Enhancing the Quality of the Characteristic Transmittance Curve in the Infrared Region of Range 2.5-7 μ m of the Optical Magnesium Fluoride (MgF2) Ceramic Using the Hot-Pressing Technique in a Vacuum Environment

This paper carries out an experimental study to enhance the quality of the characteristic transmittance curve in the infrared range of 2.5-7 μm of the optical magnesium fluoride (MgF2) ceramic. This work evaluates the effectiveness of using vacuum environment in the MgF2 ceramic hot-pressing technique by comparing the density and the quality of the transmittance characteristic curve of two types of specimens manufactured by the hot-pressing technique corresponding to open air and vacuum environment under the same technological parameters including temperature 650°C, time 30 min, and pressure 200 MPa. The results present that, in comparison with using the hot-pressing technique in the open air, when using the hot-pressing technique in a vacuum environment, the transmittance increases about 4-10%, the characteristic transmittance curve is smoother and has fewer peak points, and the wide of peak points are smaller. When hot-pressing in a vacuum environment, the temperature can be up to 750°C in order to obtain the magnesium fluoride (MgF2) ceramic with the highest quality of characteristic line in the infrared range of 2.5-7 μm. Seventeen specimens are manufactured to conduct the experimental study in order to figure out the optimal set of technological parameters (temperature T = 640.9°C, time t = 33.0 min, and pressure P=231.4 MPa) when hot-pressing in a vacuum environment by the experimental planning approach. © 2020 Nguyen Tuan Hieu et al.