Luminescence enhancement and energy transfers of Ce3+ and Sm3+ in CaSrSiO4 phosphor

Orthosilicate phosphors with desirable properties are used as commercial materials in the fields of lighting and display. Herein, a series of Ce3+ and Sm3+ singly- or doubly-doped CaSrSiO4 phosphors with charge compensations by co-doping of Na+ ions were successfully prepared using a conventional solid-state method and their crystal structures were determined from XRD profiles and refinement with the Rietveld method. Emphatically, Ce3+ or Sm3+ singly-doped CaSrSiO4 phosphors exhibited good photoluminescence properties. In doubly-doped phosphors, the red emission of Sm3+ was enhanced by energy transfer (ET) from Ce3+ to Sm3+ ions. The mechanism of ET was deduced to be dipole–dipole interaction using the Inokuti–Hirayama (I–H) model. The red emission intensity of Ca0.97Sr0.97Ce0.01Sm0.02Na0.03SiO4 at 425 K was 85.21% of that at 300 K, indicating satisfactory thermal stability of fluorescence. The obtained white LED device fabricated with Ca0.97Sr0.97Ce0.01Sm0.02Na0.03SiO4 phosphor, Sr2SiO4:Eu2+ and an ultraviolet (UV) chip displayed a bright white light with CIE chromaticity coordinates (0.32, 0.38), correlated colour temperature (CCT) of 6056 K and colour rendering index (Ra) of 73.5.