Luminescence of a new class of UV–blue-emitting phosphors MSi2O2–δN2+2/3δ:Ce3+(M = Ca, Sr, Ba)

The luminescence properties of Ce3+,Na+-codoped MSi2O2−δN2+2/3δ (M = Ca, Sr, Ba) are reported. The undoped and Ce3+,Na+-codoped MSi2O2−δN2+2/3δ powders were prepared by a solid-state reaction at temperatures between 1300–1400 °C under N2–H2 (10%) atmosphere in the system MO–SiO2–Si3N4 (M = Ca, Sr, Ba). MSi2O2−δN2+2/3δ (M = Ca, Sr, Ba) crystallizes in the monoclinic system with different crystal structures. For excitation in the 300–360 nm range, MSi2O2−δN2+2/3δ:Ce3+ shows typical broad emission bands peaking at about 392, 473 and 396 nm for M = Ca, Sr and Ba, respectively. In particular, CaSi2O2−δN2+2/3δ:Ce3+ shows an unusual short-wavelength emission (∼392 nm) with a very small Stokes shift of 2200 cm−1; BaSi2O2N2:Ce3+ shows an interesting white-light emission in the visible range 350–600 nm for excitation at 365 nm.