Cs₃W₃PO₁₃: A Tungsten Phosphate with One-Dimensional Zigzag Tunnels Exhibiting Strongly Anisotropic Thermal Expansion

A new tungsten phosphate, Cs₃W₃PO₁₃, is synthesized using the high-temperature flux method. Cs₃W₃PO₁₃ crystallizes in the space group Pnma and contains one-dimensional zigzag tunnels, which are found for the first time in tungsten phosphate. This highly anisotropic structural feature results in a very strong anisotropic thermal expansion, with thermal expansion coefficients of 14.15 ± 1.11 and 0.72 ± 0.22 M K^–1 along the a and b axes, respectively, over the temperature range from 13 to 270 K. In addition, thermal analysis, UV–vis–near-IR diffuse reflectance, and first-principles electronic structure calculations on Cs₃W₃PO₁₃ are performed.