Ba6(Bi1-xEux)9B79O138 (0 ≤ x ≤ 1): synergetic changing of the wavelength of Bi3+ absorption and the red-to-orange emission ratio of Eu3+

Very recently, a novel barium bismuth borate Ba6Bi9B79O138 (BBBO) was shown to be a new analogue of REBaB9O16 (RE = rare earth), which is a family of excellent phosphor hosts, because it has two types of cationic positions suitable for bi- and tri-valent activators (or sensitizers). In this study, we prepared Eu3+-to-Bi3+ substituted solid solutions Ba-6(Bi1-xEux)(9)B79O138 (0 < x < 1) and performed a systematic UV-photoluminescence investigation. As anticipated, efficient energy transfer occurs in the whole series of compounds and the majority of the energy absorbed by Bi3+ was transmitted to Eu3+, causing a great enhancement of Eu3+ emission. More interestingly, the Eu3+-to-Bi3+ substitution leads to a centrosymmetric-to-noncentrosymmetric transition of the local coordination symmetry of the trivalent cations due to the size difference between Eu3+ and Bi3+. This is observed in the synergetic changing of the wavelength of Bi3+ S-1(0) -> P-3(1) absorption (excitation spectra) and the red-to-orange emission ratio (emission spectra) when changing x. BBBO is a new polyborate host with a freshly resolved structure whose interesting preliminary results suggest the further development of BBBO-based phosphors.