Photoluminescence and Fourier Transform Infrared Spectral Studies of Varying Levels of Manganese Doping in Zinc Phosphate Oxide Glasses

Zinc phosphate glasses with varying gradient Mn ion concentrations of x MnO-(57.5-x) ZnO-2.5Al2O3-40 P2O5 were prepared
by melting annealing. UV/Vis, Fourier transform infrared (FTIR), and photoluminescence (PL) spectrophotometric tests
examined the spectra and structural changes of the glassy samples. Electronic spectral graphs exhibit considerable ultraviolet
absorption with a distinct band shifting to slightly higher wavelengths with MnO2 addition and two more bands in glasses
with increasing manganese ion content (8–10%). FTIR spectral data show phosphate group vibrational peaks between 400
cm−1 and 1600 cm−1, assuming that Zn-O or P-O-Zn vibrations are shared. The PL spectra subsequently exhibited a wider
band in the range 500–750 nm and two-component peaks at greater manganese ion concentrations. As manganese ion concentration increases, divalent manganese ions of the known spin-forbidden absorption type that require high MnO2 content
are identifed. All spectral data suggest and validate the lack of trivalent manganese ions, and as the manganese ion concentration increases, divalent manganese ions of known spin-forbidden absorption type with high MnO2 content are detected.
The reducing nature of the host zinc phosphate glass favors the reduced valence of manganese ions