Microwave assisted citrate gel combustion synthesis of ZnO part-I: Assessment of structural features

Nanocrystalline ZnO containing Ag⁺, Al³⁺ and mixtures of (Ag⁺, Al³⁺) as dopants has been synthesized through a microwave assisted citrate gel decomposition technique. The study has two parts and in part-I, the process conditions for obtaining nanocrystalline ZnO have been investigated and the influence of pH upon microwave assisted gelation, interaction of microwaves with the precursor gels, evolution of structural features and ZnO particle morphology have been studied. Single phase ZnO has also been prepared to compare the effect of dopants. The analyses of the ZnO powders have been supported by XRD, TEM and SEM. The optimum is a gel precursor containing zinc nitrate and citric acid prepared in the molar ratio of 1: 2 and pH = 6.5, which results in nanocrystalline ZnO directly under microwave calcination at 950 W within 20 minutes. The TEM analysis confirms the ZnO particles have a size below 50 nm. The addition of dopant ions resulted in the formation of ZnO nano clusters. All these powders have also been studied for their photocatalytic and photoluminescence functional properties and the results are reported in part-II.