Influence of Alkaline Mineralizer on Structural and Optical Properties of ZrO₂ Nanoparticles

In this work, the influence of different alkaline mineralizers on structural and optical properties of zirconia nanoparticles synthesized by chemical co-precipitation technique using zirconium oxychloride octahydrate (ZrOCl₂·8H₂O) as precursor is studied. The mineralizers used for the synthesis of nanoparticles are NaOH and NH₄OH. X-ray diffraction, Fourier Transform Infrared (FTIR) spectroscopy, UV-visible absorption spectroscopy and Photoluminescence (PL) spectroscopy were used for characterizing the nanoparticles. Structural analysis of the sample synthesized using NaOH shows monoclinic phase as predominant one, however when NH₄OH is used the major phases are cubic and tetragonal. The difference is attributed to the number of hydroxyl ions produced and their rate of release during the reaction process. The presence of these phases in both samples is further confirmed by vibrational bands of FT-IR spectra. Also, the low energy bands due to the presence of defects in nanoparticles are also explicitly observed in the photoluminescence spectra. Further the defects lead to a red shift in the band gap of ZrO₂ which is observed when the samples are subjected to UV-absorption spectroscopy analysis. It has been demonstrated that zirconia nanoparticles with desired structural properties can be synthesized by changing the type of mineralizer without the necessity of doping.