Ba2B10O17: a new centrosymmetric alkaline-earth metal borate with a deep-UV cut-off edge

Abstract

A new centrosymmetric alkaline-earth metal borate, Ba₂B₁₀O₁₇, has been successfully synthesized through high-temperature solid-state reactions. The single-crystal X-ray structural analysis shows that Ba₂B₁₀O₁₇ crystallizes in the triclinic space group P. The parameters of the triclinic unit cell are a = 6.7128(3) Å, b = 9.8698(4) Å, c = 9.9998(4) Å, α = 76.860(3)°, β = 83.200(3)°, γ = 73.332(3)°, and Z = 2. The title compound features a [B₁₀O₁₇]_∞ three-dimensional anionic framework with infinite channels in which the Ba²⁺ cations are located. Ba₂B₁₀O₁₇ possesses a large experimental band gap of 6.29 eV and a short cut-off edge lower than 180 nm proved by the transmission spectrum on a single crystal sample 0.5 mm in thickness. The calculated band structures and the density of states of Ba₂B₁₀O₁₇ suggest that its indirect energy gap is 5.97 eV which agrees with the experimental result. The thermal behavior and the IR spectrum of Ba₂B₁₀O₁₇ are also reported in this work.