Structural Optical and Luminescence Studies on Combustion Synthesized Metal Doped Mg2b2o5 Nanophosphors

Abstract

newlineLuminescence is an important phenomenon which finds many applications from day to day life to state of art devices such as paints, glow in dark appliances, solid state lighting, radiation dosimetry, scintillators, energy harvesting devices, optical memory devices etc. Therefore there is a growing demand to develop new luminescent materials (phosphors) which can be tailored for these applications. Here, In this present thesis, we investigated structural, reflectance, photoluminescence and thermoluminescence studies of t-Mg2B2O5 nanophosphors synthesized using optimized combustion method relatively at much lower temperature. The rietveld refinement of X-ray diffraction data confirms single-phase triclinic crystal structure of Mg2B2O5 nanophosphors. The direct band gap determined using diffuse reflectance spectra (DRS) was 5.23 eV, which is contrary to earlier reports quoting Mg2B2O5 as indirect band gap material. To elucidate the nature of band gap in Mg2B2O5, we performed first principle calculations based on full potential linearized augmented plane-wave (FPLAPW) method, predicting the direct band gap of 5.10 eV in t-Mg2B2O5 which is in good agreement with our experimental results. The t-Mg2B2O5 nanophosphors were found to exhibit yellow-reddish photoluminescence peaking at 588 nm, attributed to various defects states. The combustion synthesized Mg2B2O5 nanophosphors exhibited ultraviolet (254 nm) responsive thermoluminescence (TL). TL glow curve of Mg2B2O5 comprises of one dominant peak around 417 428 K and less intense shoulder around 573 589 K which arouse possibility of various trapping sites or defects present in the sample. The TL analysis using general order Kitiand#8223;s equations was performed to estimate the activation energies of trapping states.