PHASE-STABILITY OF CHEMICALLY DERIVED ENSTATITE (MGSIO3) POWDERS

A modified Pechini chemical preparation technique was used to produce enstatite (MgSiO3) powder. By this method, low-temperature stable orthoenstatite (OE) was obtained at 850-degrees-C after 2 h of calcination. The effects of annealing temperature/time, initial particle size, chemical dopants, and shear stress on the conversion of protoenstatite (PE) to clinoenstatite (CE) on the powder have been studied. The results indicated that the transformation of orthorhombic PE to monoclinic CE was sensitive to the initial powder particle size as well as to the type and amount of chemical dopant used. Sodium ions (Na+), which were found to cause the formation of a glassy phase around the PE grains, destabilized the PE phase physically. In comparison, manganese ions (Mn2+), were found to preferentially substitute for the smaller Mg2+ ions in solid solution and stabilized the PE phase chemically. The powders with different chemical dopants were examined by TEM and EDS.