Stable temperature dielectrics of (Ba,Ca)(Ti,Zr)O₃-based MLCCs with Non-core-shell structure by novel sintering approach

In this study, the high stability temperature coefficient of capacitance (TCC) characteristics of (Ba,Ca)(Ti,Zr)O₃-based multilayer ceramic capacitors (MLCCs) were investigated using a novel sintering approach that combines rapid heating and constrained sintering. The novel sintering approach is based on a sandwich structure that the constrained (Ba,Ca)(Ti,Zr)O₃-based MLCCs are covered with BaTiO₃ as a constraining layer on both sides. An in-plane tensile stress resulting from the mismatch between the constraining layer and the constrained layer during heating can effectively inhibit grain growth of (Ba,Ca)(Ti,Zr)O₃-based MLCCs and then modify the TCC characteristics of (Ba,Ca)(Ti,Zr)O₃-based MLCCs from Y5V (-82%蠆ΔC/C蠆 + 22% from -30°C to 85°C) to X5R (-15%蠆ΔC/C蠆 + 15% from -55°C to 85°C). The high continuity (>95%) of inner electrode and the fine grain size (0.56 μm) of BCTZ-based MLCCs with a non-core-shell structure can be attained by means of the rapid constrained sintering technique. The lifetime of the fine-grain-BCTZ-based MLCC fired by the novel sintering is superior to that of the coarse-grain-BCTZ-based MLCC fired by conventional sintering in a highly accelerated life test.