Studies of the optical properties of sodium copolyphosphate glasses

Abstract

A number of samples of glassy sodium polyphosphate and copolyphosphates of sodium — cobalt, sodium — copper, sodium — nickel, sodium-manganese and sodium — calcium were prepared and their optical properties were investigated. The ultraviolet and visible spectra of these glasses were recorded at the room temperature. It was found that the fundamental absorption edge of these glasses usually occurs in the ultraviolet — visible region. The optical absorption edges ( E 0) were calculated by using the relation α h ν = B ( hν − E 0) 2 where B is constant. The linear variation of (α hν) 1/2 with hν where α is the absorption coefficient and hν is the incident photon energy, is taken as evidence of non-direct interband transitions. The E 0 values obtained for copolyphosphate glasses appeared to depend on the size of the counter cation. The infrared spectra of all these glasses appeared to be almost the same, indicating the presence of characteristic P  O  P linkages of linear polyphosphate chains and two non bridging oxygen atoms bonded to phosphorus atoms O  P  O (PO 2) units in the polyphosphate tetrahedra.