Thermal and structural properties of magnesium tetraborate produced by solid state synthesis and precipitation for use in thermoluminescent dosimetry

• Published in: Radiation physics and chemistry (Oxford, England : 1993) England : 1993), 2019-11, Vol.164, p.108382, Article 108382
• Main Authors: Freire de Souza, Luiza, Caldas, Linda V.E., Junot, Danilo O., Silva, Anderson M.B., Souza, Divanizia N.
• Format: Article
• Language: English
• Subjects: Chemical precipitation; Dehydration; Differential thermal analysis; Dosimeters; Dosimetry; Dysprosium; Hydroxyl groups; Luminescence; Magnesium compounds; Magnesium tetraborate; Optical properties; Organic chemistry; Pellets; Phosphors; SEM images; Sensitivity; Sintering; Solid state; Synthesis; Thermal analyses; Thermoluminescence
• ISSN: 0969-806X; 1879-0895
• DOI: 10.1016/j.radphyschem.2019.108382

Magnesium tetraborate is a phosphor with relevant characteristics for radiation dosimetry purposes. One of the main challenges on this material is still the understanding of its structure and luminescent processes involved in dosimetric performance. In this work, all the steps of the material production through DTA/TG, XRD and SEM techniques were evaluated to understand the main physical and chemical changes during the thermal process (calcination and sinterization) to produce the MgB4O7 samples. Two synthesis processes of MgB4O7 were studied: precipitation (P.S) and solid state (S.S). Finally, the luminescence efficiency of the pellets was investigated in function of different sintering temperatures. The initial stage of DTA/TG curves of the material just after the mixing of starting materials, regardless the synthesis, is marked by endothermic events caused by dehydration, decomposition of hydroxyl groups and hydrated borate phases. At higher temperatures, the curves are marked by exothermic events related to crystalline transitions, but the peak obtained for the S.S is better defined in comparison to P.S. Moreover, the DTA/TG analyses of the pellets prior and after the sinterization, showed that the process is more relevant for the MgB4O7 pellets produced by S.S (950 °C), dramatically reducing its higroscopicity. The SEM images reinforce the importance of the sintering process to create a resistant detector and with a more homogenous and cohesive surface, therefore increasing it luminescence properties. The thermoluminescent (TL) sensitivity of MgB4O7:Dy0,5% pellets produced via S.S, sintered at 950 °C, is 4 times higher compared to the ones sintered at 950 °C, via P.S. The materials produced via P.S did not present relevant changes in their TL sensitivity for sintering temperatures above 400 °C. •Production of magnesium tetraborate for radiation dosimetry.•Correlation of the synthesis steps with its final thermoluminescence efficiency.•Solid state and precipitation routes.•DTA/TG to identify the physical changes at calcination and sinterization.•Sinterization improving the sensitivity in the detectors.