New Preparation Process and Influencing Factors of Strontium Tetraborate (SrB4O7)

Two hydrated strontium borate (SrB2O4·4H2O and SrB6O10·5H2O) were synthesized by liquid-phase precipitation method, and pure phase strontium tetraborate (SrB4O7) was obtained by high temperature calcination. The phase compositions, morphology and the high temperature sintering process of products were characterized by XRD, SEM, TG-DTA and chemical composition analysis. The effects of calcining temperature and holding time were investigated. The results show that the process of dehydration→amorphization→crystallization exists in the calcination of hydrated strontium borate. SrB6O10 is unstable at 800oC, and decomposed into SrB4O7 and liquid boron oxide. Pure strontium tetraborate was obtained with SrB2O4·4H2O and SrB6O10·5H2O as raw materials, which were calcined at 900oC for 4 h. With the increasing of reaction time, the crystallization degrees of products are improved, but the crystal structures are unaffected essentially. SrB4O7:Eu phosphors were prepared using this method. It is also found that the emission intensity from the sample is higher than that synthesized using SrCO3 and H3BO3 as raw materials.