High-frequency dielectric characterization of novel lead-free ferroelectrics

摘要

Novel lead-free BFO-STO, BFO-CTO, and BFO-BZO ceramics were fabricated by the conventional method and their structural, microstructural, and dielectric properties were characterized. Dielectric measurements were carried out at room temperature in a large frequency range, from 20 Hz to 1.8 GHz. XRD analysis has demonstrated differences in the crystalline structure of the samples. BFO-STO exhibits a very different behavior compared to BFO-CTO and BFO-BZO ceramics because its XRD pattern contains peaks from diffracting planes of BFO and STO simultaneously. In comparison, the diffraction patterns of BFO-BZO and BFO-CTO are dominated by the peaks from diffracting planes of BZO and CTO, respectively. SEM observation has also revealed important differences in their microstructure. BFO-BZO and BFO-CTO have presented similar values of dielectric constant at low and high frequencies, ε' ~ 85 from 1 to 100 MHz. The lowest value of the loss tangent was measured on BFO-CTO with tan δ = 5 × 10~(-3) at f = 50 MHz. The BFO-STO ceramic has given higher values of the dielectric constant, closer to those reported for the bulk STO. Nearly frequency-independent high dielectric constant with very low loss over a broad frequency range (20 Hz to 1.8 GHz) of BFO-STO ceramic makes this material a potential candidate for high-temperature and high-frequency application with superior energy performance.