Enhanced tunable dielectric properties of K and Mg co-doped Ba0.6Sr0.4TiO3 thin film

Barium strontium titanate (Ba _1 − x Sr _x TiO ₃ , BST) is well known mixed oxide exhibiting perovskite structure with tunable dielectric and ferroelectric properties, which vary based on the composition and temperature. In this study, Barium strontium titanate (Ba _0.6 Sr _0.4 TiO ₃ ), co-doped with donor dopant (K ⁺ ) and acceptor dopant (Mg ²⁺ ) has been prepared by sol-gel technique using a programmable spin coater on transparent ITO coated glass substrates. Influence of K (@5%)/Mg (@2%, 5%, 8%, 10%) co-doping has thereafter been investigated on the structural and dielectric properties of the films. Crystallite size of the samples has been noted to decrease from 33 nm to 24 nm with increasing Mg ²⁺ doping concentration, which is attributed to the substitution of Ti ⁴⁺ ions by smaller Mg ²⁺ ions. Also the tunability of the material is noted to reduce from 69–61% at a frequency of 1 kHz and 10V bias voltage and the same is ascribed to the reduced grain size of the material. However, the dielectric loss is observed to decrease with augmentation in Mg ²⁺ concentration which in turn leads to enhancement in the figure of merit (FOM) of the material from 101 to 290. From the results obtained in the current investigation K/Mg co-doping in BST can be perceived to be a promising way to optimize the dielectric properties of BST thin films for their potential application in microwave tunable device application.