Blue emission and color-tunable behavior in Tm3+ singly- and Dy3+/Tm3+ co-doped CaLaGa3O7 phosphors

Tm3+ singly- and Dy3+/Tm3+ co-doped CaLaGa3O7 phosphors were prepared successfully by a high-temperature solid-state reaction method and their structure, spectroscopic properties, as well as energy transfer processes between Dy3+ and Tm3+ were studied. The XRD measurements show that all the prepared phosphors have a tetragonal structure. The emission proved that under excitation by 355 nm, 455 nm blue light was obtained in Tm3+: CaLaGa3O7 phosphor with a high color purity (99%). For Dy3+/Tm3+: CaLaGa3O7, the emission spectra exhibited the typical yellow emissions of Dy3+ and blue light of Tm3+. More importantly, the relative emission intensity of Dy3+ and Tm3+ can be varied by modifying the concentration of Tm3+ and the exciting wavelength, indicating that the luminescence color is tunable. Further, optimal white-light emission was achieved when co-doped 0.01 Tm3+ and 0.02 Dy3+ under 355 nm excitation. Meanwhile, the CIE chromaticity coordinates, color temperature value and color purity of the 0.02 Dy3+/0.01 Tm3+: CaLaGa3O7 phosphor were calculated to be (x = 0.3321, y = 0.3231), 5515 K and 7.18%, respectively, which are close to the standard white-light illumination. Moreover, the study on the decay curves indicates that mutual energy transfers between Dy3+ and Tm3+ take place in the Dy3+/Tm3+: CaLaGa3O7 phosphor. The above findings suggest that the prepared phosphors have potential applications in light emission devices.