Thermoreactivity of Sol-Gel Precursor for ZnO-Based Thin Films

The thermoreactivity of a zinc acetate non-alkoxide solution used for the preparation of ZnO-based thin films was investigated in the temperature range 20-600ºC by TG-DTA, XRD and SEM data. We found that the formation in air of ZnO crystallites from the sol-gel precursor occurs above 150ºC simultaneously with the decomposition of an intermediary compound, most probably carbonate hydroxide (sclarite and/or hydrozincite). At 200 ºC, the crystalline structure is well defined in terms of ZnO hexagonal lattice parameters, although residual organic compounds and water were not yet fully removed and an amorphous phase coexists. A kinetic investigation on the thermal decomposition of sol-gel precursor from DTA data using Kissinger differential equation is also presented. Apparent activation energy values of about. 100 kJ mol-1 corresponding to the nonisothermal decomposition of solid precursors in the temperature range 170-250oC have been found.