Total emissivity of silicon at high temperatures

The total emissivity of four samples of silicon of different resistivities is measured in the temperature range 880-1550 K. The emissivity depends on carrier concentration in the silicon samples. As the temperature increases the emissivity increases, shows a maximum at about 950 K and then starts decreasing. After showing a broad minimum at about 1200 K, it starts increasing again. The actual values of the emissivity vary from about 0·42 to 0·78 depending upon the temperature and the resistivity of the sample.