Dielectric Materials for X9R Multilayer Ceramic Capacitors

Multilayer ceramic capacitors (MLCCs) have become important and are extensively used as passive components owing to their high performance, small size, and low cost. The characteristics of MLCCs necessary for applications in industrial devices include a large capacitance, low dielectric loss, and high breakdown strength. Recently, electronic instruments operating at high temperatures (>150 °C) have been extensively developed. Therefore, the temperature coefficient of capacitance ( TCC ) becomes an essential characteristic of MLCCs. Moreover, the X9R MLCC, which has a small TCC within ±15% at temperatures between −55 and 200 °C, has become more relevant for applications. The capacitive properties of the MLCCs depend on the dielectric characteristics of the ceramics used in their production. Hence, the development of dielectric materials with thermally stable dielectric properties is important for the fabrication of X9R MLCCs. BaTiO 3 (BT)- and K 1−x Na x NbO 3 (K 1−x N x N)-based materials have been explored for X9R MLCCs. This review introduces and systematically summarizes the dielectric characteristics of BT- and K 1−x N x N-based materials used in X9R MLCCs. Moreover, future research directions for these ceramics are suggested.