Low energy 4f-5d transitions in lanthanide doped CaLaSiN3 with low degree of cross-linking between SiN4 tetrahedra

CaLaSiN₃ samples doped with Eu, Yb, Sm, Ce and Pr have been prepared via solid-state reaction synthesis and the optical properties have been studied. Both Yb and Sm were only observed in the trivalent state due to the fact that their Ln²⁺ ground states are located inside or very close to the conduction band of the CaLaSiN₃ host lattice. Doping with Ce³⁺ or Eu²⁺ resulted in a very low energy Ce³⁺ or Eu²⁺ 4f-5d absorption band around 1.9 eV (650 nm) and 1.4 eV (885 nm), respectively. The Ce³⁺ 5d-4f emission appeared to be quenched, just as the Eu²⁺ 5d-4f emission, which can be explained as the result of auto-ionization.