Critical phenomena in order-disorder ferroelectrics. I. Calorimetric studies of KH(2)PO(4)
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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 transition. The divergence of the heat capacity may be interpreted as logarithmic, and if so, within experimental error the divergence is symmetric in the sense that the logarithmic slopes are the same above and below the transition. If the divergence is logarithmic, little significant evidence of rounding of the heat-capacity anomaly has been found to within a few millidegrees Ke!vin of the heat-capacity peak. It is also possible to interpret the data in terms of a power-law divergence, m which case the heat capacity associated with the transition behaves as (T,.-T)-0· 50 below the transition and as ( T-!,.)-1•04 .above the transition and the anomaly is rounded within about 0.05°K of either side of the heat-capacity maximum. The total transition entropy is found to be (0.422±0.014) R. Dielectric-constant measurements are also reported which may indicate that the temperature of the dielectric anomaly may be about 0.1°K lower than the temperature of the calorimetric anomaly.
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Studies of phase transitions in order-disorder ferroelectrics. II. Calorimetric investigation of KD(2)PO(4) Reese, W.; Dyer, J. N. (American Physical Society, 1968-03-10);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 ...
Benepe, J.W.; Reese, W. (American Physical Society, 1971-05-01);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 ...
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