The Effect of Rare Earth Ion Dopants on the Grain Size of Y₂O₂S Phosphors

Abstract

Red light emitting phosphors (Y, Eu, Ln)₂O₂S were crystallized in (Li₂CO₃+S) fluxes containing various rare earth ions such as La³⁺, Nd³⁺, Gd³⁺, Yb³⁺ and Lu³⁺. According to the SEM observations, the grain size of (Y, Eu)₂O₂S was decreased by adding La³⁺, Nd³⁺ or Gd³⁺ ions, but increased by adding Yb³⁺ or Lu³⁺ ions. Such a profile was closely related to the changes of the unit cell parameters of (Y, Eu, Ln)₂O₂S. Addition of La³⁺ ions has given little effect on the luminescent properties and the formation reaction mechanism of (Y, Eu)₂O₂S. Furthermore, the minimum grain size of (Y, Eu)₂O₂S phosphor was obtained at 3mol% of La³⁺ doping. The flux growth mechanism was disscussed in the formation process of oxysulfides.