Phase tuning of zirconia nanocrystals by varying the surfactant and alkaline mineralizer

The influence of cationic (CTAB)/neutral polymeric (PVP) surfactants and strong (NaOH)/weak (NH4OH) alkaline mineralizers on phase stabilization of zirconia nanocrystals synthesized by chemical precipitation is investigated. X-ray diffraction and micro-Raman analysis of the as-prepared samples show that tetragonal zirconia is predominant as compared to monoclinic using PVP with NH4OH. The phases are also evident from lattice fringes of TEM images and the corresponding SAED pattern. Photoluminescence spectra of samples reveal oxygen vacancies present in the zirconia nanocrystals. The group H Raman vibration modes identified are attributed to surface defects and quantum size effects of nanocrystals. The phase stabilization of zirconia nanocrystals is explained using the polymerization rate of tetramers during synthesis. The rate can be varied by proper selection of the surfactant and the mineralizer. A slow polymerization rate with PVP and NH4OH favors the formation of tetragonal zirconia. Thus, a simple method for phase stabilization of zirconia nanocrystals at room temperature using chemical precipitation by varying the surfactant and the mineralizer is demonstrated.