Lattice parameters of some different chromium-doped mullites obtained by a
sol-gel route and sintered at 1650° C have been determined from X-Ray
Diffraction data as a function of both temperature and Cr contents. Profile
refinements on the X-ray diffraction diagrams have been carried out, showing
that, at temperatures between 800° and 1535° C, an anisotropic thermal
expansion takes place for the a and b
lattice parameters of the Cr-doped mullite. We show that this anisotropic
expansion is dependent on the temperature increase and the chromium content
for the different compositions of the mullite crystals.