Space charge characterisation by EDS microanalysis in spinel MgAl2O4

2020-02-29 23:18:25

boundary grain Al spinel stoichiometry

责任者: Nuns, N.;Beclin, E.;Crampon, J. 单位: Lab. de Struct. et Proprietes de lEtat Solide, Univ. des Sci. et Technol. de Lille, Villeneuve dAscq, France 来源出处: Journal of the European Ceramic Society(J. Eur. Ceram. Soc. (UK)),2005//,25(12):2809-11 摘要: It was already showed that spinel presents a grain boundary sliding deformation accommodated by diffusion during creep at high temperature [Beclin, F., Duclos, R., Crampon, J. and Valin, F., Microstructural superplastic deformation in MgO·Al2O3 spinel. Acta Metall. Mater. 1995, 43, 2753-2760; Addad, A., Etude de la plasticite haute temperature de materiaux ceramiques spinelle-zircone. Ph.D. thesis, Laboratoire de Structure et Proprietes de lEtat Solide, Villeneuve dAscq, 1995]. A space charge layer at grain boundary in ionic ceramics can explain the observed interface reaction controlling diffusion at low stress (less than 60MPa). The nonstoichiometric area due to ionic defects should create an electrostatic potential between the grain surface and inside grain. The purpose of this work is to study the grain boundary region stoichiometry to confirm this theory. Fine-grained spinel (average grain size under micron), which presents an interface reaction at low stresses, is studied by TEM nano-scale microanalysis. The cation ratio Al/Mg variation is well described. It varies from 2.34 at grain boundary to 2.10 at 100nm inside the grain. The ratio Al/O shows no variation across the grain boundary and suggests that the stoichiometry defect observed is due to an excess of magnesium vacancies located at the grain boundary. [All rights reserved Elsevier] 关键词: ceramics;grain boundaries;grain boundary diffusion;magnesium compounds;space charge;stoichiometry;stress effects;surface chemistry;transmission electron microscopy;vacancies (crystal);X-ray chemical analysis;space charge characterisation;EDS microanalysis;spinel MgAl2O4;grain boundary sliding deformation;creep;high temperature effects;ionic ceramics;interface reaction controlling diffusion;stress effects;nonstoichiometric area;ionic defects;electrostatic potential;grain surface;grain boundary region stoichiometry;fine-grained spinel;TEM nanoscale microanalysis;cation ratio;Al-Mg variation;Al-O ratio;stoichiometry defect;magnesium vacancies;energy dispersive spectroscopy;MgAl2O4