Characterization of mullite-Nd2O3 composite prepared through spark plasma sintering
The present study investigated the microstructure and mechanical properties of spark plasma sintered mullite-Nd2O3 composite. 10 wt% Nd2O3 was added to the calcined mullite precursor using a simple mixing method after only 5 min of high energy milling in ethanol media and polyethylene cups. After that, two samples including mullite and mullite-Nd2O3 composite were spark plasma sintered at 1400 °C. The recorded XRD patterns demonstrated only mullite peaks in monolithic sample while Al2O3 and Nd2O3 peaks and dominant peaks of mullite in the case of mullite-Nd2O3 composite. FESEM micrographs and corresponding EDS elemental mapping investigations on the binary phase diagram and possible formed reaction products revealed the formation of Al2O3, SiO2, NdAlO5 and Nd2Si3O12 phases as eutectic reaction products. Nd2O3 improved the mechanical properties of mullite (bending strength of 461 ± 38 MPa, Vickers hardness of 16.25 ± 0.7 GPa and fracture toughness of 5.22 ± 0.14 MPa m1/2). Moreover, the spark plasma sintering process resulted in a nearly full density of both prepared samples.