Journal ArticleDOI
Theory of the Transition in KH2PO4
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In this paper, the theory of spontaneous polarization along the axis of the crystal, resulting in a well-known transition, similar to Rochelle salt, with polarization below the Curie point was worked out.Abstract:
Potassium dihydrogen phosphate contains phosphate groups connected by hydrogen bonds. Different possible arrangements of the hydrogens result effectively in different orientations of the (H2PO4)— dipoles. Since these have the lowest energy when pointing along the axis of the crystal, there is a tendency toward spontaneous polarization along this axis, resulting in the well‐known transition, similar to Rochelle salt, with polarization below the Curie point. The theory of this transition is worked out, using statistical methods to count the number of arrangements of hydrogens consistent with each total polarization of the crystal, and deriving the free energy. It is found that the theory predicts a phase change of the first order, with sudden transition from the polarized state at low temperature to the unpolarized state at high temperature, rather than the lambda‐point transition or phase change of the second order which is observed. However, the observed transition is confined to a very narrow temperature range compared to that predicted, for instance, by the Weiss theory, so that it seems as if it might be merely a broadened transition of the first order. It is suggested that the broadening may result from the irregular shifts of transition temperatures of individual domains in the crystal on account of stresses resulting from the large piezoelectric effect and the resulting deformation of the crystal below the transition point. The susceptibility above the Curie point comes out by the theory to be 4.33 times as great as it should according to the Weiss theory, a result which seems to be in general agreement with experiment. The entropy change in the transition is given by the theory as 0.69 unit, somewhat smaller than the observed value of about 0.8 unit. No explanation is suggested for this discrepancy.read more
Citations
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Journal ArticleDOI
Pressure dependence of the static and dynamic properties of KH2PO4 and related ferroelectric and antiferroelectric crystals
TL;DR: A summary of the effects of hydrostatic pressure on the properties of KDP and related crystals is presented in this article with some emphasis on recent results, including the decrease and ultimate vanishing of Tc with pressure, the underdamped soft mode, the strong deuteration dependence of the pressure effects, the pressure-induced tricritical point in KDP, the unusual pressure behavior of CsH2PO4 and CsD2PO 4, the proton glass behavior of Rb,1-x(NH4)xH 2PO4 mixed crystals, and
Book ChapterDOI
The Study of Soft-Mode Transitions at High Pressure
George A. Samara,P.S. Peercy +1 more
TL;DR: In this article, a study on soft-mode transitions at high pressure is presented, where the authors present a brief theoretical background with some of the essential results needed for the interpretation.
Journal ArticleDOI
First‐Order Ferroelectric Transition in (NH4)2SO4
D. E. O'Reilly,Tung Tsang +1 more
TL;DR: In this article, a modified molecular field approximation of (NH4)2SO4 is presented in which a dependence of the interaction parameters on the number of misoriented ion pairs is explicitly included.
Journal ArticleDOI
History of ferroelectricity 1938-1955
TL;DR: In this paper, a full understanding of the PHENOMENOLOGY of ROCHELLE SALT and POTASSIUM DIHYDROGEN PHOSPHATE is presented.
Journal ArticleDOI
The conical point in the ferroelectric six-vertex model
Dirk Jan Bukman,Joel D. Shore +1 more
TL;DR: In this article, the authors examined the behavior of the model in the vicinity of an unusual coexistence point that they call the "conical" point, which corresponds to additional singularities in the free energy that were not discussed in the original solution.
References
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Journal ArticleDOI
The Structure and Entropy of Ice and of Other Crystals with Some Randomness of Atomic Arrangement
Journal ArticleDOI
Eine neue seignette-elektrische Substanz
G. Busch,P. Scherrer +1 more
TL;DR: Wasps social and solitary, problems of ins t inct and intelligence, development and behavior, and notes on how to deal with these problems and more.
Journal ArticleDOI
Properties of Rochelle Salt
TL;DR: In a qualitative way, the anomalous properties of Rochelle salt can be explained on the basis of four different theories: ($a$) on the dipole theory, ($b$) by assuming polymorphic transitions at the Curie points, ($c) by postulating an anomalous piezoelectric effect, and ($d$) with an interaction theory which assumes that the structure and the fundamental properties of the crystal have no unusual characteristics as mentioned in this paper.