Sanitaryware reference industrial experimental compositions have been formulated, formed by slip casting and subsequently sintered in a laboratory electric furnace. Microstructural evolution was followed by HRTEM, BSE, X-ray diffraction and infrared spectroscopy. Thermal evolution of raw materials shows dehydroxylation of kaolinite, transformation to spinel and mullite, and transformation of α-quartz into β-quartz. Principal discussions are focused on the spinel and mullite evolution in the 900-1300 οC temperature range. Evidence of the phase trans formation from spinelto mullite were found in single crystals characterized locally by fast Fourier transformand lattice fringe d spacing accounting for the coexistence of nanometric mullite with the cubic spinel phase. Back scattered electrons (BSE) in topographic mode have been used to show the presence of the spinel type intergrowth plates within the sanitaryware microstructure. Aspect ratio calculations and interplanar analysis of the distances shows less characteristic planes of spinel as mullitization and vitrification progresses, mullite planes increase up to 1250 οC and decrease at 1300 οC.

Keywords: Spinel, Mullite, Sanitaryware, Microstructure, Hrtem, Infrared spectroscopy.