Some temperature dependent properties of potassium dihydrogen phosphate
Single crystals of potassium dihydrogen phosphate (KDP) have been grown at room temperature from saturated aqueous solutions. The thermal behaviour has been studied by differential thermal analysis and confirmed by X-ray diffraction and infrared spectroscopy. When heated to 613 K, KDP loses its water content and a transition takes place from the tetragonal orthophase to the monoclinic meta-phase. The resistivity of KDP crystals has been found to decrease exponentially with temperature over the temperature range of 293 K to 383 K above which it attains a constant value independent of further temperature rises up to 478 K. A value of 0.588 eV has been estimated for the activation energy of rotation of the phosphate group which controls conduction over the temperature dependent region of the resistivity curve. Glow curves of gamma-ray irradiated single crystals subsume peaks similar to those detected for the polycrystalline powder. Energy depths varying from 0.20 eV to 0.46 eV have been calculated for the various trapping states created by gamma irradiation. Effects of increasing gamma dose have been studied and found to cause an increase in number and intensity of the glow peaks. Slight shifts in peak temperatures to lower values are also noted at high gamma doses and attributed to the combined effect of dose rate and interactions between trapping centres.
KeywordsDifferential Thermal Analysis Glow Curve Gamma Dose Resistivity Curve Potassium Dihydrogen Phosphate
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