HIGH-TEMPERATURE PHASE-TRANSITION IN KH2PO4 CRYSTAL

DTA, weight loss, infrared and dielectric measurements have been performed on KH2PO4 (KDP) single crystal as well as on different particle size specimens. DTA result reveals two endothermic peaks. The lower peak at 180-degrees-C is particle size dependent and vanishes in specimen of particle size less-than-or-equal-to 0.1 mm. Dielectric measurements also show similar behaviour. No significant weight loss of the crystal was noticed when kept at 180-degrees-C. We are inclined to believe that fragmentation of crystal is likely to be responsible for the transition rather than PO4-group rotation or decomposition of KDP.