Effect of route production and doping concentration on luminescence response of MgB4O7: Gd phosphor

Abstract

This work studied the synthesis route and gadolinium (Gd) doping concentration on magnesium tetraborate (MBO) luminescence response. The material was synthesized by solid-state reaction techniques with two different procedures (Routes A and B) for three different Gd concentrations (0.2, 0.3, and 0.7 %wt). Route A consisted of the synthesis of the MBO matrix and subsequently add Gd2O3 as an activator. Route B the material was obtained after mixing and co-milling the precursors and the activator together prior to synthesis. Rietveld refinement of experimental X-ray diffraction data indicates that the MgB4O7:Gd compounds exhibit single phases consistent with orthorhombic symmetry (space group Pbca (61)). These compounds also evidenced contributions Gd dopant concentrations in MgB4O7 matching the cubic symmetry of the material. The electron microscopic scan surface morphological study exhibited the formation of polycrystalline material with diverse grain shapes for the two production routes. Compositional characterization by electron X-ray energy spectroscopy suggested that there were no other elements besides the expected elements in the material. The optical response by diffuse reflectance spectroscopy estimated the energy gap from the fundamental absorption of the undoped host. Optically stimulated luminescence response suggested that MgB4O7:Gd 0.7%wt (route B) sensitivity is 2.1 times higher than that presented in MgB4O7:Gd 0.3 % (route A). Thermoluminescence experiments showed that the optimum Gd dopant concentrations for the most intense dosimetric peak of phosphorus MgB4O7 fabricated using routes A and B were 0.3 % (main peak: 209 °C) and 0.7 % (main peak: 276 °C), respectively. The thermoluminescence sensitivity of MgB4O7:Gd 0.3%wt (route A) is 3.5 times higher than the sensitivity of MgB4O7:Gd 0.7%wt (route B).