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

Structure and dielectric behaviour of Sr-modified Bi4Si3O12 thin films prepared via sol gel method

Bismuth silicate (Bi4Si3O12, BSO) nanostructured films containing 0, 1, 2, and 3 mol% Sr were prepared via sol-gel method and annealed at different temperatures up to 700 °C. The effects of Sr content on the structure and morphology of prepared films were investigated. SEM images showed that surfaces of the prepared films were dense, smooth and homogeneous. The average particle size was changed from 30 to 35 nm as the annealing temperature was increased from 500 to 700 °C. Variation of the dielectric constant and dielectric loss as a function of frequency and annealing temperature for the synthesized thin films with different content of Sr were also studied. The dielectric constant and dielectric loss decrease with Sr addition, and reach the minimum for the sample containing 2 mol% Sr. These changes could be attributed to the crystal structure and formation of secondary phases