Fabrication of Composite MLC's and Their Dielectric Properties

A new type of composite for multilayer ceramic capacitors (MLC's) was developed in order to improve the temperature dependence of capacitance. The new-type composites were composed of two kinds of dielectric layers laminated alternately, where both dielectric layers, L-layers and H-layers, were composed of lead-based relaxor materials with different Curie points of -30 to -40°C for L-layers and 100 to 120°C for H-layers. In the firing process of the composites, one-way diffusion occurred from H- to L-layers or in the opposite direction through the interfaces between H- and L-layers. The microstructure of the new composites was consequently inhomogeneous. The direction of one-way diffusion depended on the main components of L- and H-layers. The final compositions of L- and H-layers were selected to allow mutual diffusion between L- and H-layers. The temperature dependence of capacitance of the MLC's was less broad than the calculated curves which were derived from that of 2 kinds of ceramics with compositions of L- and H-layers. Composite MLC's with broad temperature dependence were finally formed by laminating the two materials alternately every 5 layers.