Resumen de A comparative study between the addition of nano and micro-particles of Co_(3)O_(4) on the electrical and microstructural properties of a ceramic system based on SnO_(2)
M.I. Miranda López, M. B. Hernández, B.S. Vera Barrios, Alberto Toxqui Terán, J. A. Aguilar Martínez
A comparative study between the addition of Co_(3)O_(4) micro-particles and nano-particles as a densifying dopant of a SnO_(2) based varistor system was conducted. The ceramic composition was (99.9-X) %SnO_(2)-X % Co_(3)O_(4) -0.05 %Cr_(2)O_(3)-0.05 %Nb_(2)O_(5) where X = 0, 0.5, 1.0, 2.0 and 4.0 mol%. Two particle sizes of Co3O4 were used (∼ 5 µm and ∼ 50 nm). The addition of 0.5 mol% of Co_(3)O_(4) nano-particles promoted an increase of grain size of the sintered samples up to 7.9 µm, that is, the maximum value among all variations. Characterization techniques such as TGA, DTA, XRD, and Rietveld analysis revealed a decrease of 16◦C in the formation temperature of Co_(2)SnO_(4) as well as an increase of 2.6 wt% in the amount of such phase with the use of 4.0 mol% of Co_(3)O_(4) nano-particles in comparison with micro-particles. Statistical analysis indicated that the addition of nano-particles of Co_(3)O_(4) yielded better repeatability on the densification of ceramic samples. Also, residual porosity was decreased. Electrical breakdown and non-linear coefficient values correspond to a non-ohmic behavior with a potential application for manufacturing high voltage varistors. The findings of this work can be used as a reference for conducting a later study to improve the electrical properties or even to lower the sintering temperature.
