[en] The pressure dependence of the phonon frequencies in the isomorphic materials ZrO₂ and HfO₂, and the temperature dependence of the phonon frequencies of HfO₂, were investigated by Raman spectroscopy in the ranges 0 to 16 GPa and 20 to 800 K. The comparison of the pressure dependence of the Raman spectra of the two materials helps to elucidate the correlation of their vibrations in the intermediate spectral region A(240 to 410 cm^-1). The high-pressure phase of ZrO₂ is stable up to 16 GPa and of tetragonal symmetry. HfO₂ does not show any pressure-induced phase transition up to 12 GPa, while the temperature effect on the phonon frequencies is similar to that of ZrO₂