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Effect of grain size on dielectric properties and reliability for ultra-thin MLCCs

BaTiO3-based ultra-thin (< 1 μm) multilayer ceramic capacitors (MLCCs) are fabricated with various grain sizes by sintering at different temperature under reduction atmosphere. Effects of the average crystal size on microstructure, tetragonality, dielectric performances, ferroelectric properties and reliability of MLCCs are studied via Raman spectrum, temperature coefficient of capacitance (TCC) curves, polarization-electric field (PE) loop and Weibull distribution of breakdown voltage (BDV). It is demonstrated that compared with coarse-grain sample, the fine-grain sample of 160 nm yields a higher TCC at the temperature range of-55~,85 °C (X5S, EIA, Electronic Industry Alliance), owing to the low defect contribution. Meanwhile, the fine-grain sample exhibits a smaller remnant polarization but a little higher saturated polarization due to its low tetragonality. According to Weibull distribution of BDV results, fine-grain ceramics possess high grain-boundary density, contributing to relatively high reliability.