Molten Salt Synthesis And Characterization Of Rare Earth Doped Vanadate And Borate Luminescence Materials

Rare earth doped Vanadate and Borate luminescent materials have been widely used in optics, electricity and so on due to their high luminescent intensities and stability under UV or VUV excitation as comparison with the conventional phosphors. However, synthesis of YVO4 powders has been mainly accomplished by solid-state reaction, but this method leads to high pollution, high invest, complex synthesis process, the low crystalline of the particles and bad morphology, so the synthesis of YVO4 powders by solid-state reaction can't demand the requirement of the environmental protection in the society. Molten salt synthesis method (MSS) as a novel power synthesis method, which developed in the recent years, has been extensively used in the synthesis of electronics ceramic and high-temperature compound oxide powder. If molten salt method can be used in the synthesis process of the YVO4 powders, the benefit of the economy and society must be achieved.In this study, Eu3+, Sm3+, Dy3+ and Dy3+/Tm3+ doped Vanadate (YVO4:Eu3+, YVO4:Sm3+, YVO4:Dy3+, YVO4:Dy3+/Tm3+) and Eu3+ and Tb3+ doped borate (YBO3:Eu3+, YBO3:Tb3+) were successfully prepared using NaNO3 or NaCl as the molten salt by molten salt synthesis method (MSS). The results indicated that grains with spherical morphology are homogeneous and nearly several hundred nano meters. The results were as follows:YVO4:Eu3+, YVO4:Sm3+, YVO4:Dy3+ and YVO4:Dy3+/Tm3+ were successfully prepared using NaNO3 or NaCl as the molten salt by MSS. All samples emit characteristic emissions of the doping rare earth ions under the excitation of UV light. The emission of YVO4:Eu3+ particles show emission originating from the D-5(0) level, with D-5(0)-F-7(2) at 616 nm as the most prominent group, the grain size is nearly 150 nm. The emission intensity can be improved by using Bi to replace part of the Y in YVO4:Eu3+ system.Luminescent materials YVO4:Sm3+ were successfully prepared using NaNO3 as the molten salt by molten salt synthesis method (MSS). The phosphors thus obtained were treated with different calcination temperatures and doping concentrations to get better luminescent properties. The results showed that the doped rare earth ion (Sm3+) showed it's characteristic emissions in YVO4 hosts. The emission at 647 nm due to 4G5/2â†'6H9/2 transition of Sm3+ ions was improved drastically by MSS method than other methods. All samples showed red emission and the best red light emission was observed with YVO4:1%(Sm3+) after calcinated at 500℃for 5hrs.Luminescent materials YVO4:Dy3+/Tm3+ were successfully prepared using NaNO3 as the molten salt by MSS. The doped Dy+/Tm3+ ions showed characteristic emissions in YVO4 hosts. The uniformity phase of Dy3+ and Tm3+ codoped YVO4 phosphor was checked by X-ray diffraction (XRD) technique. The relationship between the ratio of Dy3+/Tm3+ and the chromaticity had also been discussed. The results showed that the best white light emission was observed with YV04:Dy0.3/Tm0.7 (2%) after calcinated at 500℃for 5h.Eu3+ and Tb3+ doped Borate:YBO3:Eu3+, YBO3:Tb3+ were successfully prepared using NaNO3 as the molten salt by MSS. The particles were characterized by X-ray diffraction (XRD) and luminescence spectra (PL), respectively. The emission of YBO3:Eu3+ due to 5D0â†'7F1 and 5D0â†'7F2 transitions of Eu3+ ion. the emission of YBO3:Tb3+ due to 5D4â†'7Fn (n=3,4,5,6) transitions of Tb3+ ion.In our studies, the molten salt synthesis method will provide a novel and simple method for the preparation of good properties phosphors.