Pioneering Exploration in the Na–Lu–B–O System: Na₃LuB₈O₁₅ with Polyborate Structure and Short UV Cutoff Edge

Na3LuB8O15, the first sodium lutetium borate in the Na–Lu–B–O system, was prepared by the spontaneous crystallization method. Na3LuB8O15 is crystallized in the centrosymmetric triclinic space group P1¯ with the following cell parameters: a = 6.4047(12)Å, b = 7.3342(13)Å, c = 13.081(2)Å, α = 88.999(7)°, β = 78.631(8)°, γ = 66.622(7)°, and Z = 2. The general configuration of Na3LuB8O15 can be characterized as a network structure created by infrequent multiboron anion chain skeletons [B8O17] and [LuO7] polyhedra shared by oxygen atoms, where Na ions are filled in the pores to balance charges. According to a UV–vis-NIR spectrum investigation, the chemical has a short ultraviolet cutoff edge (185 nm). Thermal analysis reveals incongruent melting compound properties. In addition, a first-principles calculation was conducted to delve deeper into the correlation between the performance and the structure.