Variation of fundamental and higher-order Raman spectra of ZrO2 nanograinswith annealing temperature

ZrO2 nanograms annealed at different temperatures are systematically invest igated using x-ray diffraction (XRD) and Raman spectroscopy. Our results sh ow that bulk properties of nano-ZrO2 diminish but the defect-, surface-, an d size-related features display as grain size decreases. A critical size th at divides respective predominance is determined to be about 15 nm. Both XR D and Raman spectra of nano-ZrO2 of size above 15 nm are similar to bulk on es. On the contrary, those of nano-ZrO2 of size below 15 nm are deteriorate d bulk spectra with spectroscopic line broadening and merging, line intensi ty reducing, and position shifting. Deteriorated XRD spectra are essentiall y associated with increasing defects in small nanograins. General mode soft ening, a surface mode around 1040 cm(-1) and 14 weak second-order (overtone and combination) modes are characteristics of Raman spectra of nano-ZrO2 b elow 15 nn. They are associated with microstructure change of nanograins, i .e., they reflect the effects of grain size, surface, and the interaction b etween nanograins. [S0163-1829(99)02803-9].