Ferroelectric phase transition temperatures of KTiOPO4 crystals grown from self-fluxes

Abstract

The origin of diversity in the reported ferroelectric phase transition (Curie) temperatures Tc, of KTiOPO4 (KTP) crystals grown from self-fluxes has been studied. A series of crystals has been grown by the top-seeded solution method from fluxes of different K/P molar ratios and solute concentrations, covering most of the KTP crystallization field in the K2O–P2O5–TiO2 ternary system. Curie temperatures of as-grown and high-temperature annealed crystals have been measured using the standard dielectric technique and found to spread from 883 to 960 °C. We show that the actual Tc values depend on the solution chemical composition, and a functional representation of this dependence is given. Inherent gradients of the Tc in as-grown KTP crystals are discussed in terms of the nonuniformity of their physical properties.