| abstract |
An aluminum nitride sintered body having an oxygen concentration of notnlarger than 400 ppm, a metal impurity concentration of not larger than 150 ppm, andna carbon concentration of not larger than 200 ppm, and having an average crystalngrain size of 2 µm to 20 µm exhibits particularly excellent optical properties such asnan inclination of a spectral curve in the wavelength region of 260 to 300 nm of notnsmaller than 1.0 (%/nm), a light transmission factor of not smaller than 86% in thenwavelength region of 400 to 800 nm, and a wavelength of not longer than 400 nmnwhen the light transmission factor reaches 60% in the spectrum. |