The temperature dependence of the long-wavelength optical phonons of $3C$-type SiC has been measured for temperatures up to 750 K. The LO-TO splitting diminishes with increasing temperature. From these data a weak decrease of the transverse effective charge with increasing temperature is also derived. The "explicit" temperature contribution to the variation of the transverse effective charge is determined experimentally and calculated in terms of a pseudopotential expression for the charge. Good agreement between theory and experiment is achieved.

• Received 28 August 1981

DOI:https://doi.org/10.1103/PhysRevB.25.3889