An Nb-doped analogue of KTiOPO4; Structural and nonlinear optical properties

The growth, crystal structure and powder second-harmonic generation (SHG) of crystals of K0.84(Ti0.92, Nb0.08)OPO4 (KTNP) is reported. The crystal structure of KTNP, orthorhombic, space group Pna21 (C92v), a=12.815(4), b=6.413(2) and c=10.597 Å, has been refined to R=0.034. The incorporation of 8% Nb mostly on the Ti(1) site is shown to be self-compensated electrically by the creation of vacancies on the K+ sites. The powder SHG from a KTNP sample has been measured and compared with that from a similar stoichiometric KTiOPO4 sample. The results are discussed with reference to the small differences between the crystal structures of KTNP and KTP.