PREPARATION OF TRANSPARENT MgAl2O4 CERAMICS BY PULSED ELECTRIC CURRENT SINTERING USING TWO-STEP HEATING METHOD

Transparent MgAl2O4 ceramics were fabricated by pulsed electric current sintering (PECS) employing a two-step sintering mode. First, nanoscale MgAl2O4 powders were produced by solution combustion synthesis from hydrated nitrate compounds and urea. Subsequently, the synthesized powders were sintered by PECS with a heating rate of 100 degrees C/min under an applied pressure of 100 MPa. The sintering process was conducted according to a two-step heating profile. At the first step, the temperature increased to 1050, 1100, and 1150 degrees C, followed by a dwell time of 60 min. The second-step sintering was carried out at 1300, 1350, and 1400 degrees C for 20 min. The transparent ceramics sintered at 1050 degrees C / 60 min - 1400 degrees C / 20 min exhibited transmittance over 80% in infrared range. In addition, transparent samples presented a Vickers hardness up to 30 GPa for sintering mode of 1150 degrees C / 60 min - 1400 degrees C / 20 min.