Investigation of physical properties of Mn doped lead phosphate glasses

Abstract

Mn doped lead phosphate glasses (MnLPG) as (40-x)%P₂O₅-40 % PbO-16.5%Na₂O-3.5%Al₂O₃-xMnO₂ (x = 0, 1, 2, 3 and 4 %) matrix system are prepared by the melt-quenching method. The physical properties have been performed using several techniques such as X-Ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), Fourier Transform InfraRed spectroscopy (FTIR), Raman spectroscopy, UV–Visible properties, photoluminescence (PL) and EPR (electron paramagnetic resonance). XRD confirms the amorphous character of the glasses. DSC reveals an improvement of the glass transition temperature T_g values by increasing the density ρ and the oxygen packing density OPD and decreasing the molar volume V_m which leads to have a network glass more compact and tightly packed and reticulates the phosphate groups. The Infrared and Raman results show an opposite behaviour with a broken of the phosphate structure and the disruption of the P–O–P linkages. The optical spectra present absorption bands characteristic of Mn³⁺ and Mn²⁺ ions octahedral transition. Mott and Davis model presents a decrease of the band gap energy winth the MnO₂ addition. The Urbach energy ΔE_urb shows an increase with increase of manganese amount which is related to the increase of the structural disorder degree as the rate of manganese increases. The EPR spectrum of the 4 % Mn doped glass is characterized by a strong resonance signal centered at g near 2.0 another weak signal at g∼4.3 with no hyperfine structure. PL spectra exhibit emission bands corresponded to the oxygen defects presented in the glass and the appearance of a new band assigned to the Mn²⁺ ions as high as Mn increases.