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Microwave-assisted solid-state reactions (MSSR) are investigated for their ability to synthesize nanocrystalline BaTiO 3 powders at low temperatures. Ba(OH) 2 •H 2 O and TiO 2 •xH 2 O are, respectively, initial precursors for Ba and Ti. In this study, these precursors were mixed according to their chemical stoichiometry and heated in a temperature range of 100-1000 °C by MSSR. Nanocrystalline BaTiO 3 powders having an average size of 26 nm were produced by MSSR, even at 100 °C. The crystallization-related activation energy for the formation of BaTiO 3 with the precursors by MSSR was ~ 9.6 kJ/mol, which is less than 1/10 of the value (120 kJ/mol) when the conventional solid-state reaction was applied. The nanostructural and physical features of the MSSR-based powders are compared with those prepared using the conventional solid-state reaction.

The crystallization kinetics in BaTiO3 synthesis from hydrate precursors via microwave-assisted heating (MWH) were investigated. The structural and chemical features of powders synthesized via MWH and conventional heating (CH) were compared. The charged radicals generated under microwave irradiation were identified by chemical analysis and real-time charge flux measurements. Using Ba(OH)2∙H2O (BH1), Ba(OH)2 (BH0), and BaCO3 (BC) as the precursors for a Ba source, and TiO2∙4H2O (TH) for a Ti source, three different mixture samples, BH1TH (BH1 + TH), BH0TH (BH0 + TH), and BCTH (BC + TH), were heat-treated in the temperature range of 100–900 °C. BaTiO3 powders were synthesized at temperatures as low as 100 °C when sample BH1TH was subjected to MWH. Based on the growth exponent (n), the synthesis reactions were inferred to be diffusion-controlled processes (3 ≤ n ≤ 4) for MWH and interface-controlled processes (2 ≤ n ≤ 3) for CH. Current densities of approximately 0.073 and 0.022 mA/m2 were measured for samples BH1TH and BH0TH, respectively, indicating the generation of charged radicals by the interaction between the precursors and injected microwaves. The radicals were determined as OH− groups by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy.

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