Site engineering of Ce3+-doped calcium scandate phosphors and understanding of relevant red-shifted emitting from green to yellow

CaSc2O4:Ce3+ is a well-known green emitting phosphor, but needs to match with suitable red emitting phosphors in practical white lighting. Herein, a site engineering strategy is proposed to modify the local coordination environment of Ce3+ by introducing Y3+ and Mg2+ ions into the CaSc2O4 crystal lattice. The obtained results indicate in the modified Ce3+-doped samples (CSO-YMg), Y3+ ions can occupy both Sc3+ and Ca2+ sites simultaneously, and the Y3+ ions tend to occupy Ca2+ sites in low-doped stage and enter into the Sc3+ sites in the high-doped stage. The introduction of Y3+ ions gives rise to the existence of MgO in as-prepared CSO-YMg samples, and it can be effectively washed through pickling. In the spectral aspect, with the increase of Y3+ and Mg2+ ions, the main emission peak is red-shifted from 512 nm to 530 nm upon excitation at 450 nm. However, the high-doped sample presents much stronger thermally induced fluorescence quenching than CaSc2O4:Ce3+. The lattice defects caused by doped ions (Y3+ and Mg2+) and the non-radiative energy transfer process between the Ca2+ (Ce3+) and Sc3+ (Ce3+ or Ce4+) sites should be responsible for such evident quenching phenomenon in CSO-YMg, which is obviously different from the emitting feature of CaSc2O4:Ce3+ (only at Ca2+ sites). Besides, utilizing the as-prepared CSO-5 phosphors and a blue LED (~450 nm), a WLED was successfully fabricated, yielding a comparable performance to those with commercial Y3Al5O12:Ce3+ phosphors. What discussed in this study would bring some inspirations in the exploration and understanding of Ce3+-based phosphors according to local structural modification.