ScholarWorks@경상국립대학교

초록

In this study, we report a systematic investigation of the dielectric properties and structural evolution of K(Ca1 - xSrx)(2)Nb3O10 and H(Ca1 - xSrx)(2)Nb3O10 layered perovskite ceramics (x = 0, 0.25, 0.5, 0.75, 1) to evaluate their potential for high-temperature multilayer ceramic capacitor (MLCC) applications. While BaTiO3-based MLCCs suffer from dielectric instability above 120 degrees C, the proton-exchanged series H(Ca1 - xSrx)(2)Nb3O10 demonstrated stable temperature coefficient of capacitance (TCC) performance up to 200 degrees C, particularly for samples sintered at 1300 degrees C. Among them, HSr2Nb3O10 (x = 1) exhibited the highest dielectric constant (> 700 at 25 degrees C, 1 kHz) and exceptional TCC stability within +/- 15% across the full temperature range. Structural analysis revealed that sintering induces phase decomposition into stable binary niobates such as SrNb2O6 and Sr2Nb2O7. Interestingly, the dielectric constants of the sintered HSr2Nb3O10 ceramics exceeded the weighted average of their constituent phases. Transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) analyses revealed that strain fields and high-angle grain boundaries introduced during phase decomposition are responsible for this enhancement. In particular, the localized tensile stress at grain boundaries in HSr2Nb3O10 (x = 1) is suggested to promote high polarization regions, leading to improved dielectric performance. These findings highlight the role of strain engineering and multiphase interfaces in designing advanced dielectric ceramics for next-generation MLCCs.

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