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Solid solutions KTi1-XHfXOPO4 (х = 0.008 - 0.107) possessing the KTiOPO4 structure, have been synthesized in molten system K2O-P2O5-TiO2-HfF4. The crystal growth experiment of Hf-doped KTP crystal has been reported. The X-ray powder diffraction data and chemical analysis are also presented. It has been shown that KTiOPO4 crystal structure slightly changes when Hf incorporates into the framework. Transmission/absorption spectra of KTi0.974Hf0.026OPO4 crystals have been recorded. The incorporation of Hf ions shifts the optical absorption edge in the UV-visible spectrum towards the long-wavelength region with absorption near 387 nm. [ABSTRACT FROM AUTHOR]

The particularities of the chemical interaction in systems MIPO3 -MIIO(or Mn2O3)- MICl ( MI - Na, K; MII - Mg, Co, Ni, Zn) have been investigated at the temperature 1073 K and molar ratios P/ Mx = 1 or 2 and MICl/( MIPO3 + MIIO(or Mn2O3)) = 30. The conditions of formation of complex phosphates MІMIIPO4 and Na4Ni3(PO4)2P2O7 have been found. Influences of the nature of alkali and bivalent metals on the products composition were discussed. The advantages of chloride melts using (synthesis time reduction and temperature reducing) for preparing of complex phosphates were shown. The synthesized compounds have been characterized using the powder X-ray diffraction, Fourier transform infrared and diffuse reflectance spectroscopies. [ABSTRACT FROM AUTHOR]

The interaction in the molten system Rb2O-P2O5-TiO2-NiO was investigated at different molar ratios Rb/P = 0.5-1.3, fixed Ti/P = 0.15, Ti/Ni = 1.0 at temperature range 1073-953 K. The conditions of formation of complex phosphates RbTi2(PO4)3, Rb2Ni0.5Ti1.5(PO4)3 and RbNiPO4 have been determined. The new phosphate Rb2Ni0.5Ti1.5(PO4)3 (space group P213, a = 9.9386(2) Å) has been obtained and investigated by the single crystal X-ray diffraction and FTIR-spectroscopy. It has langbeinite-like structure, that is built up from mixed (Ni/Ti)O6-octahedra and РО4-tetrahedra. Rubidium atoms are located in closed cavities of 3D-framework. [ABSTRACT FROM AUTHOR]