The Effect of (K_0.5Bi_0.5) Doping on Structural and Dielectric Properties of SrBi₂ Nb₂O₉ Ceramics

In this work, Sr_{1– x} (K_0.5Bi_0.5) _x Bi₂Nb₂O₉ solid solution powders were synthesized using a sucrose-assisted sol–gel combustion technique with x = 0, 0.3, 0.5, 0.7, and 1.0. Structural investigations of the compounds were conducted using X-ray diffraction (XRD) and transmission electron microscopy (TEM). AC dielectric measurements at a temperature range of 300–830 K were performed to investigate the effect and influence of (K_0.5Bi_0.5) substitution on dielectric properties. XRD results revealed that the increase of doping by (K_0.5Bi_0.5) caused a decrease in all lattice parameters, cell volume, and orthorhombic distortion, and an increase in orthorhombicity and crystallite size, which were discussed in view of the difference in ionic radii. TEM images showed agglomerated crystals with increasing (K_0.5Bi_0.5) dopant. The dielectric measurements revealed that the Curie temperature increased when Sr content decreased, which can be attributed to tolerance factors and structure distortion. On the other hand, dielectric loss was found to be reduced significantly, which can be attributed to the increase of complexity in form of distortion in the crystal structure. In addition, the dielectric loss plots of the samples revealed stable behavior through the temperature range between 300 and 650 K, which make these ceramics suitable for high-temperature applications.