Semiconductor/relaxor 0–3 type composites: A novel strategy for energy storage capacitors

We report a novel strategy to enhance the dielectric breakdown strength and the energy storage performance of lead-free relaxor ferroelectric ceramics through the fabrication of semiconductor/relaxor 0–3 type composites based on 0.6Ba(Zr0.2Ti0.8)O3-0.4(Ba0.7Ca0.3)TiO3 [BZCT] and ZnO. X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM) measurements confirm the formation of semiconductor/relaxor 0–3 type composites, in which ZnO particles are randomly distributed at the grain boundaries of BZCT. Further, the XRD analysis suggests a structural phase change from a tetragonal to a pseudocubic phase as the ZnO content increases from 0 to 5 wt. % in BZCT/ZnO composites. The pseudocubic phase favors the relaxor behavior of the composites as is evident from dielectric studies. The polarization-electric field (P-E) loops reveal the ferroelectric nature of the BZCT/ZnO composites. The energy storage properties of BZCT/ZnO composite ceramics as a function of different wt. % of ZnO are found to be optimum at 1 wt. % with a recoverable energy density of 2.61 J/cm3 and an efficiency of 74.2%, at an electric field of 282 kV/cm. Besides, an enhancement of 166% in the electric breakdown and 220% in the recoverable energy density was achieved compared to the BZCT ceramics due to the improved density and the large value of ΔP = Pm - Pr (25.55 μC/cm2). Therefore, this work evidences that the formation of the semiconductor/relaxor 0–3 type composites can be an effective way to significantly improve the energy storage performance of lead-free relaxor ferroelectric ceramics.