Solid-state synthesis, structure, second-harmonic generation, and luminescent properties of noncentrosymmetric BaSi7N10:Eu2+ phosphors

Abstract

Eu-doped BaSi₇N₁₀ phosphors were synthesized by high-temperature solid-state reactions and their structural and optical characteristics were investigated. The X-ray diffraction analysis shows that the phosphor crystallizes in the monoclinic noncentrosymmetric space group, Pc (no. 7). The second-harmonic generation measurements on BaSi₇N₁₀ using 1064 nm radiation reveal frequency doubling efficiency similar to that of KH₂PO₄ (KDP). With respect to the doped BaSi₇N₁₀, the SHG efficiencies decrease with Eu²⁺ doping. The particle size-dependent SHG characteristics revealed that BaSi₇N₁₀ is a type-1 nonphase matchable material. The phosphor shows photoluminescence (PL) emission at 475 nm, which could be attributed to the 4f⁶ 5d → 4f⁷ transition in the Eu²⁺ ion and the peak emission wavelength does not shift with more Eu²⁺ addition. The photoluminescent excitation (PLE) spectra show broad excitation in the range 250–400 nm peaking at 332 nm. The temperature-dependent PL emission exhibits small thermal quenching of the phosphor with thermal activation energy ΔE = 0.18 eV for the Ba_0.92Eu_0.08Si₇N₁₀ phosphor. The phosphor exhibits good surface morphology with uniformly hexagonal-shaped particles with an average size of 15 μm. The purity of emission was gauged by CIE coordinates (x, y) and the coordinates for the phosphor exhibiting maximum luminescence intensity were (0.18, 0.29).