Oxide based ceramics Ba _(1-x) Sr_xTiO₃ -BST are important for applications in electronics. Samples prepared by solid-state reaction from BaO, SrO and TiO₂ were sintered 1200-1260 ^oC for 2 hours. The following compositions were tested x = 0.25, 0.40, 0.35, 0.50, 0.60, 0.75, 0.90 and small amounts of 1 wt. % MgO and 1 wt. % MnO₂ were added to improve the grains crystallisation. Archimedes’s method for ceramic density measurements gives for x content the following values r(x) = 5.50–1.00 x, (g/cm³). XRD, EDAX, SEM methods were used for sample characterization. Perovskite structure, [1,2] was dominant and other minor phases were detected. Grains of ~5 mm size, well faceted, could be “seen” by SEM analysis for x = 0.75 samples. Pores and their dimensions grow for Sr content and sintering temperature increase. Dielectric permittivity and loss were investigated (1 kHz) and -150 to +150 ^oC temperature range at a pace of ~2 ^oC /min. Sharp transitions were noticed with the sintering temperature increase with some well defined peaks of permittivity of higher values (2000-4000). A shift of the Curie points to higher values was noticed with Sr content according to the eqn: Tc = 130 - 323·x, [3]. At room temperatures the permittivity measured at 1GHz show increasing values (1300 to 2500) with sintering temperature and decreased values of losses (2 % to less than 0.5 %). The x = 0.35 composition being in the ferroelectric phase could not be measured in microwave at room temperature. Our results points to important application of these BST compositions for microwave devices.

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