Abstract
Transparent MgAl2O4 ceramics were fabricated by pulsed electric current sintering (PECS) employing 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 100oC/min under an applied pressure of 100 MPa. The sintering process was conducted according to two-step heating profile. At the first step, the temperature increased to 1050, 1100, and 1150oC, followed by a dwell time of 60 min. The second-step sintering was carried out at 1300, 1350, and 1400oC for 20 min. The transparent ceramics sintered at 1050oC/ 60 min – 1400oC/ 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 1150oC/ 60 min – 1400oC/ 20 min.
Highlights
Transparent ceramics have received increasing attention from scientists owing to transmittance in a wide range of wavelengths, excellent mechanical properties, and resistance at high temperature [1,2,3,4,5,6,7]
The MgAl2O4 samples were virtually translucent at the second–step temperatures of 1300°C and 1350°C, while samples that were sintered at the second– step temperature of 1400°C became transparent regardless of first-step sintering temperature
The results suggested that the second-step sintering temperature had a significant influence on the transmission of materials rather than the first-step temperature
Summary
Transparent ceramics have received increasing attention from scientists owing to transmittance in a wide range of wavelengths, excellent mechanical properties, and resistance at high temperature [1,2,3,4,5,6,7]. Magnesium aluminate MgAl2O4 spinel is one of the most commonly-used transparent ceramics as it presents an isotropic crystal structure, which curbs diffuse transmission when the light passes through the material. This material allows light with wavelengths from the ultraviolet to the mid-infrared region to transmit through it [8]. Regarding material consolidation, pulsed electric current sintering (PECS) is well-known as a superior method to fabricate high-quality transparent ceramics [15, 16]. In addition to the conventional singlestep sintering process, a two-step heating method accompanied by PECS has been selected to produce transparent ceramics [20]. In a two-step heating profile, the first step is implemented at a low temperature, and subsequently, the temperature increases to the sintering temperature to densify the bulk
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