Excellent thermal stability of dielectric properties of (1− x)(K_0.8Na_0.2)NbO₃–xBaTiO₃ ceramics for application in X9R multilayer ceramic capacitors

(1 −x)(K_0.8Na_0.2)NbO₃–xBaTiO₃ [(1 −x)(K_0.8N_0.2)N–xBT] ceramics are well densified at 1080 °C for 2 h. The Curie temperature (T_C) and orthorhombic–tetragonal phase transition temperature (T_O-T) of the ceramics considerably decrease and broaden with increasing x. Moreover, the ceramics (x ≥ 0.08) have large relaxor properties. The (1 −x)(K_0.8N_0.2)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)(K_1−yN_y)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 T_C and T_O-T. An MLCC is fabricated using the 0.9(K_0.8N_0.2)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(K_0.8N_0.2)N–0.1BT ceramic serves as a promising candidate for X9R MLCC devices.