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Journal ArticleDOI

Proton conductivity in pure and doped KH2PO4

01 Jun 1966-Journal of Physics and Chemistry of Solids (Pergamon)-Vol. 28, Iss: 2, pp 211-218
TL;DR: In this article, the electrical conductivity of pure and sulphate-doped KH2PO4 samples is analyzed in terms of defects likely to occur in KH 2PO4.
About: This article is published in Journal of Physics and Chemistry of Solids.The article was published on 1966-06-01. It has received 104 citations till now. The article focuses on the topics: Surface conductivity & Conductivity.
Citations
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Journal ArticleDOI
TL;DR: In this article, the authors show that Imidazole single crystal has a highly anisotropic conductivity; the ratio of conductivity in the c and a crystallographic directions is ∼103, and the limiting conduction process is possibly due to L−defect injection and transport back down the hydrogen bonded chain after the proton is discharged.
Abstract: Imidazole single crystal has a highly anisotropic conductivity; the ratio of conductivity in the c and a crystallographic directions is ∼103. In the c crystallographic direction, the hydrogen bonded direction, protonic carriers are discharged as hydrogen at the negative electrode. The limiting conduction process is possibly due to L‐defect injection and transport back down the hydrogen bonded chain after the proton is discharged. Conductivity in the a direction is probably electronic and extrinsic.

177 citations

Journal ArticleDOI
Kwang-Sei Lee1
TL;DR: In this article, it is suggested that the nomenclature high-temperature phase transition (HTPT) around T p should be replaced by that onset of partial polymerization at reaction sites distributed on the surface of solids.

131 citations

Journal ArticleDOI
TL;DR: The high temperature phase transition in KH2PO4 has been investigated by differential thermal analysis, thermogravimetric analysis, proton magnetic resonance and relaxation, infrared spectroscopy, and x-ray and quasielastic cold-neutron scattering as mentioned in this paper.
Abstract: The high‐temperature phase transition in KH2PO4 has been investigated by differential thermal analysis, thermogravimetric analysis, proton magnetic resonance and relaxation, infrared spectroscopy, and x‐ray and quasielastic cold‐neutron scattering. The transition is not connected with a static breaking up of the hydrogen‐bond network but rather with the onset of disordered hindered rotation of the H2PO4 groups around all three axes. It seems that rotation of H2PO4 groups is as well rate determining for the proton conductivity of this crystal.

91 citations

Journal ArticleDOI
TL;DR: In this article, the activation energy of migration is 1.02 eV in the temperature range between 150 and 179 eV and 2.94 eV at temperatures above 186 eV.

89 citations

Journal ArticleDOI
TL;DR: In this article, the occurrence of defects in solution grown KDPs was studied by means of X-ray transmission topography, and it was shown that the entrance of the M3+ impurities in the prismatic facets severely influences the perfection of pyramidal facets.

86 citations

References
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Journal ArticleDOI
TL;DR: 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.

521 citations

Journal ArticleDOI
TL;DR: In this paper, the authors reported the Infra-Red spectra of PO3−4, HPO2−4 and H2PO−4 ions in aqueous solution and in a number of crystalline salts.

348 citations

Journal ArticleDOI
TL;DR: In this article, the distribution of atomic nuclei in potassium dihydrogen phosphate at room temperature has been obtained by Fourier synthesis of single-crystal neutron diffraction data, and series termination effects have been examined and corrected for, either by specific assessment of the diffraction rings or by difference syntheses.
Abstract: Projections of the distribution of atomic nuclei in potassium dihydrogen phosphate at room temperature have been obtained by Fourier synthesis of single-crystal neutron diffraction data. Series termination effects have been examined and corrected for, either by specific assessment of the diffraction rings or by difference syntheses. The parameters so obtained are confirmed by least-squares analyses and give a reliability index of 7%. Hydrogen peaks occur midway between two oxygen atoms and appear circular when viewed along the O$\chembond{1,0} $H$\chembond{1,0} $O bond, but elliptical when viewed across it. The PO$_{4}$ tetrahedra are much more nearly regular than previously supposed, and the O$\chembond{1,0} $H$\chembond{1,0} $O bonds are inclined at not more than $\frac{1}{2}$ degrees to the xy-plane.

127 citations

Journal ArticleDOI
TL;DR: In this article, the authors measured the temperature dependence of the conductivity of single crystals of ammonium dihydrogen phosphate and proposed that activation for mobility in this solid is due to the simultaneous breaking of two hydrogen bonds independently.
Abstract: Measurements of the temperature dependence of the conductivity of single crystals of ammonium dihydrogen phosphate are described. Impurities introduced in known amounts as substituents in the lattice enable the activation energy for mobility to be separated from the total energy in the Boltzmann factor for conduction. With Ba++ as impurity, the activation energy is 10.1 kcal/mole, with SO4−− 10.9; the average, 10.5 kcal/mole, is taken to be the activation energy for mobility in this crystal. It ls proposed that activation for mobility in this solid is due to the simultaneous breaking of two hydrogen bonds independently. The σ0 factors, both for intrinsic conduction and for impurity conduction, agree reasonably well with the values expected from the theory of ionic conduction. Measurements on crystals enclosed in an evacuated space show that hydrogen gas is generated by the electrolysis of the crystal. According to Faraday's law the theoretical yield for a univalent ion leading to a diatomic molecule (H2) ...

62 citations