Papers by Keyword: BST Ceramic

Abstract: This research studied the effect of the different preparation technique on phase transition and electrical properties of Ba_0.8Sr_0.2TiO₃. The samples compared 3 preparation technique, there are conventional mix-oxide, molten-salt and seed-induced method. The samples prepared by molten-salt calcined at 800 °C, the samples prepared by conventional mix-oxide and seed-induced method was calcined at 1200 °C for 3 h. All of samples sintered at 1400 °C for 3 h. The phase formation and morphology of samples were characterized via X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The dielectric properties of the samples were measurement by LCR-meter.

Abstract: The dielectric properties of (1-x) Ba_0.65Sr_0.35TiO₃-xCaTiO₃(x=0, 0.03, 0.06, 0.10, 0.15) ceramics were investigated. XRD analysis shows that CaTiO₃ doping can be fully incorporated into the perovskite lattice of BST except increasing peak intensity. The experimental result shows that doping a certain amount of CaTiO₃ could form fine crystal grain structure, enhance the density, and enhance Ac withstand voltage strength, increase dielectric constant and decrease the dielectric loss. While doping excessive CaTiO₃ could make the geometrical distortion, increase the porosity and grain size, develop the internal stresses and finally lead to the dielectric constant decrease. The BSTC ceramics sintered at 1350 °C for 2 h with 6 mol.% CaTiO₃ doping has the best properties, ε_r of 3862, tanδ of 0.046, E_b of 5 kV/mm (AC), the value of C/C ranges is-26.7%~-66.2% in-50 °C ~ 100 °C temperature range.

Abstract: Ba₄Sm_9.33Ti₁₈O₅₄ (BST) ceramics were prepared by conventional solid-state reaction method. The effect of CuO-Bi₂O₃ co-doping on the sintering behavior and microwave dielectric properties of BST ceramics has been investigated. The results indicated that when the total addition of CuO-Bi₂O₃ doping agent was 1.0wt%, the sintering temperature of BST ceramics was reduced to 1240°C as a result of liquid-phase sintering effect derived from CuBi₂O₄. When the total addition of CuO-Bi₂O₃ was fixed at 1.0wt%, the microwave dielelctric properties of BST were improved by adjusting the mass percentage of Bi₂O₃. With the increase of Bi₂O₃ amount from 20wt% to 80wt%, the dielectric constant (ε_r) decreased, the quality factor (Q•f) increased and the temperature coefficient of resonant frequency (τ_f) shifted from negative value to positive value. The excellent microwave dielectric properties of ε_r=82.51, Q•f=7878GHz and τ_f=+6.02ppm/ were obtained for the sample with Bi₂O₃ amount of 80wt% when sintered at 1240°C for 3h.

Abstract: The effect of 9Bi2O3-CuO mixed oxides as sintering agent on sintering behaviors and dielectric properties of Ba0.6Sr0.4TiO3 (BST) ceramics were investigated. It was found that 9Bi2O3-CuO mixed oxides lowered the sintering temperature about 300°C and that highly denser BST ceramic pellets were obtained by sintering at 975oC with addition of 5.0-10.0wt% mixed oxides. For BST ceramics with 5.0wt% CB content sintered at 975°C, had a moderate dielectric constant (ε=1315), low dielectric loss (0.0067) and high tunability (36%) at dc electric field of 20kV/cm and at room temperature and at 10kHz.