Abstract

Infrared transmission peaks have been observed in binary mixtures of boron nitride with several other materials. In addition, pressed pieces of boron nitride alone display a similar peak. The dependence of the wavelengths of the peaks on the refractive index of the second material in mixtures is in accord with the Christiansen filter effect as the explanation of these observations. The similar behavior in pressed boron nitride is attributed also to the Christiansen filter effect arising from impurities known to be present. For most mixtures one peak occurs between 5 and 6 μ in wavelength and a second peak between 11 and 12 μ. These are associated, respectively, with the 7.3- and 12.3-μ absorption bands of the boron nitride. Furthermore, such peaks have been produced, apparently for the first time, on the long-wavelength side of these absorption bands by combining boron nitride with a matrix material of appropriately high refractive index. From these observations an approximate dispersion curve for boron nitride is deduced.

© 1961 Optical Society of America

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