Preparation And Properties Of Strontium Bismuth Niobate-based Bismuth Layer Structure Composite Ceramics

Bismuth layer-structured ferroelectrics(BLSF) as lead-free piezoelectric device are especially attractive technology, owing to their high Curie temperature, low dielectric constant and low aging rate, high breakdown voltage, high mechanical quality factor, the excellent stability of the resonance frequency, and the broad application prospects in the area of high temperature, high frequency, and information storage. However, it is difficult for the single bismuth layered materials to apply in industry. In this study, new type of bismuth layer/perovskite composite phase materials was synthesized via two-step synthesis to introduce perovskite phase N0.5Bi0.5Ti O3 to Sr Bi2Nb2O9. We analyzed the grain, component and composite process of the composite phase materials to reveal the relation between structure characteristics and electric properties, which is important to develop new materials used in the high temperature solid state sensors and detectors.(1–x)Sr Bi2Nb2O9–x Na0.5Bi0.5Ti O3(SBN–NBT, x=0.1, 0.2, 0.3, 0.4, 0.5) ceramics were prepared via a step ceramic processing. The crystal structure, microstructure and electrical properties were investigated. The coexisted structures of the bismuth layer structured phase and the perovskite Na0.5Bi0.5Ti O3 phase in the ceramics were determined by dielectric spectrum, analysis, X-ray diffraction, and scanning electron microscopy. The phase transition characteristics were investigated. The results show that two-layered SBN forms two-layered and three-layered BLSF inserted layer compounds, and subsequently form three-layered BLSF compounds. The structural, dielectric and piezoelectric properties depending on the NBT content were analyzed. The phase transition peaks shift to a high temperature area, the peak value ?r reduces and the dispersion degree of peak FHWM riess with the increasing of the NBT content. According to the dielectric response behaviors, normal ferroelectric–paraelectric phase transition to a relaxor-like behavior occurs when NBT content increases.When x=0.4 and γ=1.95, the sample shows the phase transition characteristics of typical relaxation ferroelectrics. As a result, optimized comprehensive electrical properties are obtained in the 0.9SBN–0.1NBT composition, i.e., TC=474 ℃, dielectric constant εr=177 and d33=13 p C/N.Basing on the composite ceramics synthesis process, we change the synthesis process of the SBN/NBT phase powders. The SBN/NBT powders were prepared via molten-salt and sol-gel method. And then SBN-NBT were fabricated by the step ceramic processing, as is used to investigate the effects of different powder synthesis process on the microstructures and dielectric properties of the SBN-NBT composite ceramics. The results showed that the coexistence structures of the bismuth layer structured phase and the perovskite phase have been determined using the molten-salt powers. The phase transition characteristics suggested an evolution from two-layered SBN to two-layered and three-layered BLSF inserted layer compounds when x=0.3. The single bismuth layer structured solid solution has been prepared using the sol-gel powers. With the increasing of the NBT content, phase transition peaks of composite ceramics shift to high temperature, the peak values ?r reduce and the dispersion degree of peak FHWM increase.In order to further develop bismuth layer structure lead-free piezoelectric ceramics with high performance, we used the superiority of the TGG and Composite Ceramics to fabricate the SBN-NKBT bismuth layer/perovskite powders by the nanoparticles NKBT modified on the surface of lamellae SBN via the hydrothermal method. Then, the SBN-NKBT(x=0.1, 0.3,0.4, 0.6, 0.8, SBN-NKBT) composite ceramics have been prepared via solid-phase sintering.The crystal structure, microstructure and electrical properties were systematically investigated.The coexistence structures of the bismuth layer structured phase and the perovskite phase have been determined in these ceramics using dielectric spectrum and X-ray diffraction,scanning electron microscope. The phase transition characteristics have been investigated and the results suggested an evolution from two-layered SBN to three-layered BLSF compounds and the disappearance of two-layered and three-layered BLSF inserted layer compounds.With the increasing of the NKBT content, phase transition peaks shift to high temperature, the peak values ?r reduce and the dispersion degree of peak FHWM increase. Dielectric response behaviors suggested an evolution from normal ferroelectric–paraelectric phase transition to a relaxor-like behavior with the increase of NBT content.