Oxoberyllates SrBeO2 and Sr12 Be17 O29 as Novel Host Materials for Eu2+ Luminescence

Abstract

Beryllate structures are marginally investigated, but show intriguing structural relations to oxo- and nitridosilicates. A typical feature is the coordination of Be in both trigonal planar and tetrahedral coordination by O. A broad range of structures is accessible by variable combinations of both building units. Three novel ternary Sr-oxoberyllates are characterized by single-crystal X-ray diffraction analysis, density functional theory calculations and investigations on luminescence properties: α-SrBeO₂ , β-SrBeO₂ and Sr₁₂ Be₁₇ O₂₉ are obtained with oxoberyllate substructures, made up of either BeO₃ triangles or BeO₄ tetrahedra. The compounds can be described as chain- and layer-type beryllates. When excited with blue light of (In,Ga)N LED chips, β-SrBeO₂ and Sr₁₂ Be₁₇ O₂₉ show visible emission in the yellow and orange spectral range, respectively, upon doping with Eu²⁺ . Exceptional narrow-band yellow emission (λ_em =564 nm, fwhm=55 nm) makes β-SrBeO₂ :Eu²⁺ a promising phosphor for application in phosphor-converted (pc-)LEDs.

Keywords: beryllates; luminescence; nitridosilicates; oxides; solid-state structures.