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A Raman scattering system devoted to high temperatures is presented. It is based on a pulsed system to remove thermal emission with retaining charge-coupled device (CCD) detection. Two types of optical gating are used: a Pockels switch or an intensified CCD (ICCD), combining in this case the optical gate and the CCD detection. The performances of both systems are presented and their respective advantages are discussed and compared. The ICCD device allows recording of spectra in the 2000 • C range, and typical results obtained on alumina and zirconia ceramics are shown.

The A1-symmetry Raman spectra of berlinite in a broad temperature range, encompassing the α–β phase transition, are reported. The temperature dependence of the lattice mode parameters is presented, particularly concerning the ‘soft’ mode at ∼220 cm−1, which exhibits a complex behaviour in the α phase. This is accounted for by coupling with another A1 mode and two-phonon background in the α phase. It is shown that the soft-mode parameters do not show appreciable discontinuities at the transition. The fact that four Raman active A1 modes instead of three are observed in the hexagonal β phase can be understood by assuming a dynamical disorder of Al and P atoms over trigonal α-phase sites.

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