Preparation And Luminescence Properties Of Ba₂TiP₂O₉ White Light Emitting Phosphors

Since the first white-light emitting diode (WLED) came into being in 1996, more and more interests have been focused on them because they have a lot of advantages on long lifetime, lower energy consumption, and eco-friendly etc. With WLED developing rapidly, LED illumination is coming in commercialization and displaying great potential in landscape illumination, backlight of the liquid crystal and optical communications fields.Nowadays, three routes can be used to obtain the white LED, viz. exciting a yellow phosphor by blue LED, mixing the red, green and blue color emitted chips, and combining a UV light LED with a white-color phosphor. In these methods, the third one has been used widely because the color purity and the color temperature of white LED could be readily controlled by adjusting the position of the emission wavelength and the thickness of the white phosphors. And thus it is crucial to select the proper phosphors for the white LED. At present, the white-light emitting phosphors are usually synthesized by mixing the red, green and blue color phosphors . However, duo to the re-absorption of emission colors and proportional control of phosphors in the mixture, the lumen efficiency and color reducibility of white LED are influenced largely. Consequently, the synthesis of a single full-color white emitting phosphors will be significant.In this paper, the self-activated White-light emitting phosphors Ba₂TiP₂O₉ were synthesized by co-precipitation and high temperature solid reaction method. The resulting samples were characterized by x-ray diffraction, scanning electric microscope, emission spectra and the CIE chromaticity diagram. The results showed that had a monoclinic crystal structure, the excitation spectra with the peak at 254nm showed a broad excitation band in about 200-300nm wavelength region, under the 254nm irradiation, it emit a bright white light with a chromatic coordinate of (0.2191, 0.2927), which extended from 350 to 700nm and centered at 470nm.In addition, the effects of the pH value of initial solution and annealed temperature on luminescent properties of the phosphors were also studied. It was found that the width and intensity of emission spectra both firstly increased and then decreased with the increase of the pH values, and reached to the maximum when the pH value was 9, which was clearly explained by the DLVO theory. The optimal calcining temperature is selected at 1000℃for co-precipitation.