Dopant influence on BST ferroelectric solid solutions family

Solid solutions of the Ba1−xSrxTiO3 (BST) type are very attractive for applications in information technology, but also in microwaves for such electrically controlled devices as phase shifters, tunable filters, steerable antennas, varactors, etc. A family of solid solutions with x = 25, 50, 75, 90% was prepared by standard powder technology-solid state reaction and sintered at 1230 °C and 1260 °C. Dielectric permittivity and loss at low (1 kHz) and high frequency (1 ÷ 2 GHz) were measured on a large temperature range − 200 °C ÷ + 200 °C. The influence of Sr content and of 1 wt.% MgO and 1 wt.% MnO2 doping on the complex dielectric constant was studied. The dielectric permittivity at high frequencies and room temperature considerably decreases with the increase of Sr content. Similarly, low frequency measurements showed a severe and almost linear decrease of the Curie Point with the increase of Sr fraction. At low Sr content, the measured ceramic densities slowly decrease with Sr fraction and represent about 92% of the X-ray density ρ(g/cm3) ≈ 5.99-0.99·x. At x = 90% Sr concentration, very low-density ceramics were obtained with both sintering temperatures.