Non-aqueous dispersion properties of pure barium titanate for tape casting |
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| Institution: | 1. Nanotechnology Research Laboratory, Desh Bhagat University, Mandi Govindgarh 147330, Punjab, India;2. Magnetics & Advanced ceramics laboratory, Department of Physics, Indian Institute of Technology, Delhi 110016, India;3. School of Physics & Materials Science, Thapar University, Patiala 147004, Punjab, India;1. Faculty of Physics, Vilnius University, Vilnius, LT-10222, Lithuania;2. Institute of Solid State Physics, University of Latvia, Riga, LV-1063, Latvia;1. Department of Electronic Engineering, East China Normal University, Shanghai 200241, China;2. Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050, China;1. Department of Chemistry, Faculty of Science, Kumamoto University, Kumamoto 860-8555, Japan;2. Department of Chemistry, Chiba Institute of Technology, Shibazono 2-1-1, Narashino, Chiba 275-0023, Japan;3. Faculty of Chemistry, University of Wroclaw, 14, F. Joliot-Curie, 50-383 Wroclaw, Poland |
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| Abstract: | The dispersion properties of concentrated (25.0 and 50.0 vol.%) dispersions of high purity barium titanate powder dispersed in a methyl ethyl ketone (MEK) -ethanol solvent of moderate dielectric constant were studied in an effort to improve the uniformity of tape cast and sintered bodies. An amphoteric phosphate ester surfactant was found to be an effective dispersant. The dispersion properties of the phosphate ester were subsequently investigated by rheological, adsorption, conductivity, and electrophoretic mobility methods in order to evaluate a dispersion mechanism.Optimum dispersion occurred at an azeotrope solution of MEK and ethanol. The barium titanate particles dispersed in dry solvents exhibited a greater degree of dispersion than particles dispersed in hydrated solvents. The adsorption isotherm for the adsorption of the phosphate ester onto barium titanate particle surfaces using dry solvents exhibited a well-defined plateau corresponding to monolayer surface coverage. The plateau was less well defined for particles dispersed in hydrated solvents. Polymer coverage remained essentially constant with varying solvent composition. Optimum dispersion and maximum zeta potential occurred at a concentration of phosphate ester which corresponded to initial monolayer coverage. A maximum in the zeta potential also occurred at the azeotrope solution of MEK-ethanol and again coincided with optimum dispersion.Conductivity data indicate a dynamic adsorption-desorption dissociation mechanism for the ionic phosphate ester at the solid/liquid interface. The adsorption and conductivity data indicate the mechanism of dispersion stability is a combination of electrostatic and steric phenomena. |
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