Alkali (alkaline-earth) metal, aluminum, and titanium complex orthophosphates: Synthesis and characterization

Phase formation in the A1 + xAlxTi2 − xP3O12 (A = Li, Na, K, Rb, or Cs; 0 ≤ x ≤ 2.0) and B0.5(l + x)AlxTi2 − xP3O12 (B = Mg, Ca, Sr, or Ba; 0 ≤ x ≤ 2.0) systems was studied using X-ray powder diffraction, electron probe microanalysis, and IR spectroscopy. The following double and triple orthophosphates were found to exist: A1 + xAlxTi2 − x(PO4)3 with A = Li (0 ≤ x ≤ 0.3), Na (0 ≤ x ≤ 1.0), K (x = 0, 1.0, or 2.0), Rb (x = 0, 1.0, or 2.0), or Cs (0 ≤ x ≤ 1.0) and B0.5(l + x)AlxTi2 − x(PO4)3 with B = Mg and Ba (x = 0), Ca and Sr (0 ≤ x ≤ 0.2). These orthophosphates crystallize in the structure types of kosnarite, langbeinite, cesium titanium arsenate, potassium aluminum phosphate, or rubidium aluminum phosphate. Their crystal parameters were calculated. For CsTi2(PO4)3 (x = 0), Rietveld refinement was carried out: space group Ia\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \bar 3 $$\end{document}d, Z = 32, a = 19.909(5) Å, V = 7892(1) Å3. This compound has a framework structure. The framework is built of TiO6 octahedra and PO4 tetrahedra; eight- and 12-coordinated Cs+ cations populate interstices.