Processing of BiFeO3 Ceramics by Gelcasting

Abstract

An attempt has been made in preparing BiFeO3 articles based on gel casting system. For this purpose, BiFeO3 was synthesized by glycine-nitrate auto combustion route. The powders were calcined between 450-550oC with different soaking time. Phase pure BiFeO3 was obtained at 550oC with a soaking time of 2 hours. Phase purity was authenticated by X- ray diffraction technique. Employing BET 5 point method, surface area was measured. The surface area calculated is about 10.36m2/g which is suitable for powder dispersion in gel casting system. Then the phase pure powder was used in gelcasting based on Acrylamide (AM) - N,N/-methylene bisacrylamide (MBAM) premix solution. First, the ratio of AM-MBAM was optimized. Then, stable dispersion of BiFeO3 in that premix solution was also achieved with Triammonium citrate (TAC) as dispersing agent with pH ~9. Then the slurry was gelcasted in humid atmosphere between 50-60oC. The gelcasted bodies have good green strength and free of surface exfoliation defect. Differential scanning calorimetry was employed to study the thermal behavior of green bodies. Gelcasted bodies were first machined in green state and sintered at different temperature between 750-825oC to obtain the final product. The density of gelcasted body was measured and phases are again identified using X-ray diffraction. It has been observed that with increase in sintering temperature from 750 to 800oC theoretical density increased from 92.5% to 94%. A small amount of impurity was also present in sintered product.