Synthesis and characterization of lithium triborate by different synthesis methods and their thermoluminescent properties

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2009
Depci, Tolga
Lithium triborate, (LiB3O5), is a technologically important material for diverse applications, such as nonlinear optical materials and surface acoustic wave devices or, etc. Furthermore, it is suggested as an efficient thermoluminescent material. LiB3O5, suitable to dosimetric usage, was produced by different synthesis methods which were high temperature solid state reaction, microwave solid state reaction, microwave assisted high temperature solid state reaction and precipitation assisted high temperature solid state reaction. After the synthesis, metal oxides were doped into LiB3O5 to enhance its thermoluminescent properties. Identification and characteristics of LiB3O5 were determined by X-ray diffraction (XRD), Fourier Transform Infra red (FTIR) analyses, Differential Thermal Analyses (DTA), Scanning Electron Microscopy (SEM) and Particle Size Analyzer. The glow curves were obtained by using thermoluminescent (TL) reader. Among four different synthesis methods applied, high temperature solid state method needs very high temperatures and long duration of heating. Therefore, the effect of the reaction temperature, the time intervals, and also starting materials on production of LiB3O5 were investigated. Characterization studies indicated that LiB3O5 could be produced at 710 °C for 4 hours. Among the starting materials used, Li2CO3 and H3BO3 combination was found the most suitable for the synthesis of LiB3O5 considering phase impurity as well as cost. LiB3O5 synthesized by microwave energy was unsuccessful. However, LiB3O5 could be synthesized by microwave assisted synthesis method by adding distilled water, urea and sucrose separately as thermal auxiliaries in microwave pre-heating step. The use of microwave and conventional ovens subsequently shortened the duration of heating. The crystallinity of LiB3O5 was the best in 40 % sucrose addition to initial mixture. The best method for synthesis of LiB3O5 has been found as precipitation assisted high temperature solid state method. This method yields LiB3O5 with higher phase purity as compared to these produced by other methods applied in this thesis and reported in the literature. It seems to be rather attractive since it is simple and needs less energy. Rare earth metal oxides, CuO and Al2O3 were added to LiB3O5 as activators to improve its TL properties. LiB3O5 synthesized by precipitation assisted high temperature solid state reaction and doped by 5 % wt Al2O3 showed the best TL property. Its main dosimetric characteristics revealed that LiB3O5 seemed to be suitable to medical and radiotherapy applications, since it was non-toxic, tissue equivalent, and chemically inert to body fluids.

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Citation Formats
T. Depci, “Synthesis and characterization of lithium triborate by different synthesis methods and their thermoluminescent properties,” Ph.D. - Doctoral Program, Middle East Technical University, 2009.