Microstructure and enhanced dielectric properties of BaTiO₃-SiO₂ nanocomposites using hydrogen treated nanoparticles

BaTiO₃ (BT) nanoparticles treated in H₂ and then coated with a layer of SiO₂ were used as the starting material to synthesise BT-SiO₂ nanocomposites through the conventional ceramic process. A denser morphology was obtained in the BT-SiO₂ composites. The H₂ treatment induced not only the oxygen vacancies, but also other changes (i.e. ionic disorders) in the BT. These ionic disorders were more permanent and enhanced the reaction between the BT and SiO₂ during the sintering process. Comparing with the nanocomposites sintered from the untreated BT nanoparticles, the nanocomposites sintered from the H₂ treated BT nanoparticles exhibit an enhanced dielectric performance (i.e. a higher dielectric constant and a high electric breakdown field). Among the temperatures (i.e. 850, 900, 950 and 1000°C) used to treat the BT nanoparticles in H₂, it is experimentally found that 950°C is the best. For example, for the composites with 20 wt% SiO₂, the dielectric constant is enhanced more than four times and the breakdown field is enhanced by about 30%. It is believed that the enhancement in the dielectric response is due to the dipoles formed by the ionic disorders, especially the acceptor defects.