Moessbauer study of brick: spectral analyses and temperature dependence of Fe ratio

Six clay samples, each fired to six different temperatures in the range of 1000-12500C, were studied by Moessbauer spectroscopy and powder X-ray diffraction. Hematite, mullite, and a glass phase were identified as the dominant species which contain iron in these fired brick samples. In all the samples there is a partial substitution of Al(III), which reduces the effective magnetic field. The iron is in the Fe(III) state and is predominantly in the tetrahedral site. Two of the samples were examined at both room temperature and 77K. The magnetic field increases in the lowering of the temperature, but the quadrupole splitting remains constant. This indicates that there is no Morin transition between 77K and room temperature. The physical properties of the resulting fired bricks were examined to determine the quality of each brick. Two of the samples were identified as clay not suitable for the production of good bricks. These two particular clays can be distinguished from the others by their Moessbauer parameters. (Auth.)