The electronic structure and luminescence properties of Ce3+ doped Sr10[(PO4)5.5(BO4)0.5]BO2 under UV/VUV and X-ray excitation

• Typical 5d–4f transition of Ce3+ and defect-related luminescence of the host have been observed in Ce3+ doped sample.
• The small band gap and weak absorption in the VUV range of the host lattice have been clarified.
• The Ce3+ ion was demonstrated to occupy Sr3 site (6g, C1) in the host.
• The XEL and VUV–UV luminescence mechanisms have been investigated in detail.

The apatite related compound Sr10[(PO4)5.5(BO4)0.5]BO2 (SrBPO) doped with Ce3+ was synthesized via solid state reaction method. Undoped SrBPO shows blue-green emission under ultraviolet (UV) and X-ray excitation due to the defects in the host. When excited by vacuum ultraviolet–ultraviolet (VUV–UV) light or X-ray, Ce3+ doped SrBPO shows a broad emission band peaking at 450 nm originating from 5d–4f transition of Ce3+ and defects in the host. The phosphor exhibits strong excitation bands in UV range and a weak broad excitation band in VUV region. The site occupation of Ce3+ was proposed based on fluorescence decay curves. Electronic structure shows the compound is an indirect semiconductor with a band gap of 3.04 eV. The extremely small density of states of [PO4]3− or [BO4]5− group near Fermi level or in the conduction band is a possible origin of the weak excitation band in the VUV range. A possible mechanism was proposed to explain the luminescence properties observed.

Figure optionsDownload high-quality image (175 K)Download as PowerPoint slide