Microhardness, microstructure and electrical properties of ZVM ceramics

doi:10.1007/s40145-014-0120-2

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Abstract

The effect of Mn₃O₄ addition on microhardness, microstructure and electrical properties of vanadium oxide doped zinc oxide varistor ceramics is systematically investigated. The Vicker's microhardness H_V has decreased with increasing the amount of Mn₃O₄. Also, the average grain size has decreased from 27.51 μm to 19.55 μm with increasing the amount of Mn₃O₄ up to 0.50 mol%, whereas an increase in Mn₃O₄ up to 0.75 mol% has caused the average grain size to increase and then it decreases with increasing Mn₃O₄ from 0.75 mol% to 1.00 mol%. The sintered density has decreased from 5.38 g/cm³ to 5.31 g/cm³ with increasing the amount of Mn₃O₄. The varistor ceramic modified with 0.50 mol% Mn₃O₄ has exhibited excellent nonlinear properties, with 16.29 for the nonlinear coefficient and 441.9 μA/cm² for the leakage current density. Furthermore, the sample doped with 0.50 mol% Mn₃O₄ has been found to possess donor density as 0.77×10¹⁸ cm^-3 and 0.916 eV barrier height.

Key words： ceramics electrical properties microstructure varistor Mn₃O₄ doped ZnO–V₂O₅ varistor

Received: 28 May 2014 Published: 12 June 2015

Corresponding Authors: Mohamed T. DAWOUD

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	Abdel-Mageed H. KHAFAGY
	Sanaa M. EL-RABAIE
	Mohamed T. DAWOUD
	M. T. ATTIA

Cite this article:

Abdel-Mageed H. KHAFAGY,Sanaa M. EL-RABAIE,Mohamed T. DAWOUD, et al. Microhardness, microstructure and electrical properties of ZVM ceramics[J]. Journal of Advanced Ceramics, 2014, 3(4): 287-296.

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http://jac.tsinghuajournals.com/EN/10.1007/s40145-014-0120-2 OR http://jac.tsinghuajournals.com/EN/Y2014/V3/I4/287

Average calculated values of density ρ, Vicker's microhardness H_V, molar volume V and grain size D as found from both XRD and SEM results

Compositional dependences of the sintered density ρ and the Vicker's microhardness H_V of xMn₃O₄–0.5V₂O₅–(99.5–x)ZnO ceramics sintered at 900 ℃ for 5 h, where x changes from 0 to 1.00 mol%.

SEM micrographs of xMn₃O₄–0.5V₂O₅–(99.5–x)ZnO samples: (a) x = 0.00 mol%, (b) x = 0.15 mol%, (c) x = 0.30 mol%, (d) x = 0.50 mol%, (e) x = 0.75 mol% and (f) x = 1.00 mol%.

Dependence of XRD patterns of tested ceramic varistors on the mole percentage of Mn₃O₄ content.

EDX analyses for the ceramic varistors with x = 0.15, 0.50 and 1.00 mol% of Mn₃O₄ at the interior of ZnO grain ((a), (c) and (e)) and on the grain boundary ((b), (d) and (f)).

Compositional dependence of J–E characteristics of tested varistor ceramics xMn₃O₄–0.5V₂O₅–(99.5–x)ZnO, where x = 0, 0.15, 0.30, 0.50, 0.75 and 1.00 mol%.

Average calculated values of the breakdown field E_B, nonlinear coefficient α, leakage current density J_L, barrier height φ_B, donor concentration N_d, density of states N_s, barrier width ω and non-ohmic conductivity σ

Compositional dependences of both the breakdown field E_B and average grain size D of xMn₃O₄–0.5V₂O₅–(99.5–x)ZnO ceramics.

Variations of average values of the nonlinear coefficient α and the leakage current density J_L as functions of mole percentage of Mn₃O₄ content.

Variations of the barrier height φ_B and the donor density N_d with the mole percentage of Mn₃O₄ content.

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