Comparison of Different Synthesis Methods to Produce Lithium Triborate and Their Effects on Its Thermoluminescent Proper
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UCTION
BORATES as host lattices are attractive candidates in thermoluminescence dosimetry (TLD). Thermoluminescence (TL) or thermally stimulated luminescence (TSL) is usually applied in the field of radiation. TL materials that are used in personnel or medical dosimetry have to possess tissue equivalence with the human body, and these dosimetric materials have nearly the same effective atomic number as that of human tissue. Lithium borate is a suitable material for radiation dosimetry, especially radiation therapy and clinical applications, because they have nearly tissue equivalent absorption coefficient (Zeff = 7.3) and an easy handling process. Lithium triborate LiB3O5 is a well-known lithium borate compound. This product may be a promising material for personal dosimetry because it is chemically inert to body fluids, nontoxic, and tissue equivalent.[1–3] However, the literature survey indicated that the TL properties and appropriate recombination processes in doped or undoped LiB3O5 are not fully studied when compared with Li2B4O7. Therefore, more investigation is needed to improve the TL characteristics of the lithium triborate compound. Lithium triborate is generally synthesized from the starting materials B2O3 and Li2CO3 at a high temperature. However, it is difficult to obtain a single-phase compound, because LiB3O5 melts incongruently and decomposes at 868 K ± 20 K (–253 C) and 1107 K ± 4 K (–269 C). Therefore, some lithium borate compounds TOLGA DEPCI, Assistant Professor, is with Faculty of Engineering and Architecture, Department of Mining Engineering, Yuzuncu Yil University, 65080 Van, Turkey. Contact e-mail: [email protected] GULHAN OZBAYOGLU, Professor, Doctor, is with Faculty of Engineering, Atilim University, 06531 Ankara, Turkey. AYSEN YILMAZ, Associated Professor, is with the Department of Chemistry, Middle East Technical University, 06531 Ankara, Turkey. Manuscript submitted June 27, 2009. Article published online June 26, 2010 2584—VOLUME 41A, OCTOBER 2010
like tetraborate (Li2B4O7), pentaborate (LiB5O8), and lithium octaborate (Li2B8O13) can be present in the lithium triborate phase.[4–8] Two aims are accomplished in the current research: One aim is to investigate the different preparation methods, which included were high-temperature solid-state (HTS) reaction, microwave-assisted hightemperature solid-state (MAS) reaction, and precipitation-assisted high-temperature solid-state (PAS) reaction to produce LiB3O5 as a single-phase powder. A literature survey showed that no studies have investigated the synthesis of LiB3O5 by MAS, which has been used to synthesize lithium triborate for the first time in this research. The second purpose of this study is to determine the effect of the synthesis methods on TL properties of doped lithium triborate.
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EXPERIMENTAL PROCEDURE
A. Synthesis of LiB3O5 1. HTS Reaction Method The experimental procedure was based on the study conducted by O¨zdemir et al.[1] In their work, lithium triborate was synthesized with small amount of impurities by the solid-state reactio
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