Transparent polycrystalline SrREGa sub(3)O sub(7) melilite ceramics: potential phosphors for tuneable solid state lighting

Full and congruent crystallization from glass is applied to the SrREGa sub(3)O sub(7) melilite family (RE= Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Y). This innovative process enables the synthesis of polycrystalline ceramics exhibiting high transparency both in the visible and near infrared regions, despite tetragonal crystal structures and micrometer scale grain sizes. Moreover, glass crystallization provides an original route to synthesize new crystalline phases which are not accessible via a classic solid state reaction, as demonstrated for SrYbGa sub(3)O sub(7) and SrTmGa sub(3)O sub(7). To illustrate the potential optical applications of such materials, SrGdGa sub(3)O sub(7) transparent polycrystalline ceramics are doped with Dy super(3+) or Tb super(3+)/Eu super(3+) in order to generate white light emission under UV excitation. It is foreseen that such transparent melilite ceramic phosphors, prepared via a cost-effective process, can be successfully used in solid state lighting devices of considerable technological interest.