SUBSTITUTION CHEMISTRY OF GALLIUM FOR TITANIUM IN NONLINEAR-OPTICAL KTIOPO4 - SYNTHESES AND SINGLE-CRYSTAL STRUCTURES OF KGAF1-DELTA(OH)(DELTA)PO4 (DELTA-APPROXIMATE-TO-0.3) AND KGA0.5GE0.5(F,OH)(0.5)O0.5PO4

The syntheses, single-crystal structures, and optical properties of KGaF1-delta(OH)(delta)PO4(delta approximate to 0.3) and KGa0.5Ge0.5(F,OH)(0.5)O0.5PO4, two structural analogues of potassium titanyl phosphate, KTiOPO4 (KTP), are described. Both phases crystallize in the typical noncentrosymmetric Pna2(1) space group adopted by KTP-type materials, but the powder second harmonic generation responses of KGaF1-delta(OH)(delta)PO4 and KGa0.5Ge0.5(F,OH)(0.5)O0.5PO4 are negligible compared to that of KTiOPO4. KGaF1-delta(OH)(delta)PO4 shows exclusive preferential substitution of fluoride ions into the octahedral-chain oxygen atom sites, and the resulting GaO4F2-delta(OH)(delta) octahedra do not show the typical octahedral distortion found in Ti-containing KTP phases. KGa0.5Ge0.5(F,OH)(0.5)O0.5PO4 shows no detectable Ga/Ge cation ordering, but an unusual, partial disordering of both the extraframework potassium cations occurs. Members of the KGaxTi1-x(F,OH)(x)O1-xPO4 solid solution series have been prepared as powders, and various trends across this series are reported. Crystal data: KGaF1-delta(OH)(delta)PO4: M(r) = similar to 222.79, orthorhombic, space group Pna2(1) (No. 33), a = 12.717(2) Angstrom, b = 6.3021(8) degrees, c = 10.431(2) Angstrom, V = 836(2) Angstrom(3), Z = 8, R(F) = 3.32% for 1479 observed reflections with I > 3 sigma(I). KGa0.5Ge0.5(F,OH)(0.5)O0.5PO4: M(r) = 222.73 orthorhombic space group Pna2(1) (No. 33), a = 12.756(2) Angstrom, b = 6.306(1) Angstrom, c = 10.413(2) Angstrom, V = 838(2) Angstrom(3), Z = 8, R(F) = 3.35% for 1332 observed reflections [I > 3 sigma(I)].