The ordered Ca3TaGa3Si2O14and disordered La3Ga5SiO14crystals of the lantangallium silicate family were grown via the Czochralski method. The independent coefficients of thermal expansion of crystalsαcandαawere determined using X-ray powder diffraction based on the analysis of X-ray diffraction spectra measured in the temperature range of 25~1000 °C. It is shown that, in the temperature range of 25~800 °C, the thermal expansion coefficients are linear. At temperatures above 800 °C, there is a nonlinear character of the thermal expansion coefficients, associated with a decrease in the Ga content in the crystal lattice.