Effect of sintering temperatures on temperature coefficient of capacitance of KCa2Nb3O10 bulk-layered perovskite

• Published in: Journal of Asian Ceramic Societies Vol. ahead-of-print; no. ahead-of-print; pp. 1 - 11
• Main Authors: Kim, Jeong-Yeon, Hong, Gyo-Hee, Kim, Se Yun, Hwang, Seong-Mee, Shin, Weon Ho, Seo, Won-Seon, Kim, Sang-il, Kim, Hyun-Sik
• Format: Journal Article
• Language: English
• Published: Taylor & Francis 29.06.2023; Taylor & Francis Group
• Subjects: activation energy; KCa; KCa2Nb3O10; layered perovskite; sintering; temperature coefficient of capacitance
• ISSN: 2187-0764
• DOI: 10.1080/21870764.2023.2228090

Multilayer ceramic capacitors (MLCCs) for electric vehicles require their room temperature capacitance to change ≤ ±15% at −55°C to 200°C. The dielectric constant (ε) of BaTiO 3 , a dielectric material widely used in MLCCs, drops at >125°C making its application to electric vehicles difficult. Here, we propose KCa 2 Nb 3 O 10 (KCNO)-layered perovskite as a strong candidate for electric vehicle MLCCs as its ε does not change abruptly with temperature. The effect of sintering temperature on the temperature coefficient of capacitance (TCC) of KCNO is studied. The KCNO powder calcined at 900-1200°C is sintered at 1200°C-1300°C. Microstructure and temperature-dependent ε are determined by the sintering temperature, while the sintered density is related to the difference between the calcining and sintering temperatures. Only the room temperature ε of the samples sintered at 1300°C (except the one calcined at 900°C) varies ≤ ±15% at 25°C-200°C (ε ~250 at room temperature). The sample calcined at 1100°C and sintered at 1300°C has highly elongated grains and the highest activation energy. These factors are responsible for the TCC of the 1300°C sintered KCNO being ≤ ±15% at 25-200°C.