Effects of amount of Ca on crystal structure, microstructure, ferroelectric properties, and dielectric properties of the CaxSr2-xBi4Ti5O18 (CSBTi-x) ferroelectric ceramics were investigated. The results show that single-phase layered perovskite ferroelectrics were obtained and no appreciable secondary phase was found.Ca-doping results in a notable enlargement of remnant polarization 2Pr. The 2Pr of CSBT-0.15 reaches a large value, the remnant polarization 2Pr and coercive field 2Ec were 18.1µC/cm2 and 120.2kV/cm, respectively. Dielectric constant and dielectric loss of CSBT-0.15 was also measured, showing dielectric constant εr=199~194 and dielectric loss tanδ=0.02~0.014 over the range of 100 kHz~1MHz, respectively.

Ca1-xSrxBi4Ti4O15 thin films were fabricated by sol-gel method on Pt(100)/Ti/SiO2/Si substrates. Influence of Sr content on the microstructure and ferroelectric properties of Ca1-xSrxBi4Ti4O15 thin films were systematically studied. The results indicate that Ca0.4Sr0.6Bi4Ti4O15 thin film has better ferroelectric properties with remanent polarization (2Pr) of 29.1+C/cm2, coercive field (2Ec) of 220 kV/cm. Furthermore, the film has good fatigue resistance. The better ferroelectric properties of Ca0.4Sr0.6Bi4Ti4O15 thin film originate from the relatively high concentration of a-axis oriented grains.

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The phase-separation and the crystallization of SiO2-MgO-Al2O3-K2O-Fe2O3-F glass were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe of microanalyzers (EPMA). The results reveal that the varieties and the morphology of crystalline phases formed depend sensitively on the thermal treatment schedules. During the isothermal treatments, the crystalline phases of mica, mica and iron oxide (FeFeO4), and FeFeO4 as major crystals are precipitated in the glass samples heat-treated at 900, 1000 and 1050°C respectively. However, the two-step heat treatment beginning at 900°C for 1h and subsequently followed at 1050°C for 1h leads to the precipitation of mica crystal and no any signs of FeFeO4 crystalline phase is observed. Also the morphology of sample is different from that of the isothermally treated glass at 1050°C, but is similar from that of sample at 900°C. A “worm”-shaped phase-separation is observed in the sample heated at 800°C for 0.5h, which exhibits different morphology from that of droplet- or globule-shape conventionally discerned. EPMA results show that the incorporation of Fe2O3 accelerates accumulation of fluorine element, promoting the phase-separation and the crystallization of the present glass.

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