Luminescent Properties of Lanthanum Borates LaBO3:Eu and La(BO2)3:Eu Obtained by the Extraction-Pyrolytic Method

Lanthanum borates LaBO3, α-La(BO2)3 and La1 – хEuхBO3, La1 – хEuх(BO2)3 (х = 0.025, 0.05, 0.075, 0.10) were synthesized by the extraction-pyrolytic method. The key advantages of this method over known methods of borate synthesis are lower temperature and shorter time. The compounds were characterized by powder X-ray diffraction, IR spectroscopy, and luminescence spectroscopy. The orthoborates La1 – хEuхBO3 and metaborates La1 – хEuх(BO2)3 exhibit intense red luminescence in the 550–700 nm range. The nature of the luminescence spectra in the series of orthoborates La1 – хEuхBO3 or metaborates La1 – хEuх(BO2)3 does not change, which attests to identical local environments of the Eu3+ ion. The maximum luminescence intensity is observed for La0.95Eu0.05BO3 and La0.95Eu0.05(BO2)3 samples obtained by annealing for 2 h at pyrolysis temperatures of 750 and 800°С, respectively.