Optical characterization of black glasses from the ZnO-CdO-Al2O3-SiO2 composition system

Abstract

In recent years glasses with high transmission in the near infrared have become important for different technological applications. Several optical devices (high energy polarization devices, laser aligners, autocollimators, etc.) use black glass plates as transmission radiation windows in the near infrared and absorbers in the visible spectrum. Usually, by using conventional glass matrices such as phosphate, borate, borosilicate and silicate, black glasses with addition of different colouring agents for controlling optical transmission [1] have been obtained. Recently, black glasses in the CdO-A1203-SiO2 system useful for optical devices have been investigated [2]. New families of cadmium glasses have been reported in the ZnO-CdO-A1203-SiO2 system containing 12 wt % A1203 [3-5]. It is the aim of this letter to show the influence of composition on the spectral transmittance of black glasses in a ZnOCdO-A1203-SiO2 glass matrix with copper, manganese and selenium additions. A wide range of glasses with different compositions were prepared from ZnO, CdO and SiO2 covering the entire ZnO-CdO-AlzO3-SiO2 system [6]. Several glasses from this composition system have been prepared with similar CuO, MnO2 and Se additions (Table I). In addition, the 20ZnO'50CdO30SIO2 (wt%) composition with different CuO, MnO2 and Se additions was prepared. The raw materials used were reactive grade oxides. In order to homogenize the original mixture, ballmilling was used. Melting of the mixtures was carried out in alumina-silica crucibles in a Kanthal electric furnace at 1400-1450°C, followed by annealing and cooling heat treatment at 200 °Ch -1. The final appearance of the glasses is described in Table I. The spectral transmission was measured in the 200-2600nm range using a Perkin-Elmer 330 spectrometer with a 4 mm thick plate. The plate was embedded into Canada Balsam and glued to a glass holder. The sample was polished on both planes