The role of diffusion behavior on the formation and evolution of the core‐shell structure in BaTiO₃‐based ceramics

Abstract

In this work, the influence of starting particle size and sintering conditions on the microstructures and dielectric properties of BaTiO3‐based ceramics coated with 0.3Bi(Zn1/2Ti1/2)O3‐0.7BaTiO3 were investigated to reveal the core‐shell structure by using high resolution transmission electron microscopy technique coupled with energy‐dispersive spectrometer analysis. The ion‐diffusion behavior plays a critical role in the formation and evolution of the core‐shell structure and, therefore, significantly influences the dielectric properties. When using starting powders containing BaTiO3 particles larger than 100 nm in size and sintering for shorter dwelling times (0.5‐2.0 hours), a core‐shell structure could be formed and retained owing to the limited diffusion behavior, enabling BaTiO3‐based ceramics to meet the X8R specification for multilayer ceramic capacitors applications at high temperatures. However, when using 80 nm BaTiO3 nanopowders and further extending the dwelling time to 6.0 hours, more driving energy was provided to prompt ion diffusion, which led to the compositional inhomogeneity becoming homogenized.

Multifunctional barium titanate ceramics via chemical modification tuning phase structure

“…The BT‐based core‐shell structure consists of the compositional gradient regions with different properties, and the BT‐based nanoparticles are usually coated by insulating dielectrics (eg, SiO 2 , Al 2 O 3 , ZrO 2 , MgO). Then the diffused ε r ‐ T curves and improved BDS can be observed, which can significantly facilitate the dielectric temperature stability and boost the superior energy storage performance 216,217 . The introduction of porosity into ferroelectric ceramics can usually decrease the permittivity due to the ceramic‐air composite, which helps to optimize the performances of pyroelectric thermal detector, pyroelectric/piezoelectric energy harvesting, and piezoelectric acoustic sensors, etc 218‐220 .…”

Analyses of microstructure at degraded local area in Ni-multilayer ceramic capacitors under highly accelerated life test

“…The diffusion proceeds as the sintering temperature increases. 21,22) In this study, Dy could diffuse more in lot A than lot B, sintered at higher temperature.…”

“…9) Several studies have shown that suitable ion dopant in BaTiO 3 reduced mobile oxygen vacancies. 8,9) Various analysis techniques have been used for evaluation of core-shell structure, site occupancy of additive ions, and electric properties related to these microstructures, such as X-ray diffraction, [11][12][13][20][21][22] transmission electron microscope (TEM), 9,10,[21][22][23] differential scanning calorimetry, 12,13,21) thermally stimulated depolarization current, 8,9) I-V characteristics, 9,19) temperature coefficient of capacitance, 9,13,22,24) and impedance spectroscopy. [9][10][11]19,25) While the relationship between the average microstructures and the reliability has been investigated, our group has developed the technique to fabricate 'prebreakdown' MLCCs and to identify the degraded area without catastrophic changes, 26) for clear understanding of the degradation mechanism of MLCCs.…”

High‐entropy strategies boosting dielectric temperature stability in (Na0.4K0.1Bi0.5)TiO3 ceramics

“…In the quest to enhance the voltage and temperature stability of ceramic dielectrics, two commonly employed methods are the core-shell structure and the relaxation dispersion approach, illustrated in Figure 1B and C, respectively. The implementation of a core-shell structure aims to optimize dielectric temperature stability, 4,5 as depicted in Figure 1B. This structural configuration involves core and shell regions with distinct polarization levels, leading to separated dielectric peaks across the temperature range of interest.…”