The nature of structural changes in nanocrystalline ZnO powders under linear heating conditions

The nature of exothermal and irreversible structural changes observed during linear heating of nanocrystalline ZnO powders was investigated using differential scanning calorimetry, X-ray, SEM and TEM analysis. Nanocrystalline ZnO powders were obtained by ultrasonic spray pyrolysis of 0.8 mol/dm3 zinc nitrate solution and subsequent decomposition of 2.7 μm sized droplets in the temperature range up to 600 °C, Fair=1.2 dm3/min. Produced particles are characterized by uniform and submicronic size, BET=4.94 m2/g, high phase purity and granular or circular “open” surface as the consequence of primary crystallites presence with average size of d=20 nm. The observed quasi nucleation-growth process during heating of this powder was discussed in the terms of primary crystallites structural changes.