Effect of PbO-B2O3-BaO-SiO2 glass additive on dielectric properties of Ba0.5Sr0.5TiO3 ceramics for radio-frequency applications

In this work, the effects of PbO-B2O3-BaO-SiO2 (PBBS) glass addition (in increasing wt%) into Ba0.5Sr0.5TiO3 (BST0) ceramic on sintering, phase, and dielectric properties of BST0 are studied. The Ba0.5Sr0.5TiO3 (BST0) ceramic was synthesized by the conventional solid-state reaction method, and the PbO-B2O3-BaO-SiO2(PBBS) glass was formed by melting and quenching process. The PBBS glass with different weight percentages (3, 5, 8 and 10 wt%)is added to BST0 ceramic (BST3, BST5, BST8, and BST10, respectively) as a sintering aid to reduce the sintering temperature. Addition of glass helps in better sintering at lower temperatures with the presence of liquid phase at the respective sintering temperatures. The results of liquid phase-sintered ceramics are compared with the BST0 ceramic sintered at 1523 K. The BST10 with 10 wt% glass showed the lowest sintering temperature of 1148 K. Rietveld refinement analysis of BST0 ceramic confirmed the formation of single phase with cubic crystal structure. X-ray diffraction patterns of all liquid phase-sintered ceramics showed that the glass has minimal reaction with the BST0 ceramic and does not affect the crystal structure. Dielectric characterization was performed within the temperature range 20-450 K and frequency range 1 kHz to 1 MHz. It is revealed that the transition temperature shifted with different weight percentage of glass addition. All the compositions exhibit the paraelectric phase at room temperature. Dielectric properties were also measured in the microwave frequency range 8.5-11 GHz at room temperature. BST10 shows the stable and highest dielectric constant (average value of epsilon(r) = 27) with lowest dielectric loss (tan delta = similar to 0.121). Fourier transform infrared (FTIR) and Raman spectroscopy confirmed the formation of desired compositions by detecting molecular vibrations and chemical bonding. The synthesized ceramic is a low-cost candidate and can have potential uses in the radio-frequency applications.