Sol-gel synthesis of tetragonal ZrO2 nanoparticles stabilized by crystallite size and oxygen vacancies

In this letter, we present a facile route to produce metastable tetragonal zirconia (ZrO2) nanoparticles via pH-controlled precipitation of dilute zirconyl nitrate dihydrate [ZrO(NO3)(2)center dot 2H(2)O] solution in liquid NH3 under ambient conditions and calcination at 500 A degrees C for 2 h. The phase pure tetragonal ZrO2 nanoparticles are obtained at pH 9. The effect of pH on metastable phase stabilization in precipitated ZrO2 nanoparticles is demonstrated with the help of XRD, SEM/EDX, and X-ray photoelectron spectroscopy techniques. The stability of tetragonal ZrO2 phase is attributed to the smaller crystallite size and greater oxygen deficiency in phase-pure tetragonal ZrO2.