Effects of Mn doping and sintering condition on the microstructure, dielectric, and energy storage properties of Ba0.8Sr0.2TiO3 ceramics

Mn(2+)ion, as an acceptor dopant, is usually employed to optimize the microstructures and electrical properties of BaTiO3-based lead-free ceramic systems. In this work, Ba0.8Sr0.2(Ti1 -xMn(x))O-3 (BSTM, x = 0-0.005 mol) ceramics were synthesized using the solid-state sintering technique. The effects of Mn2+doping content and sintering condition on the microstructure, dielectric, and energy storage properties of BSTM ceramics were studied and discussed. Compared with undoped samples, the Mn doping with a low concentration of x \ 0.005 mol can effectively reduce the average grain size of BSTM ceramics when sintered at 1300 degrees C/3 h. It is also found that Mn2+ doping can decrease the dielectric loss and enhance remarkably the electrical strength (EBDS). This is because Mn replaces B-site Ti4+ ions, thus generating oxygen vacancies as well as defect dipoles 1/2Mn(Ti)(nn) -V-O(..)]. With an increase in Mn2+ doping content, more oxygen vacancies are produced to modify the microstructure and electrical properties. However, either elevated sintering temperature (e.g., 1325 degrees C) or prolonged sintering time (e.g., 1275 degrees C/5 h) can induce a rapid growth of grain size, leading to the weakened relaxation characteristics and the valence transformation from Mn2+ to Mn3+/ Mn4+, but the energy efficiency of BSTM ceramics is enhanced due to the thin P-E ferroelectric loops. The significant impacts of Mn2+ doping and sintering conditions on the morphology structure and electrical properties need to be considered for the better optimization of energy storage properties of relaxor ferroelectric ceramics.