Synthesis of zirconia nanoparticles by sol-gel. Influence of acidity-basicity on the stability transformation, particle, and crystallite size

Abstract

Currently, zirconium oxide (ZrO2, also called zirconia) is used for restoration or as an implant in dentistry due to its properties and the aesthetics that can be achieved. In the present work, zirconia particles were obtained by the sol-gel method using acid or basic medium to study its influence on the nucleation and growth of the particle size and determine the crystallite size of the high-temperature phase. Also, to control the particle size and improve the solubility and dispersion of the colloidal particles resulting from the hydrolysis-condensation reactions, a mixture of alcohol of different chain lengths were used. The zirconia samples were heat treated at 400, 600, and 800 °C and up to 250 h of holding times to follow the growth of crystallite size of zirconia phases. The results showed tetragonal (ZrO2-t) and monoclinic (ZrO2-m) zirconia as predominant phases, regardless of the synthesis conditions and heat treatment used. The monoclinic phase is favored at elevated temperatures and prolonged holding times, while the tetragonal ones are favored at low temperatures. The holding time promotes the transformation from the tetragonal to the monoclinic phase in both media (acid and basic). However, this transformation is promoted by the basic catalyst, while the acid medium favors the stability of the tetragonal phase at 400 and 600 °C. The phase transformation, particle size, and crystallite size depend on the synthesis conditions and heat treatment used to obtain the zirconia particles.