Study on the Phase Transition of Lanthanide-Doped Titania Nanoparticles by Photoacoustic Spectroscopy

In this study, fairly uniform anatase TiO2 spheres doped with neodymium (III) have been prepared. It is found that the impregnation of neodymium (III) can remarkably inhibit the anatase–rutile transition. In order to analyze the correlation of the dopant effect with the local environment of neodymium (III) ions, photoacoustic spectra of the f–f transitions of neodymium (III) have been studied. The variation of the nephelauxetic parameters can be attributed to the substitutional neodymium (III) ions at low doping level (≤ 1 mol%), and to both the substitutional and interstitial neodymium (III) ions at high doping level (1 mol% to 8 mol%). The phase transformation mechanism of the samples has been interpreted based on the X-ray diffraction and transmission electron microscopy results. The nephelauxetic parameters are the same for all the samples calcined at 1150 °C. This is due to the segregation of neodymium (III) ions in the samples as a separated phase.