Wideband dielectric spectroscopy of (Sr_0.7Bi_0.2)TiO₃ ceramics and its microscopic mechanism of polarization

Abstract

(Sr 0.7 Bi 0.2 )TiO 3 ceramics were fabricated by a solid state reaction, and a wideband dielectric spectrum was measured for understanding the microscopic polarization mechanism of (Sr 0.7 Bi 0.2 )TiO 3 ceramics. It was revealed that the dielectric permittivity of (Sr 0.7 Bi 0.2 )TiO 3 ceramics at 25°C was determined by dipole polarization as well as ionic polarization, whereas the permittivity of SrTiO 3 is mainly determined only by ionic polarization. The temperature dependence of permittivity suggested that (Sr 0.7 Bi 0.2 )TiO 3 ceramics belongs to ferroelectric relaxor, in which off-center Bi 3+ ions contribute to the formation of polar nanoregions (PNRs). The origin of the dipole polarization is considered the dipole fluctuations of PNRs. On the other hand, the ionic polarization of (Sr 0.7 Bi 0.2 )TiO 3 ceramics was suppressed by an influence of Sr-site vacancy, compared to that of SrTiO 3 . High permittivity of (Sr 0.7 Bi 0.2 )TiO 3 ceramics is mainly due to the dipole polarization associated with dipole fluctuation of PNRs.

Bi‐modified SrTiO3‐based ceramics for high‐temperature energy storage applications

“…The γ values for 0.9SBT‐0.1BMT/BMZ/BMH ceramics are 1.49, 1.49, and 1.60, respectively, showing high degree relaxor component, while the addition of Ti/Zr/Hf has minimal impact on the diffuseness. As shown in Figure A‐C, the T m of SBT‐based ceramics are around −50°C, being higher than that of pure SBT (around −100°C) . From room temperature to 200°C, the dielectric losses of all ceramics are less than 1% at 1 kHz, slightly increase with increasing frequency, being relevant to the relaxor component.…”

“…As shown in Figure 3A-C, the T m of SBT-based ceramics are around −50°C, being higher than that of pure SBT (around −100°C). 26 From room temperature to 200°C, the dielectric losses of all ceramics are less than 1% at 1 kHz, slightly increase with increasing frequency, being relevant to the relaxor component. The relatively low losses are very importance for thermal stability at high applied electric field, because the generated heat per unit volume is proportional to the dielectric loss, therefore the low dielectric loss is beneficial to the reduced heat generation and the possibility of the thermal breakdown.…”

Ultrahigh Energy Storage Properties in (Sr0.7Bi0.2)TiO3-Bi(Mg0.5Zr0.5)O3 Lead-Free Ceramics and Potential for High-Temperature Capacitors

“…Figure 3f gives the γ values of (1-x)SBT-xBMZ ceramics, being above 1.5, indicating relaxor characteristics. With increasing BMZ, the maximum permittivity (ε m ) at 1 kHz for ceramics with x up to 10% are similar, but the T m increases gradually from −68 • C to −27 • C, higher than the T m of (Sr 0.7 Bi 0.2 )TiO 3 ceramics which is around −100 • C [30]. The lower permittivity and higher dielectric loss for samples with x = 15% may be related to the secondary phase.…”

(Ba,Sr)TiO3–Bi(Mg,Hf)O3 Lead-Free Ceramic Capacitors with High Energy Density and Energy Efficiency

“…13−15 In addition, our recent study showed the grain sizes of 10 mol % Bi(Mg 0.5 Me 0.5 )O 3 (Me = Ti, Zr, and Hf, BMT/BMZ/BMH)-modified (Sr 0.7 Bi 0.2 )TiO 3 (SBT) ceramics were all below 1 μm, 16 being much smaller compared to undoped SBT ceramics with an average grain size of 5.6 μm. 17 The fine grain size is one of the reasons responsible for the high Weibull characteristic BDS of the above ceramics with values well above 400 kV/cm. 16 In addition to the dielectric constant and BDS, the dielectric loss is also important for energy storage capability of dielectrics, which is related to the hysteresis of the P−E loop.…”