Synthesis and characterization of Fe and P substituted 3 : 2 mullite

The incorporation in mullite structure of foreign elements has been studied since 1924. In this paper the isovalent 1/2P plus 1/2Al for Si substitutio n has been investigated employing wet chemistry preparative route with a fi nal firing temperature of 1300 degreesC. The extent of solid solution and t he crystallographic features of the end term with composition Al6.22Si1.56P 0.22O13 are described on the basis of XRPD profile fitting. This substituti on has also been examined in the presence of the contemporary Fe for Al sub stitution; the end term of this coupled isovalent compositional series Al5. 90Fe0.20Si1.80P0.10O13 has been characterized too. In this latter case, the crystallographic results are confirmed by Mossbauer spectroscopy. The simp le Fe for Al substitution at 1300 degreesC has also been reexamined in the same preparative conditions. The composition and the structure of the end t erm (Al-5.60)Fe0.40Si2O13) are in agreement with previous studies. The inco rporation degree of Fe and P in the coupled substitution results in being a pproximately halved in respect to simple substitutions of the two elements. (C) 2001 Elsevier Science Ltd. All rights reserved.