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)O3-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 (nc/ns). 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 ΔC/C ≦ ±15% was achieved over a temperature range of −60–155 °C, with the dielectric constant and dielectric loss being in the order of 1860 and 0.011 at room temperature.