Doping effect of rare-earth elements in BaTiO_3-R_2O_3-MgO dielectrics

The doping effect of rare-earth elements was systematically investigated in BaTiO_3- R_2O_3-MgO(R=La,Ce,Pr,Nd,Sin,Gd,Dy,Ho,Y,Er,Yb)dielectrics.SEM-EDS show that rare earth ions with small radius can form the core-shell-structured fine grains and the secondary phase R_2Ti_2O_7 appears because of the segregation of small ions on the grain boundary regions,while the large radius ones distribute uniformly in BT grains and promote grain-growth.The results indicate that the solubility of rare-earth ions in BaTiO_3 decrease as the ionic radius decreases.Due to the different site occupancy and compensation model,the small ionic radius R-doped ceramics show higher insulation resistivity compared with the large ionic radius R-doped ones.The large ionic radius R--doped samples exhibit single-peake-T,but the small ionic radius R-doped ones present double-peake-T and improve stability of△C/C-T meeting X8R code.