Electrical properties of polycrystalline ZnO:Cu obtained from freeze-dried ZnO + copper(II) acetate powders

• Published in: Journal of materials science. Materials in electronics 2002-08, Vol.13 (8), p.485-489
• Main Authors: BELLINI, J. V, MORELLI, M. R, KIMINAMI, R. H. G. A
• Format: Article
• Language: English
• Subjects: Acetates; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Copper; Density; Dielectric, piezoelectric, ferroelectric and antiferroelectric materials; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Electric fields; Electronics; Elements, oxides, nitrides, borides, carbides, chalcogenides, etc; Exact sciences and technology; Grains; Physics; Sintering; Studies; Zinc oxide
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1023/A:1016160204435

Highly homogeneous mixtures of powders containing ZnO and monohydrated copper(II) acetate, (CH^sub 3^COO)^sub 2^CuH^sub 2^O, AcCuH^sub 2^O were obtained by freeze drying. Thermal analysis and high-temperature X-ray diffraction showed that pure freeze-dried AcCuH^sub 2^O powder decomposed to CuO, in air, at temperatures above 325 °C. Due to the polymeric nature of AcCuH^sub 2^O, the powder mixtures were compacted without pressing additives. Pellets with ZnO+x mol % Cu (x=0.05, 0.5, and 5.0) compositions were sintered in air from 750 to 1150 °C for 1 h. After sintering, the density, shrinkage and mass loss increased as the concentration of AcCuH^sub 2^O increased. A microstructural analysis of samples sintered at 950 °C for 1 h revealed Cu-doped ZnO grains with Cu-clusters of x=5.0 mol % Cu; the J-E curves showed that both the breakdown electric field, E^sub br^, and the nonlinearity coefficient, α, increased as x increased from 0.05 to 0.5. Complex acceptor defects involving Cu^sup +^^sub Zn^ in the grain boundary are believed to have compensated for the n-type conductivity of the ZnO grains, giving rise to high E^sub br^ values.[PUBLICATION ABSTRACT]