ChemInform Abstract: CREEP OF POLYCRYSTALLINE MGO-FEO-FE2O3 SOLID SOLUTIONS

Steady-state creep experiments were performed on hot-pressed polycrystalline MgO doped with Fe. Dead-load 4-point bend creep tests were conducted at stresses of 26 to 270 kg/cm2, at temperatures of 1250° to 1450°C, in O2 partial pressures of 1 to 10−9 atm, on specimens with grain sizes of 10 to 65 μm. Viscous steady-state creep was always observed when the grain size was stable. Experiments at variable PO2's and temperatures were used to identify regimes of high (117 ± 10 kcal/mol) and low (81 ± 5 kcal/mol) activation energy. In the latter, creep rates were nearly independent of Fe dopant concentration and PO2, whereas in the former creep rates were enhanced by increasing PO2's and Fe dopant levels. The high- and low-activation-energy regimes were interpreted as diffusional creep controlled primarily by Mg lattice diffusion and O grain-boundary diffusion, respectively.