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

Abstract

The luminescence properties of Ce³⁺,Na⁺-codoped MSi₂O_2−δN_2+2/3δ (M = Ca, Sr, Ba) are reported. The undoped and Ce³⁺,Na⁺-codoped MSi₂O_2−δN_2+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). MSi₂O_2−δN_2+2/3δ (M = Ca, Sr, Ba) crystallizes in the monoclinic system with different crystal structures. For excitation in the 300–360 nm range, MSi₂O_2−δN_2+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, CaSi₂O_2−δN_2+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.