コロイドプロセッシングにより作製したBaTiO_3の微構造と誘電特性

概要

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Density, grain size, and lattice parameters were measured on BaTiO_3 sintered in the temperature range from 800 to 1300℃ to study its dielectric properties. The powder compacts of ultrafine BaTiO_3 particles of 80 nm diarneter were formed by filtration of 2-methoxyethanol, 2 ethoxyethanol or methanol suspension and subsequent isostatic pressing to form a uniform micro structure of high density (58% of theoretical density). These green compacts were densified to relative densities of 96-99% at 1200 1300℃ within 2h. The c/a ratio of lattice pararneters approached 1 (pseudocubic) in BaTiO_3 with an average grain size of 0.5 μm owing to the large decrease in the c parameter with decreasing grain size from 2.3 to 0.5 μm. The dielectric constant (ε') at room temperature showed a maximum (ε' 〜6000) at an average grain size of 1.4 μm, which was obtained by sintering at 1200℃. The decrease in tetragonality in suburicrorneter sized grains reduced both ε' values below and above the Curie temperature, leading to the broadening of ε' in the wide temperature range of 18 to 220℃. The dielectric loss was smaller for higher density BaTiO_3 with larger grains.
社団法人日本セラミックス協会の論文
1994-12-01