The lattice parameters of SrLaGaO 4 (SLG) single crystal were measured in the temperature range from 300 to 700 K using X-ray spectroscopy. The measurements revealed that (i) the thermal coefficient along a and c axes is different and (ii) thermal expansion coefficient in a direction depends on temperature, showing the transition temperature at about 460 K. To verify this result we have also studied the Raman intensity I R and full width at half maximum (FWHM) of the Raman band at 218 cm - 1 ascribed to the librational lattice mode. The above temperature dependences display a characteristic discontinuity at about 460K which coincides with the previous data obtained from X-ray measurements. The obtained results are discussed in terms of the nature of defects which might arise in the ABCO 4 lattice during the crystal growth process.