The dielectric and flexoelectric properties of Mg2+/K+ doped BST films

Abstract

BST thin films have been prepared on Pt/Ti/SiO2/Si substrates by spin-coating. Different concentrations of K+ and Mg2+ have been doped in BST thin films by uni-doping and by binary alternate doping to improve the dielectric and flexoelectric properties of the films. At an annealing temperature of 800 °C, the doped thin film crystallizes well, and no heterogeneous phase is formed. The film surface is smooth and dense, and it has no cracks. The dielectric constant of undoped BST film is 262, the dielectric loss is 0.044, and the equivalent piezoelectric constant is 3.077 × 105 μC/N. When the K+ doping concentration is 7 mol%, the dielectric constant of the BST film is 446, the dielectric loss is 0.031, and the equivalent piezoelectric constant is 4.539 × 105 μC/N. When the doping amount of Mg2+ is 5 mol%, the dielectric constant of the film is 401, the dielectric loss is 0.025, and the equivalent piezoelectric constant is 4.165 × 105 μC/N. BST films with Mg2+/K+ alternate doping have better dielectric and flexoelectric properties than uni-doped films. The best doping conditions are 5 mol% Mg2+/7 mol% K+, with a dielectric constant of 479, a dielectric loss of 0.016, and an equivalent piezoelectric constant of 6.137 × 105 μC/N.