Slow Phase Transition and Macroscopic Size-Effect in CsZnPO 4 Crystal

Abstract

The three phase transitions at T 1, T 2 and T 3 in CsZnPO 4 crystal have been studied using an X-ray diffraction technique with both bulk and powder crystals. It is found in bulk crystals that all the three phase transitions take place and that two high temperature phase transitions at T 1 and T 2 are fast, while the lowest transition at T 3 is slow. It is found in powder crystals that the two phase transitions at T 1 and T 2 take place just as in bulk crystals, but the phase transition at T 3 does not take place and the phase III remains stable down to 10 K. This size-effect occurs in mm scale and should be called "macroscopic size-effect," as its origin may be quite different from that in nm scale. It is pointed out that the macroscopic size-effect may be closely connected with the slow phase transition.