J.Ma. Rincón, M. Romero. Characterization of mullite/ZrO 2 toughness ceramic materials microstructure by medium voltage analytical electron microscopy Materials Characterization, 45 (2000) 117-123; DOI: 10.1016/S1044-5803(00)00058-9 Characterization of mullite/ZrO 2 toughness ceramic materials microstructure by medium voltage analytical electron microscopy J.Ma. Rincón, M. Romero Instituto de Ciencias de la Construcción Eduardo Torroja, CSIC, C/Serrano Galvache 4, 28033 Madrid, Spain Abstract A series of mullite/ZrO 2 and mullite/alumina/ZrO 2 high-toughness ceramic materials have been examined by analytical electron microscopy (AEM) at 300 kV and by using the following techniques: energy dispersive X-ray (EDX) microanalysis, microdiffraction and convergent beam electron diffraction (CBED). The relative advantages and disadvantages for the analysis at higher voltages on the investigation of advanced ceramics are compared with results obtained at 120 kV. Keywords: TEM/EDX; Medium voltage analytical electron microscopy; Ceramics; Mullite; Zirconia 1. Introduction In order to explore the high-toughness properties of mullite/ZrO 2 ceramics, it is of great interest to determine the composition at grain boundaries and in the phases which constitute these composite materials. Therefore, analytical electron microscopy (AEM) experiments have been performed [1] and [2] to characterized the microstructure of mullite/ZrO 2 composites obtained by reaction sintering with CaO, MgO, or TiO 2 as sintering aids. These experiments were carried out in an AEM instrument operating in transmission electron microscopy (TEM)/energy dispersive X-ray (EDX) mode at 120 kV.