Abstract
Nano-sized tetragonal BaTiO3 (BT) particles that are well dispersed in solution are essential for the dielectric layer in multilayer ceramic capacitor technology. A hydrothermal process using TiCl4 and BaCl2, as source of Ti and Ba, respectively, or the precursor TiO2 as seed for the formation of BT, and poly(vinylpyrrolidone) (PVP) as a surfactant, was employed in this study to enhance both the dispersibility and tetragonality (c/a) simultaneously in a single reaction process. The process parameters, i.e., the ratio of TiO2 substitution of TiCl4, the reaction time, and PVP content were systematically studied, and the growth mechanism and relation between the tetragonality and the particle size are discussed. Dynamic light scattering (DLS) analysis was used to show that truncated pseudo-tetragonal BT-PVP particles with an average size of 100 nm, having a narrow size distribution and a coefficient of variation (CV) as low as 20% and being mono-dispersed in water, were produced. The narrow particle size distribution is attributed to the ability of PVP to inhibit the growth of BT particles, and the high c/a of BT-PVP to heterogeneous particle growth using TiO2 seeds.
Highlights
Miniaturization and capacity enlargement of multilayer ceramic capacitors (MLCCs) are essential for the generation of electronic devices; the dielectric material used in these MLCCs requires thinner dielectric layers and a grain size below a few hundred nanometers [1]
The X-ray diffraction (XRD) results indicate that the phase of the BT-PVP nanoparticles is pseudo-tetragonal and that it is independent from the Ti source
This paper reports our study of the hydrothermal process in which BaTiO3 (BT) particles were produced using the source compounds TiO2 as the seed oxide and PVP as the surfactant
Summary
Miniaturization and capacity enlargement of multilayer ceramic capacitors (MLCCs) are essential for the generation of electronic devices; the dielectric material used in these MLCCs requires thinner dielectric layers and a grain size below a few hundred nanometers [1]. BaTiO3 (BT) is the most important dielectric oxide material [2] and its industrial synthesis occurs by way of a solid-phase reaction involving high-temperature sintering Because this manufacturing procedure is not suitable for small particle sizes below a few hundred nanometers, many solution processes for the fabrication of BT have been attempted [3]. The solution process leads to low tetragonality, resulting in low dielectric constants, for which there are two reasons: (1) the size effect [7] reflecting a thermodynamic phase transition due to isotropic pressure and (2) the nonstoichiometric defects of BT [8] This size effect of BT is considered to be unavoidable for small particles, irrespective of the powder synthesis
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