Spectroscopic study of the TbAl3(BO3)(4) single crystal: Raman and luminescence spectroscopy

The vibrational and luminescence properties of the TbAl3(BO3)4 single crystal were studied in the temperature range of 5–300 K. Raman spectra of the single crystal revealed 5 of 7 A1 and all E phonon modes predicted by the group-theory analysis. The splitting energy between the LO and TO components of polar E phonons is determined. A group of intense bands associated with the 5D4 → 7F0 electronic transition was observed in the energy range of 14520–14680 cm−1 of the luminescence spectra. The intensity of these bands decreases upon heating. At the same time, the bands which can be assigned with 5D4 → 7F6, 5D4 → 7F5, and 5D4 → 7F4 transitions were revealed in luminescence spectra at room temperature. The intensity of these bands is comparable to the intensity of the Raman spectrum of TbAl3(BO3)4. The observation of luminescence from the 5D4 multiplet (20600–20750 cm−1) upon excitation at λexc = 632.8 nm (15803 cm−1) and λexc = 532 nm (18797 cm−1) indicates strong nonlinear properties of the studied crystal. The structure of the main 7F6 multiplet of Tb+3 in the TbAl3(BO3)4 single crystal has been studied at 5 K by Raman spectroscopy. The energies of the electronic levels of 7F6 and 5D4 multiplets were determined from the luminescence spectra measured at 300 K.