Tuning the optical, electrical and magnetic properties of Ba0.5Sr0.5TixM1−xO3 (BST) nanopowders

Abstract

Metal doped barium strontium titanate (BST; Ba_0.5Sr_0.5Ti_xM_1−xO₃) nanopowders have been successfully synthesized through the oxalate precursor route based on low cost starting materials. The effect of metal ion substitution, namely Fe³⁺, Mn²⁺, Co²⁺ and Y³⁺, on the crystal structure, microstructure and optical, electrical, dielectric and magnetic properties of BST was studied. The results revealed that a crystalline single cubic BST phase was formed for pure and Mn²⁺, Co²⁺ and Y³⁺ ion-substituted BST samples, whereas a tetragonal BST structure was obtained for the Fe³⁺ substituted BST sample at an annealing temperature of 1000 °C for 2 h. Furthermore, addition of the metal ions was found to decrease the crystallite size and unit cell volume of the produced BST phase. The microstructure of the produced pure BST phase was metal ion dependent. Most BST particles appeared as a cubic like structure. The transparency of BST was found to increase with metal substitution. Meanwhile, the band gap energy was increased from 3.4 eV for pure BST to 3.8, 4.1, 4.2 and 4.3 eV as the result of substitution by Fe³⁺, Mn²⁺ and Co²⁺ and Y³⁺ ions, respectively. The DC resistivity was metal ion dependent. The highest DC resistivity (ρ = 66.60 × 10⁵ Ω cm) was accomplished with the Mn²⁺ ion. Moreover, the addition of metal ions decreased the dielectric properties of the expected Mn²⁺ ion and increased the magnetic properties.