[en] Double magnesium zirconium orthophosphate Mg_0.5Zr₂(PO₄)₃ is synthesized by the sol-gel method. The compound prepared is characterized using electron probe microanalysis and X-ray diffraction. The crystal structure of the orthophosphate is refined by the Rietveld method in space group P2₁/n (Z = 4) at temperatures of 298 K [a = 12.4218(2) A, b = 8.9025(2) A, c = 8.8218(2) A, β = 90.466(1) deg.] and 1023 K [a = 12.4273(5) A, b = 8.9453(4) A, c = 8.8405(4) A, β = 90.320(3) deg.]. It is demonstrated that an increase in the temperature leads to an anisotropic expansion of the unit cell of the phosphate structure, but the structural type remains unchanged