Effect of Processing, Dopant and Microwave Sintering on the Dielectric Properties of BiFeO3 Ceramic

Abstract

BiFeO3 is of much importance for novel applications as sensors as well as actuators due to the coupling between magnetic and electric domains above room temperature and accepted high polarization in single crystal and thin film. Bulk BiFeO3 suffers from high impurity phase, poor sinterability and high dielectric loss and weak magnetism. The need of the hour is to prepare nanosize BiFeO3 powder with least amount of impurity phase that can be sintered to high density. Doping with suitable ion is required to improve the magnetic property of BiFeO3. In present work phase pure BiFeO3 is prepared by hydrothermal technique at 200oC. KOH concentration in solution controls the phase purity, powder morphology and particle size. Particle size was in the range of 15-20µm. Effect of polyvinyl alcohol as an additive to control the particle size was also studied. BiFeO3 and samarium doped BiFeO3 was also prepared by solid state method using nanosized Fe2O3 and Bi2O3. BiFeO3 with lowest impurity content can be prepared above 800oC. It is also found that samarium (Sm) doping in BiFeO3 significantly reduces the impurity content, grain size in sintered body and modifies crystal structure. With increase in Sm content, the phase purity was increased from 95% to 99%, upto 10% of Sm doping and then decreases for higher Sm content. The synthesized powder was sintered by conventional sintering and microwave sintering. Microwave sintering significantly reduces firing time but promotes grain growth. Microwave sintered sample has lower dielectric loss compared to conventional sintered BiFeO3.