High dielectric permittivity and low loss of SrBi₄Ti₄O₁₅ with PbO and V₂O₅ additions for RF and microwave applications

In this paper SrBi₄Ti₄O₁₅ (SBTi), a perovskite-type ceramic, with cation deficit A₅B₄O₁₅, was prepared by solid-state reaction method and PbO and V₂O₅ were added into SBTi (2, 5, 10 and 15 wt%). Samples were characterized through X-Ray Diffraction (XRD), Raman Spectroscopy and Scanning Electron Microscopy (SEM). Impedance Spectroscopy was carried out at room temperature. The analysis by XRD using the Rietveld refinement has confirmed the formation of single-phase compound with a crystalline tetragonal system (a = 3.8408 Å, b = 3.8408 Å and c = 41.0959 Å). A SEM shows globular grains (with addition of PbO) and crystal-shape ones (with additions of V₂O₅), from about 1 to 2 μm. The dielectric properties: dielectric permittivity (K′) and dielectric loss (tan δ) were measured at room temperature over a range of 100 Hz–40 MHz by complex impedance spectroscopy and in the microwave (MW) frequency region were studied. The study showed that these properties are strongly dependent on frequency and on the added level of the impurity. All the samples were analyzed taking into account to possible applications in radio frequency (RF) and MW devices.