COMPOSITIONALLY INDUCED PHASE-TRANSITIONS AND NONLINEAR OPTIC RESPONSE IN ABCO(4) CRYSTAL SOLUTION PHASES ALIPO4 (A = SR, BA, PB)

Potentially useful second harmonic generating (SHG) compounds with the stoichiometry AxA'1-xLiPO4(A, A' = Sr, Ba, Pb) have been prepared. Th eir structural and optical properties are characterized by X-ray powde r diffraction, via/UV spectroscopy, SHG measurements, P-31 magic angle spinning (MAS) NMR, and Raman spectroscopy. BaLiPO4 isorthorhombic (o rtho I); a = 8.633(7) angstrom, b = 8.735(5) angstrom, and c = 5.211(4 ) angstrom. SrLiPO4 is hexagonal; a = b = 5.002(1) angstrom and c = 8. 209(2) angstrom. The regions of solid-solid solubility for these phase s upon mutual cation substitution are defined by XRD, SHG measurements , and P-31 MASNMR. P-31 isotropic chemical shifts are shown to be sens itive to cation distribution effects and to structural phase changes. P-31 MAS NMR spectroscopy also shows that for both pure BaLiPO4 and Sr LiPO4 there is only one crystallographically distinct phosphorus site. SHG intensities are maximized by bringing the solid-state solution ph ases close to structural phase transitions, with changes of more than an order of magnitude from the SHG responses of either of the pure pha ses.