Structural and electronic characteristics of pure and doped ZnO varistors

doi:10.1088/1674-1056/21/11/116103

摘要/Abstract

摘要： We report here structural, surface morphology, mechanical, and current-voltage characteristics of Zn_1-xM_xO ceramic samples with various x and M (0.00 ≤ x ≤ 0.20, M = Ni, Cu). It is found that the considered dopants do not influence the well-known peaks related to the wurtzite structure of ZnO ceramics, while the shapes and the sizes of grains are clearly affected. The average crystalline diameters deduced from the SEM micrographs are between 2.06 μ and 4.8 μ for all samples. The oxygen element ratio is increased by both dopants. Interestingly, the potential barrier can be formed by adding Cu up to 0.20, while it is completely deformed by 0.025 Ni addition. The breakdown field can be enhanced up to 4138 V/cm by 0.025 Cu addition, followed by a decrease with further increase of Cu up to 0.20. On the other hand, a gradual decrease in Vickers microhardness is reported for both dopants, and the values in the Ni samples are higher compared to those in the Cu samples. The electrical conductivity is generally improved by Ni, while the addition of Cu improves it only in the over doped region ( ≥ 0.10). These results are discussed in terms of the differences of valency and ferromagnetic ordering.

关键词: semiconductors, chemical synthesis, impurity, electronic transport

Abstract: We report here structural, surface morphology, mechanical, and current-voltage characteristics of Zn_1-xM_xO ceramic samples with various x and M (0.00 ≤ x ≤ 0.20, M = Ni, Cu). It is found that the considered dopants do not influence the well-known peaks related to the wurtzite structure of ZnO ceramics, while the shapes and the sizes of grains are clearly affected. The average crystalline diameters deduced from the SEM micrographs are between 2.06 μ and 4.8 μ for all samples. The oxygen element ratio is increased by both dopants. Interestingly, the potential barrier can be formed by adding Cu up to 0.20, while it is completely deformed by 0.025 Ni addition. The breakdown field can be enhanced up to 4138 V/cm by 0.025 Cu addition, followed by a decrease with further increase of Cu up to 0.20. On the other hand, a gradual decrease in Vickers microhardness is reported for both dopants, and the values in the Ni samples are higher compared to those in the Cu samples. The electrical conductivity is generally improved by Ni, while the addition of Cu improves it only in the over doped region ( ≥ 0.10). These results are discussed in terms of the differences of valency and ferromagnetic ordering.

Key words: semiconductors, chemical synthesis, impurity, electronic transport

中图分类号: (Alloys )

61.66.Dk

81.05.Gc (Amorphous semiconductors) 73.61.Jc (Amorphous semiconductors; glasses) 62.40.+i (Anelasticity, internal friction, stress relaxation, and mechanical resonances)

A. Sedky, E. El-Suheel . Structural and electronic characteristics of pure and doped ZnO varistors[J]. 中国物理B, 2012, 21(11): 116103-116103.

A. Sedky, E. El-Suheel. Structural and electronic characteristics of pure and doped ZnO varistors[J]. Chin. Phys. B, 2012, 21(11): 116103-116103.

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