FERROELECTRIC PHASE-TRANSITION TEMPERATURES OF KTIOPO4, CRYSTALS GROWN FROM SELF-FLUXES

The origin of diversity in the reported ferroelectric phase transition (Curie) temperatures T-c, of KTiOPO4 (KTP) crystals grown from self-f luxes has been studied. A series of crystals has been grown by the top -seeded solution method from fluxes of different WP molar ratios and s olute concentrations, covering most of the KTP crystallization field i n the K2O-P2O5-TiO2 ternary system. Curie temperatures of as-grown and high-temperature annealed crystals have been measured using the stand ard dielectric technique and found to spread from 883 to 960 degrees C . We show that the actual T-c values depend on the solution chemical c omposition, and a functional representation of this dependence is give n. inherent gradients of the T-c in as-grown RTP crystals are discusse d in terms of the nonuniformity of their physical properties. (C) 1995 American Institute of Physics.