The one‐phonon and two‐phonon Raman spectra have been measured in the temperature range 20–900 °C. The rate of decrease of the normalized frequencies with increase of temperature for the zone center, TO atLand TA atX, is 5.4×10−5/°C, while for TO atXand TA atLis lower, being 3.6×10−5/°C. We have also found that the relative intensity of Stokes and anti‐Stokes components of the &Ggr;‐point optical phonon deviates significantly from the value involving only the phonon occupation number, particularly at high temperatures. The decrease of the &Ggr;25′phonon from 521 cm−1at 20 °C to 493 cm−1at 900 °C should provide an unambiguous determination of the surface temperature due to laser heating.