Multiferroic features of fe-added BaTiO₃ ceramics prepared by microwave-assisted heat-treatment

The multiferroic features and secondary phases of Fe-added BaTiO₃ ceramics were investigated by examining two different types of BaTiO₃ nano-sized powders. Fe-doped powders were synthesized using a hydrothermal method, and Fe-coated powders were made using a sol-gel method. These powders were heat-treated by microwave sintering in a temperature range of 600-1200 °C. The ceramics made from powders coated with 40 wt% Fe exhibited a maximum saturated magnetization (Ms) of ~450 memu/g when they were heat-treated at 700 °C; the dielectric constant varied steadily from 200 to 1100 as the temperature was increased from 600 to 1200 °C. The formation of secondary phases such as BaFe₁₂O₁₉ and Ba₂Fe₂O₅ during heat-treatment seems to be critically associated with the observed evolution of ferromagnetic properties in the samples. The use of microwaves during heat-treatment resulted in lowering the preparation temperature by 200-300 °C, compared to conventional heating methods. The product of Ms and the dielectric constant exhibited its maximum value (239,200) for the BaTiO₃ ceramics prepared at 900 °C using microwave sintering.