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Hydrothermal Synthesis and Structural Characterization of (NH 4 )GaPO 4 F, KTP-type and (NH 4 ) 2 Ga 2 (PO 4 )(HPO 4 )F 3 , Pseudo-KTP-type Materials

2000; American Chemical Society; Volume: 12; Issue: 5 Linguagem: Inglês

10.1021/cm991177z

1520-5002

Thierry Loiseau, Capucine Paulet, Nathalie Simon, Vincent Munch, Françis Taulelle, Gérard Férey,

Zeolite Catalysis and Synthesis

Two new fluorinated gallium phosphates have been hydrothermally synthesized in the system GaOOH/H2O/H3PO4/HF/guanidine or NH4F (180 °C, autogenous pressure, 4 days). The structures of both compounds have been characterized by single-crystal X-ray diffraction. The (NH4)GaPO4F phase is isostructural with the KTiOPO4 (KTP) structural type. The structure of the second phase (NH4)2Ga2(PO4)(HPO4)F3, named pseudo-KTP or p-KTP, is closely related to that of KTP. In the latter, the existence of terminal P−OH and Ga−F bond along the b axis prevents the full connection by corner-sharing of the PO4 and Ga(O,F)6 units as it occurs in KTP structure. It results in a more distorted framework in which the occluded ammonium cations interact mainly with the P−OH and Ga−F terminal bonds. The structure of p-KTP was examined by 19F and 31P solid-state nuclear magnetic resonance spectroscopy using high-speed MAS experiments (30 kHz). 19F NMR indicates a full occupancy by fluorine for the atomic sites bridging the gallium atoms. Crystal data for (NH4)GaPO4F: orthorhombic, space group Pna21 (no. 33), a = 12.9207(2) Å, b = 6.440(1) Å, c = 10.4147(2) Å, V = 866.60(3) Å3, Z = 8, R1 = 0.0279%, wR2 = 0.0785 for 2216 reflections with I > 2σ(I). Crystal data for (NH4)2Ga2(PO4)(HPO4)F3: orthorhombic, space group Pna21 (no. 33), a = 12.4967(2) Å, b = 7.7015(1) Å, c = 9.8463(1) Å, V = 947.67(2) Å3, Z = 4, R1 = 0.0406, wR2 = 0.0985 for 2820 reflections with I > 2σ(I).