Synthesis of MgB4O7 and Li2B4O7 crystals by proteic sol–gel and Pechini methods

Magnesium-tetraborates and lithium-tetraborates are excellent detectors for ionizing radiation. However, manufacturing these crystalline structures is challenging as it involves multi-step chemical processes and toxic reagents. Over the past decades, alternative production methods for crystals have been studied aiming at lowering production costs and environmental impact and at increasing production yield and reproducibility. Among these is the Pechini method, based on the formation of polymer chains containing uniformly distributed metal ions. Another method is a modified proteic sol–gel process using edible gelatins or coconut water instead of the alkoxides used in conventional processes. In this work, we searched optimal conditions for the synthesis of dosimetry-grade MgB4O7 and Li2B4O7 crystals with the Pechini and the proteic sol–gel methods. The crystal phases were characterized by X-ray diffraction and by thermal analyses. We determined that MgB4O7 can be synthesized either by calcination of the reagents at 900 °C for 2 h with the sol–gel approach, or at just 800 °C for 2 h with the Pechini method. Single-phase Li2B4O7 can be synthesized either by calcination of the reagents at 650 °C for 2 h with the sol–gel approach, or at just 600 °C for 2 h with the Pechini method. Our synthesis times and temperatures are lower than those reported in the literature, which reduces significantly production costs and environmental impact.