Design, fabrication and dielectric properties in core-double shell BaTiO3-based ceramics for MLCC application

BaTiO3-based ceramics with a core-double shell structure were fabricated by precipitation and the sol-gel method. Bi(Zn1/2Ti1/2)O-3-BaTiO3 (BZT-BT) or Nb oxide was chosen to be the shell-I (inner layer) or shell-II (outer layer) composition. The structure and dielectric properties were investigated by X-ray diffraction (XRD), HRTEM (High Resolution Transmission Electron Microscopy) and electron probe micro analysis (EPMA), with different core to shell ratio (n(c)/n(s)). Compared with the designed composition BT-Nb-( 0.2BZT-0.8BT), BT-(0.2BZT-0.8BT)-Nb was found to possess improved dielectric temperature stability, where the capacitance variation Delta C/C <= +/- 15% was achieved over a temperature range of -60-155 degrees C, with the dielectric constant and dielectric loss being in the order of 1860 and 0.011 at room temperature.