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-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 K ₂O-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 T_c values depend on the solution chemical composition, and a functional representation of this dependence is given. Inherent gradients of the T_c in as-grown KTP crystals are discussed in terms of the nonuniformity of their physical properties.