PbLnB7O13 (Ln = Tb or Eu): a new type of layered polyborate with multi-colour light emission properties

Two new lead rare-earth polyborates, PbTbB7O13 and PbEuB7O13, have been successfully synthesized via a high temperature molten salt method. Single crystal X-ray diffraction analysis reveals that they are isostructural and feature a 2D layer structure that contains alternating layers of [B7O13]∞ and [Tb]∞. The [B7O13]∞ layer is constructed of BO3 and BO4 groups with the fundamental building block of B7O17 (3Δ4□: <Δ2□>Δ<Δ2□>). Solid solutions of PbTb1-xEuxB7O13 (x = 0-1) were prepared via a solid state reaction and the photoluminescence properties were studied. The results show that under UV or near-UV excitation, the luminescence colour of samples of PbTb1-xEuxB7O13 (x = 0-1) can be tuned from green through yellow to red by simply adjusting the relative Eu3+ and Tb3+ concentrations, because of the Tb3+ → Eu3+ energy transfer mechanism.