Structural and dielectric properties of Bi-doped barium strontium titanate nanopowders synthesized by sol-gel method

Nano-crystalline barium strontium titanate, Ba0.5Sr0.5TiO3, (BST) powders were synthesized by sol-gel method, and the effects of Bi-doped on the microstructure and dielectric properties of BST powders were investigated. At first, the stable BST sols with optimum molar ratio were prepared and then different precents of bismuth were doped in precursor solutions. The samples, after drying and calcination at 850 °C for 2 h, were characterized by TG-DTA, FTIR, XRD, FESEM and LCR meter equipments. The results showed that the crystallite size and lattice parameter changed by increasing doped Bi content of BST. Also, with increasing Bi content from 2 to 4 mol%, average particle size of BSTB decreased from 40 to 35 nm. The dielectric constant for all samples increased with increasing calcination temperatures and then decreased after Curie temperature. An increase in the dielectric constant was observed up to a maximum of 1040 at a temperature of 80 °C for BSTB2 and 910 at 70 °C for BSTB4, approximately. The maximum value of dielectric constant and dielectric loss of the Bi-doped BST ceramics decreased with increasing Bi content.