Synthesis of nanotabular barium titanate via a hydrothermal route
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David V. Miller Bectel-Bettis, West Mifflin, Pennsylvania 15122
Rajneesh Kumar, Jennifer A. Nelson, Clive A. Randall, and James H. Adair NSF Particulate Materials Center, Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802 (Received 9 November 2004; accepted 22 December 2004)
As layer thickness of multilayer ceramic capacitors decreases, nanoparticles of high dielectric materials, especially BaTiO3, are needed. Tabular metal nanoparticles produce thin metal layers with low surface roughness via electrophoretic deposition. To achieve similar results in dielectric layers requires the synthesis and dispersion of tabular BaTiO3 nanoparticles. In the current study, the synthesis of BaTiO3 was investigated using a hydrothermal route. Transmission electron microscopy and atomic force microscpy analyses show that the synthesized particles are single crystal with a 〈111〉 zone axis and a median thickness of 5.8 nm and face diameter of 27.1 nm. Particle growth is likely controlled by the formation of {111} twins and the synthesis pH, which stabilizes the {111} face during growth. With limited growth in the 〈111〉 direction, the particles develop a platelike morphology. Physical property characterization shows the powder is of high purity with low hydrothermal defect concentrations and controlled stoichiometry.
I. INTRODUCTION
With the recent demands placed on cellular and mobile technologies, the need for nanoparticles of highly engineered materials has increased. The high volume, low cost, and superior properties of passive electronic components requires that precision powders for electronic component are inexpensive, of high quality, and can be produced at high yields. Control of chemical and hydrothermal defects in the powders is of great importance in controlling the properties of multilayer ceramic capacitors (MLCCs) made from the powder. Therefore, the synthesis of high-quality powders with high dielectric properties, especially perovskite structured materials, has been of specific interest. The dependence of volumetric capacitance of a MLCC on the thickness of the active layer is well-documented.1 Nanoparticles and their assembly provide potential to reduce layer thickness below the current standard of 1 m. Much work on a variety of synthesis routes for the synthesis of BaTiO3 nanoparticle has occurred recently. Solid-state carbonate reactions,2 a modified Clabaugh
DOI: 10.1557/JMR.2005.0117 J. Mater. Res., Vol. 20, No. 4, Apr 2005
http://journals.cambridge.org
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process,3 low-temperature direct synthesis (LTDS),4 and several other routes5–7 have all been investigated. The first two routes are common commercial methods used to produce powders; however each requires further processing, either milling or calcination, to produce nanoscale BaTiO3, while powders produced by LTDS have a high hydroxyl defect concentration and a low Ba/Ti ratio. Hydrothermal synthesis is a common method that produces nanosized powders. Under the correct synthesis co
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