Single-Crystal Structures and Optical Properties of the Nonlinear Optical KTiOPO4-Type Materials K0.55Li0.45TiOPO4and K0.54Li0.46TiOAsO4Prepared by Molten Salt Ion-Exchange

Single crystals of the KTiOPO 4 (KTP) type phases K 0.55 Li 0.45 TiOPO 4 and K 0.54 Li 0.46 TiOAsO 4 have been prepared by molten salt ion-exchange reactions from their potassium-containing precursors. After ion-exchange, both phases maintain the distinctive distorted TiO 6 octahedra seen in KTiOPO 4 and KTiOAsO 4 . The pattern of lithium-ion substitution differs for these two phases: In K 0.55 Li 0.45 TiOPO 4, Li substitutes for both of the two crystallographically distinct potassium cations to roughly equal extent, whereas in K 0.54 Li 0.46 TiOAsO 4, the 9-coordinate K(2) atom is preferentially replaced by Li. The lithium cations occupy six-rings of TiO 6 and PO 4 polyhedra and adopt approximate square-planar coordination in both these materials. Second harmonic generation at 1064 nm is not significantly affected by lithium substitution in either of these phases. Crystal data: K 0.55 Li 0.45 TiOPO 4: M r = 183.55, orthorhombic, space group Pna 2 1 (No. 33), a = 12.741(2) Å, b = 6.357(1) Å, c = 10.535(2) Å, V = 853(2) Å 3, Z = 8, R ( F ) = 3.31% for 1393 reflections with I > 3σ( I ). K 0.54 Li 0.46 TiOAsO 4: M r = 227.11, orthorhombic, space group Pna 2 1 (No. 33), a = 13.018(2) Å, b = 6.589(1) Å, c = 10.766(2) Å, V = 923(2) Å 3, Z = 8, R ( F ) = 3.76% for 1637 reflections [ I > 3σ( I )].