The dielectric properties and crystal structure of Ba0.85Sr0.15TiO3 and Ba0.85Sr0.15Ti0.92Zr0.08O3 ceramics were studied. The samples were synthesized by using solid-state method. The results show that the samples were single phase. The Ba0.85Sr0.15TiO3 exhibited tetragonal structure (space group P4mm), while with addition of 8 mol% Zr into Ba0.85Sr0.15TiO3 it shows that the sample exhibited orthorhombic structure (space group Amm2). The dielectric constant value increased from 1094 for pure, up to 4211 for Ba0.85Sr0.15Ti0.92Zr0.08O3 ceramic at Tc measured at 1 kHz. The Tc decreased from 80 °C down to 60 °C as 8 mol% Zr ions doped into Ba0.85Sr0.15TiO3 composition. The Ba0.85Sr0.15Ti0.92Zr0.08O3 ceramic exhibited lower dielectric loss, tan δ about 0.006 compared to Ba0.85Sr0.15TiO3 ceramic (tan δ = 0.009) when measured at 110 °C with frequency 1 kHz. The slope at low frequency region in capacitance vs frequency plot for both samples attributed by the grain boundary effect, whereas the high frequency plateau associated with the bulk response. The impedance spectroscopy analysis results show that both samples are dominated by the bulk response when an incomplete semicircle arc was observed in Zʺ vs Zʹ plot.

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Barium strontium titanate (BST), Ba0.8Sr0.2TiO3 ceramic prepared using conventional solid-state reaction method has achieved a single phase at 1400 °C. The Ba0.8Sr0.2TiO3 ceramic shows the highest dielectric constant and capacitance at 65°C about 4001 (10 Hz) and 2.92765 x10-9 F, respectively. The conductivity of Ba0.8Sr0.2TiO3 ceramic is in between the range of semi-insulator and insulator materials, and this composition also has exhibited the positive temperature coefficient resistivity (PTCR) properties jump of one order of magnitude from 2.06202 x 107 Ω.cm to 3.00958 x 108­ Ω.cm measured at 1 kHz.

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