and the transition is found to be first order with an entropy change at T(c) of (0.2407+/- 0.0016)R. The entropy change associated with destruction of the ...
Reese, W.; May, L.F. (American Physical Society, 1967);High-resolution measurements of the heat capacity in the immediate neighborhood of the ferroelectric transition in KH2P04 are reported. The heat-capacity anomaly is interpreted as a second-order, or nearly second-order ...
Espiritu, Jed R. (Monterey California. Naval Postgraduate School, 2004);This thesis seeks to determine how the naval shipyards could better implement mission funding after having worked extensively under a Working Capital Fund structure. Several principles exist in current management literature ...