Raman and Fourier-transform infrared photoacoustic spectra of granular ZnO2

Raman and Fourier-transform infrared photoacoustic spectra of nanometer-sized grains of monoclinic ZrO2 (5-80 nm) at room temperature are reported. A characteristic peak around 1040 cm(-1) is observed in the Raman spectra, which strengthens and shifts toward higher frequency with decrease of grain size. Its origin is attributed to a surface phonon mode of ZrO2. The other peaks observed in the Raman spectra shift toward lower frequencies and their bandwidths broaden when the grain size is decreased. A phonon confinement model is used to calculate the size dependencies of the position and bandwidth of peaks and the results show good agreement between theory and experiment. The Fourier-transform infrared photoacoustic spectra indicate that the intensities of the absorption peaks below 1000 cm(-1) decrease, while those above 1000 cm(-1) increase, and the positions of some peaks have redshifts with a decrease of grain size. The above phenomena are also related to the quantum size and surface effects of nanomaterials.