Structure and properties of antimony-doped potassium titanyl phosphate single crystals

Antimony-doped potassium titanyl phosphate (KTP) crystals of the composition KTiOPO₄ are studied by X-ray diffraction analysis. It is shown that, with an increase of antimony content in KTP crystals, the occupancies of potassium positions change and new additional positions for potassium atoms arise. The formation of additional vacancies and splitting of the potassium-cation positions explain the considerable decrease in the temperature of the ferroelectric phase transition, enhancement of the relaxation phenomena, and an increase in electric conductivity of antimony-doped KTP crystals. Substitution of antimony atoms for titanium is accompanied by elongation of short and shortening of long Ti-O bonds in the TiO₆ octahedra, processes which result in lower intensity of second-harmonic generation in laser-irradiated KTP crystals.