Hg-free lamp is a green environmental-protective lighting energy now due to not containing harmful mercury vapor to people. In recent years, much of the investigation on this is being carried out. The excitation resource in Hg-free lamp mainly emits vacuum violet (VUV) photon of 147 and 172 nm, so exploring luminescent materials with strong absorption around these wavelengths is an important aspect to improve the luminescent efficiency of Hg-free lamp. A team from Laboratory of Function and Environment Materials in School of Physical Science and Technology of Lanzhou University has carried out much investigation on this subject, and a novel white-emitting luminescent material in one host under VUV excitation was identified. The corresponding research has been published on Journal of The Electrochemical Society, J. Am. Ceram. Soc., Electrochem. Solid St., Mater. Res. Bull.

The team explored some new VUV phosphors with phosphate as host. And the phosphate is an excellent host material for rare earth ions to dope owing to its high physical and chemical stability, strong absorption to VUV photon, and environmental-friendly characteristics. On one hand, the photoluminescence properties of Tb3+, Ce3+, Mn2+ ions were single or multi-doped in these hosts were investigated, and the excitation spectra in VUV-UV region and the emission spectra under 147 nm excitation were measured. The emitting color was tuned by varying the content of activator, finally white-emission was achieved. The energy-transfer relationship among multi-doped ions was also studied in this paper. On the other hand, they studied a VUV luminescent material with oxide as host, and Tb3+ with short decay time was chosen as activator. The VUV-UV excitation and emission spectra were measured, the quenching concentration of Tb3+ in this host was investigated, and the f-d transition of Tb3+ located at long-wavelength direction was also interpreted.

Excitation and emission spectra using synchrotron radiation at BSRF and the CIE chromaticity diagram. In the excitation spectrum, Tb3+ doped sample shows a broad and strong excitation band between 100 and 250 nm, which is beneficial to the emission wavelengths of Hg-free lamp; and two excitation peaks in UV region are found, which indicates this spectrum can match the light distribution in PDP and Hg-free lamp; from the CIE chromaticity diagram, it shows the luminescent color of the sample can be changed by varying the concentration of the three activators, and white emission has been achieved under certain concentration ratio.

The research result of this paper enriches the rare earth ions doped luminescence materials, and provides material for realizing white emission in single host. The energy-transfer relationship among multi-doped ions under VUV excitation is rarely reported, and we provide some theoretical basis and practical evidence for this.