Preparation And Luminescence Properties Of Rare Earth/Transition Metal Ions-Doped Tetracalcium Phosphate Phosphors

Phosphate phosphors are important and conventional light-emitting material and widely used in lighting and display owing to stable physical and chemical properties, low preparation temperature, cheap and complex host structure, which can absorb ultraviolet light strongly and enables efficient emission in the visible spectrum range. Rare-earth Eu2+ and transition metal ions(Cu+, Mn2+, Cr2+, Fe2+, Co2+, Ni2+) doped tetracalcium phosphate Ca4(PO4)2O phosphors were pepared, respectively. The main achievements are summarized as follows:A. A novel less expensive rare-earth free Ca4(PO4)2O:Cu+ yellow phosphor was prepared under reducing atmosphere of 8%H2/N2. The emission spectra located between 400-800 nm and peaked at 585 nm corresponding to 3d94s-3d10 transition of Cu+ and an ultra-broad band with FWHM of ~200 nm. The existence of multi-Cu+ luminescent centers in Ca4(PO4)2O host was identified to be the origin of ultra-broad band for the phosphor. Superiority in generating high CRI white light by combining with BAM blue phosphor comparing with the traditional combination of trichromatic phosphors was demonstrated. White light with CRI value as high as about 94.3 was achieved by employing the less expensive rare-earth free Ca4(PO4)2O:Cu+ phosphor. Furthermore, the influence of concentration of active ions, charge compensation agent and flux to luminescent properties were investigated.B. A varieties of low-valence transition metal-dope yellow phosphors: Ca4(PO4)2O:Mn, Ca4(PO4)2O:Cr, Ca4(PO4)2O:Fe, Ca4(PO4)2O:Co, Ca4(PO4)2O:Ni under reducing atmosphere of 8%H2/N2 were prepared to exhibit similar luminescent performance to that of Ca4(PO4)2O:Cu+. The emission spectrums were located between 400-800 nm with a peak at 580 nm in ~200 nm of FWHM for d-d transition.C. Color-tunable emission of Eu2+ doped calcium-phosphate based phosphors owing to the phase evolution of luminescent host was demonstrated. Red emission peaked at 675 nm was tuned to blue emission peaked at 480 nm as the calcium-phosphate luminescent host evolved from Ca4(PO4)2O(TTCP) to α-Ca3(PO4)2(α-TCP) by increasing calcination temperature from 1400 ?C to 1500 ?C. The 5d-4f transition of Eu2+ activators doped in TTCP/α-TCP host is responsible for the broad red/blue emissions.D. A varieties of Eu and low-valence transition metal ions(Cu, Mn, Cr, Fe, Co, Ni) co-doped Ca4(PO4)2O phosphors were pepared under reducing atmosphere of 8%H2/N2. A overlap exists across part of excitation spectrum of Ca4(PO4)2O:Eu2+ and the emission spectrum of transition metal ions doped Ca4(PO4)2O, energy transfer probably occured between Eu2+ and low-valence transition metal ions to induce Eu2+ red light emission under excitation of 325 nm while commonly-recognized, quenching was also observed under the excitation of 470 nm.