FORMATION OF ZRO2 BY THE THERMAL-DECOMPOSITION OF ZIRCONIUM SALTS

Hydrated zirconium salts containing Cl-, NO3- or SO42- anions were the rmally treated up to 1300 degrees C. The thermal decomposition product s were investigated using the X-ray diffraction (XRD), Fourier transfo rm IR spectroscopy (FT-IR) and laser Raman spectroscopy. The thermal d ecomposition products of all three zirconium salts, characterized as a morphous material, showed a maximum of X-ray scattering at similar to 16 degrees and also in the corresponding FT-IR spectra a broad band at 450 cm(-1). With an increase of the heating temperature of all three salts (400 degrees C for ZrOCl2 . 8H(2)O, 400 degrees C for ZrO(NO3)(2 ) . 2H(2)O and 700 degrees C for Zr(SO4)(2) . 4H(2)O), the metastable t-ZrO2 was formed, which disappeared on further heating to higher temp eratures. The yield of t-ZrO2, measured by XRD, depended on the nature of the starting salt, and the highest value was obtained for ZrOCl2 . 8H(2)O salt. The t-ZrO2 phase formed from ZrOCl2 . 8H(2)O was thermal ly most unstable, while the presence of a small amount of t-ZrO2 was o bserved in the thermal decomposition product obtained by heating Zr(SO 4)(2) . 4H(2)O even at 1300 degrees C. Metastable tZrO(2), generated b y the thermal decomposition of ZrOCl2 . 8H(2)O or ZrO(NO3)(2) . 2H(2)O salt, was highly sensitive to mechanical treatment, while metastable t-ZrO2 formed from Zr(SO2)(2) . 4H(2)O was stable during the same proc ess. The nature of the starting salt influenced the formation of metas table t-ZrO2; however, when t-ZrO2 was once formed, its stability depe nded on the anionic impurities that remained in the oxide material.