Synthesis, Crystal and Local Electronic Structures, and Photoluminescence Properties of Red-Emitting CaAl_zSiN_(2+z):Eu~(2+) with Orthorhombic Structure

摘要

Orthorhombic Ca_(1-x)Eu_xAl_zSiN_(2+z) polycrystalline powders have been synthesized by a solid-state reaction at high temperature in a nitrogen atmosphere. The smaller lattice parameters compared with the single crystal and charge distribution analysis indicate that impure oxygen might be incorporated into the lattice. Ca_(1-x)Eu_xAl_zSiN_(2+z) shows red emission at about 630 nm due to the transition of Af~65d~1→4f ~7 when excited within 375-450 nm. With an increase in the Eu~(2+) concentration and z, the quantum efficiency of Ca_(1-x)Eu_xAi_zSiN_(2+z). was significantly decreased due to concentration quenching and high photoionization. First-principle molecular orbital calculations suggest that the overall luminescence of Eu~(2+) may be mainly originated from the small Eu(1) center. CaSiN_2:Eu~(2+) is a potential red conversion phosphor for white LED applications.