New ceramic dielectrics for multilayer capacitors

Temperature stability of type II dielectrics can be improved by using and tailoring multiphase materials with core- shell microstructure. Using a mixture of Bi-layer-structure oxide and Pb-perovskites as shell forming phase a dielectric with X7D classification was obtained, showing permittivity 1550 at 1 kHz, loss 1 percent, relative C-variation within plus/minus 2,5 percent. The sintering temperature is 1120 centigrade. Advanced dielectric materials based on core-shell microstructure allow the fabrication of ceramic multilayer capacitors with stability in the intermediate range of COG and X7R and drastically reduced size compared to the COG type