Structural and optical properties of erbium doped phosphate glass containing zinc oxide nanoparticles

Abstract

Understanding and examining the influence of metallic nanoparticles (NPs) on structural and optical properties of phosphate glass has become tremendous topical interests. A series of glasses with composition (78.5-x) P2O5–10Li2O–10ZnO–1.5Er2O3–(x) ZnO (with 0 = x = 1.2 mol%) were prepared using melt quenching technique and their detailed characterizations were performed. The amorphous nature of the glass was confirmed using X-ray diffraction (XRD) technique. The estimated NPs average sizes are 8.54 nm by using Debye-Scherrer formula. The glass stability S, the onset of Tg and Tc were measured by using differential thermal analyser (DTA). The mode of vibrations for these glasses was analyzed using Fourier transform infrared (FTIR) spectroscopy. FTIR measurements revealed that the presence of ZnO NPs increased the depolymerisation of the glasses at Q3 tetrahedral sites. FTIR spectra exhibit five peaks which are assigned to P=O group at Q3 tetrahedral site (1310 cm-1), PO2 group (1260–1170 cm-1), P-O- groups (1080 and 900 cm-1) and P-O-P groups (775–710 cm-1). The results affirmed that the incorporation of ZnO NPs improved the chemical and physical stability of the phosphate glass. The UV-Vis absorption spectra comprised of eight absorption bands corresponding to the transitions 4F3/2, 4F3/2, 4F7/2, 2H11/2, 4S3/2, 4F9/2, 4F9/2 and 4I9/2. The band gap energy was found to increase from 3.54 to 3.59 eV and the Urbach energy decreased from 0.258 to 0.246 eV as obtained from the UV-Vis absorption measurements. The influence of ZnO NPs on the luminescence property of Er3+ as dopant was studied and the mechanisms involved in the enhancement on emission intensity was determined using photoluminescence spectroscopy at 357 nm excitation. The emission spectra consist of eight peaks in which the peak intensity of the violet band centered at 413 nm for 4F3/2 ? 4I15/2 transition and blue band at 458 nm due to 4F7/2 ? 4I15/2 transition showed gradual increment with increased concentration of ZnO NPs added to the glass. The enhancement in the emission peak intensity for the transition is attributed to the effect of quantum confinement and local field of ZnO NPs in the vicinity of Er3+ ion. The correlation between structural and optical properties in the presence of NPs is established.