Hydrothermal synthesis of calcium hexaborate pentahydrate from local boric acid and its photoluminescence characteristic

The aim of the study is to synthesize hydrated calcium hexaborates via a hydrothermal method with the use of local (obtained from Turkish deposits) boric acid. The effects of temperature and boric acid to water and calcium oxide to boric acid ratios on the phase formation were examined via X-ray diffractometry and scanning electron microscopy. Fourier transform infrared spectroscopy (FTIR) was used to study of chemical bonding and simultaneous thermal analysis (STA) was used to characterize thermal properties of the synthesized hydrated calcium hexaborate. The ideal synthesis conditions for the formation of calcium hexaborate pentahydrate were determined as 100 degrees C for temperature, 0.5 for boric acid to water molar ratio, and 0.05 for calcium oxide to boric acid molar ratio with the use of ammonium polymethacrylate as a dispersant. It was also found that impure iron from the local source results in a higher photoluminescence intensity in comparison to the one obtained from pure boric acid.