Synthesis, characterization and dielectric properties of xBaTi4O9–(1 − x)BaSm2Ti4O12

Abstract

Temperature stable microwave dielectric materials xBaTi4O9–(1 − x)BaSm2Ti4O12 were produced through a conventional solid-state reaction procedure in the work. The structural and microwave dielectric properties of the ceramics were determined with the purpose of finding a microwave ceramics with high dielectric constant (er), high quality factor (Q × f) and zero temperature coefficient of resonant frequency (τf). Experimental results showed that BaTi4O9 additions affected grain growth and densification, the grain size distribution, and tuned the dielectric properties of the produced ceramics. The amount of BaTi4O9 strongly influenced the densification and the microstructure (i.e. grain shape and size) of the produced ceramics. Analysis of the experimental results suggests that the microstructural features can be correlated to the dielectric properties of these ceramics. Accordingly, the dielectric constant (er) and the temperature coefficient of resonant frequency (τf) of the produced BaSm2Ti4O12 ceramics can be tuned with the amount of BaTi4O9 additions and the sintering process parameters. The best dielectric properties were achieved for BaSm2Ti4O12 ceramics with 15% BaTi4O9 (er = 66, Q×f = 15,730 GHz and τf ≈ 0 ppm/°C). Experimental results suggest that BaTi4O9 doping improves the dielectric properties of the sintered BaSm2Ti4O12 perovskite ceramics, which are further enhanced by doping with BaTi4O9 in small amounts. However, further increase of BaTi4O9 content jeopardizes them.