Excellent thermal stability of dielectric properties of (1− x)(K0.8Na0.2)NbO3–xBaTiO3 ceramics for application in X9R multilayer ceramic capacitors

(1−x)(K0.8Na0.2)NbO3–xBaTiO3 [(1−x)(K0.8N0.2)N–xBT] ceramics are well densified at 1080 °C for 2 h. The Curie temperature (TC) and orthorhombic–tetragonal phase transition temperature (TO-T) of the ceramics considerably decrease and broaden with increasing x. Moreover, the ceramics (x≥0.08) have large relaxor properties. The (1−x)(K0.8N0.2)N–xBT ceramics (0.09≤x≤0.11) exhibit excellent thermal stability of dielectric properties, satisfying the X9R multilayer ceramic capacitor (MLCC) specification requirements. However, the (1−x)(K1-yNy)N–xBT ceramics (0.0≤x≤0.3 and y = 0.5 and 0.8), which contain a large amount of Na+ ions, cannot satisfy the X9R MLCC specification requirements owing to the weakened relaxor properties and reduced decreasing rate of TC and TO-T. An MLCC is fabricated using the 0.9(K0.8N0.2)N–0.1BT ceramic. The MLCC complies with the X9R MLCC regulation requirements and has excellent stability of the applied electric field. Therefore, the 0.9(K0.8N0.2)N–0.1BT ceramic serves as a promising candidate for X9R MLCC devices.