Preparation And Property-research Of BiFeO₃ Ceramics And Thin Solid Films

Multiferroic material simultaneously shows ferroelectric order and ferromagnetic order, and performs Magnetic-Electric(ME) coupling effect, hence, has great application potential in many fields such as new data-storage materials, multifunctional devices, sensors, spin-electronic devices and so on. BiFeO₃(BFO) belongs to those few single-phase multiferroic materials who possess ferroelectricity and ferromagnetism at the same time at room temperature, thus gains more and more attention recently. In this paper, systematic study about series of BFO ceramic and thin film was carried out, just as follows:To overcome the difficulty of obtaining pure phase BFO samples, we compared several ceramic sintering method, finding that improved method of solid-state reaction did the greatest help to the phase formation of BFO ceramic, and that the optimal sintering temperature and time of target should be fixed to 850℃and 20min respectively. If bringing in doping ions, the sintering temperature should be increased. Meanwhile, we began to explore the thin film preparation process of RF-magnetron sputtering method, finally acquired the optimal process parameters, and produced high-quality, pure phase BFO thin film samples.Doping is deemed as one of the most effective ways to solve large leakage current brought by volatilization of Bi element and valence fluctuation of Fe3+ ions in BFO samples. Using the above-mentioned optimal process of sample preparation, we investigated the influence of A-site doping by Dy, B-site doping by Ti, and AB-site co-doping by Dy-Ti respectively on the improvement of BFO ceramics and thin films. The results seemed quite ideal.To study the influence of ion-doping on the microstructure and macroscopical performance of BFO ceramics and thin films, Pure and doped BFO samples with doping proportion ranged from 5% to 10%, 20% were compared, and the best doping proportion was picked out. For those Dy-doping samples(BDFO), when doping by 10%, both ceramic samples and thin film samples took on the best dielectric and ferroelectric properties. However, for those Ti-doping samples(BFTO), thin film displayed the most excellent characteristics when doping by 10%, while ceramic showed the best properties only when the proportion is 5%. For those Dy-Ti co-doping samples(BDFT), they behaved outstanding ferroelectric property, but comparatively poor dielectric property, especially in high frequency.