Properties Of SrBi4Ti4O15 Ceramics Research Articles

Effect of increasing lanthanum substitution and the sintering procedures on the properties of SrBi4Ti4O15 ceramics

Lanthanum-substituted SrBi4Ti4O15 (SBTi) ceramic, that is SrBi4−x La x Ti4O15 (SBLTi), samples were calcined by solid-state reaction and densified using the microwave sintering and conventional sintering techniques. Their structural, morphological and mechanical properties were investigated. The microwave sintered samples showed high densities like 95% of the theoretical density with short duration exposures. Compared with SBTi ceramics and other lanthanide-substituted compositions, the incorporation of La 3+ results in clear improvement in properties for SBLT (x ∼0.75) with respect to the values of hardness and Young’s modulus of the microwave sintered samples (8.8–12.5 and 160–180 GPa) are higher than that for conventional sintered (8–10 and 135–155 GPa) samples.

Effect of Particle Size and Sintering Procedure on Microstructure, Dielectric, Ferroelectric and Mechanical Properties of SrBi4Ti4O15

Bismuth layered-perovskite compounds such as SrBi4Ti4O15 (SBTi) ceramics are prepared by solid state reaction. The SBTi ceramics are sintered by microwave and conventional sintering techniques. In this study, the effect of ball milling on different sintering processes, microstructure as well as on dielectric, ferroelectric and mechanical properties of SBTi ceramics is emphasized. The powder has been milled to produce nanocrystalline powders using a planetary ball mill. Different samples have been prepared by varying the milling time from 5 to 20 h, keeping the milling speed fixed at 300 rpm. The X-ray diffraction results show that crystalline powders with a single perovskite structure can be obtained when calcined at 700°C for 4 h. It has been observed that the average grain size, dielectric and ferroelectric properties are dependent on the duration of ball milling. The dielectric constant and loss tangent of the conventional sintered samples range between (140 and 165), and (0.05 and 0.07) respectively and those of the microwave sintered samples range between (155 and 175), and (0.04 and 0.06) respectively when measured at 1 MHz frequency. The microwave sintering process has been found to improve the homogeneity of the grains and morphology. The microwave sintering of the SBTi ceramics leads to higher densification (98% of the theoretical density), fine microstructure and good mechanical and ferroelectric properties in much shorter duration of time than that of conventional sintering process.

Effect of B-site equal-valent doping on ferroelectric properties of SrBi4Ti4O15 ceramics

The structures and properties of Zr and Hf-modified SrBi4Ti4O15（SBTi） ceramics were investigated. We find that the basic crystal structure is not changed after the substitution of equal-valent cations Zr4+ and Hf4+ for the Ti4+ ions at B site in SBTi. Compared with the higher-valent cation doping （V, Nb）, Zr4+ and Hf 4+ substitution can also improve the ferroelectric property of SBTi. The enhancement of remnant polarization （2Pr） by Hf4+ doping is obviously larger than that by Zr4+ doping, though these two cations have almost the same radius. This indicates that the reduced concentration of oxygen vacancy is not the only reason responsible for the improvement of the 2Pr in the B site doping, and other uncertain reasons should also be considered. The piezoelectric properties of these ceramics are investigated briefly. The tendency of piezoelectric constant changing with the doping dosage is nearly consistent with the tendency of 2Pr. Meanwhile, the dielectric properties of these ceramics are investigated, the Curie temperature of the samples varieds slightly with the doping amount, which implies that the good thermal stability of SBTi is not sacrificed.