Effect of potassium and magnesium codoping on the dielectric properties of BST powders

Abstract

ABSTRACTK and Mg codoped BST powders were prepared by a sol-gel method, and the effect of doped concentration on the dielectric performances was studied. For comparison, pure, Mg doped and K doped BST powders were studied. XRD shows all powders reveal complete diffraction peaks and ABO3 cubic perovskite polycrystalline structures. Compared to the pure BST powder, Mg doped BST powder shows a little weaker crystallization, 5%∼15% K doped BST powders exhibit stronger crystallization, and the crystallization is getting stronger with increasing K doped concentrations from 2% to 15%. BST powder shows lattice parameter of 3.963 Å, Mg doping corresponds to 3.963 Å, 2%∼20% K doping correspond to 3.963 Å∼3.967 Å, and Mg and K codoping make lattice parameters increase from 3.967 Å to 3.974 Å. Mg2+ ion and K+ ion show acceptor doped mechanisms, Mg doping makes grains refine, and K doping makes grains grow. Pure BST powder and Mg doped BST powder show uniform grains with unclear grain boundaries, K doped BST powders can obtain uniform and dispersive grains with clear grain boundaries, but Mg and K codoping makes the uniformity and dispersity of the powders getting worse. Compared to pure BST powder, Mg doped BST powder shows smaller but more stable dielectric constant and dielectric loss, K doped powders tend to reveal larger and less stable dielectric constants and dielectric losses. Mg and K codoped BST powders show less than 35 dielectric constants, and lower than 0.02 dielectric losses. Dielectric properties are strongly dependent on the crystallization, doped mechanism and morphology. Mg doped and 2% Mg 2% K and 2% Mg 5% K codoped BST powders show low and stable dielectric constants and dielectric losses, thus can meet the requirements for tunable microwave applications and other applications.