Structure and properties of niobium-doped potassium titanyl phosphate crystals

A series of potassium titanyl phosphate crystals, KTiOPO4, with various con centrations of niobium dopant has been grown, and some of their physical pr operties and structural characteristics have been studied. The incorporatio n of a small amount of niobium results in considerable changes in the elect rical conductivity of KTP : Nb crystals and the temperature of the ferroele ctric phase transition. Thus, the presence of 3-4 at. % of niobium results in an increase of conductivity by more than an order of magnitude, whereas Te decreases from 930 to 620 degrees C. The X-ray diffraction study of the crystals has been performed at room temperature; the neutron diffraction an alysis was made at temperatures of 20, 330, and 730 degrees C, It was revea led that two crystallographically independent positions are statistically ( by 90%) occupied by potassium cations, which results in the concentration o f potassium atoms in the structure higher than it was expected from the con dition of preservation of crystal electroneutrality. At high niobium concen trations, the monoclinic compound of the composition K2TiNb2P2O3 is formed. (C) 2000 MAIK "Nauka/Interperiodica".