Enhancing the blue luminescence behaviour of the Li co -doped novel phosphor ZnB2O4: Tm 3+

Abstract

Here we report a detailed structural analysis, and properties of the cathodoluminescence (CL), photoluminescence (PL) and 3D thermoluminescence spectra of the Tm3+ incorporated ZnB2O4 phosphor successfully synthesized through wet-chemical synthesis. The formation of a single-phase compound is verified through X-ray diffraction (XRD) studies. The phosphor shows an efficient blue emission located at 458 nm corresponding to 1D2→3F4 under both a low voltage electron beam and UV excitation. The optimal concentration of the doped Tm3+ is 0.5 mol% in CL and PL measurements. The corresponding concentration quenching mechanism is confirmed to be a multipole-multipole interaction, and the critical distance between Tm3+ ions is estimated to be 34 Å. Incorporating Li+ remarkably enhances the luminescence intensity probably because of the charge compensation effect. Li ions are speculated to fill the defects in the ZnB2O4 host and then the excitation energy transfers from the host to Tm3+. Surprisingly, the thermoluminescence spectra of ZnB2O4:Tm3+ and Li+ co-doped ZnB2O4:Tm3+ recorded in the temperature range 30–400 °C follow a different pattern compared with PL and CL data. The dominant signals come from Tm3+ sites. Above room temperature, the Tm3+ ions do not show the peak temperature movement, but do exhibit a different pattern with the addition of co-doped Li+ ions. These results indicate that these phosphors are promising candidates for luminescence-based optoelectronic devices.