Influence Of Thermal Treatment On The Formation Of Zirconia Nanostructured Powder Byt Hermal Decomposition Of Different Precursors

The paper presents some result concering the preparation of ziroconia powders starting from ZrOCl2 center dot 8H(2)O by using two synthesis methods: (a) precipitation with NH3, at 90 degrees C, and (b) thermal decomposition of carboxylate precursors, obtained in the reaction of zirconium nitrate and two different alcohols, 1,3-propanediol (PD) and poly(vinyl alcohol) (PVA), at 150 degrees C. The precursors obtained at different temperatures have been characterized by thermal analysis (TG, DTA) and FT-IR spectroscopy. DTA analysis evidenced very clearly the transition temperatures between zirconia crystalline phases. The precursors have been annealed at different temperatures in order to obtain zirconia powders and the as obtained powders have been characterized by means of X-Ray Diffraction (XRD). Fourier Transform Infrared Spectroscopy (FTIR). and Scanning Electron Microscopy (SEM). In case of precipitation method the presence of the tetragonal phase was observed at 400 degrees C, while the monoclinic phase appears a temperatures higher than 400 degrees C, becoming major crystalline phase starting with 700 degrees C. In case of the powders prepared by thermal decomposition of carboxylate precursors, the tetragonal phase was formed at temperatures below 700 degrees C, when the monoclinic phase begin to crystallize as secondary phase, in a higher proportion for the samples synthesized with 1,3-propanediol. All powders annealed at 1200 degrees C are pure monoclinic zirconia. SEM images have evidenced for the zirconia powders annealed at 1000 degrees C particles with diameters up to 150 nm, agglomerated in micrometer-sized aggregates, more individualized and homogenous than that obtained in the case of zirconia powder synthesized with poly(vinyl alcohol). (C) 2013 Elsevier B.V. All rights reserved.