A porous mullite composition is made by Forming a mixture of one or more
precursor compounds having the elements present in mullite (e.g., clay,
alumina, silica) and a property enhancing compound. The property
enhancing compound is a compound having an element selected from the
group consisting of Mg, Ca, Fe, Na, K, Ce, Pr, Nd, Sm, Eu, Gd, Th, Dy,
Ho, Er, Tm, Yb, Lu, B, Y, Sc, La and combination thereof. The mixture is
shaped and to form a porous green shape which is heated under an
atmosphere having a fluorine containing gas to a temperature sufficient
to form a mullite composition comprised substantially of acicular mullite
grains that are essentially chemically bound.