Synthesis and Crystal Structure of the Short <i>Ln</i>Sb₂O₄Br Series (<i>Ln</i> = Eu–Tb) and Luminescence Properties of Eu³⁺-Doped Samples

• Main Authors: Felix C. Goerigk, Veronica Paterlini, Katharina V. Dorn, Anja-Verena Mudring, Thomas Schleid
• Format: Article
• Language: English
• Published: MDPI AG 2020-11-01
• Series: Crystals
• Subjects: lanthanoid compounds; halide oxoantimonates(III); structure elucidation; luminescence characterization; solid-state synthesis; single-crystal X-ray diffraction
• Online Access: https://www.mdpi.com/2073-4352/10/12/1089

Pale yellow crystals of <i>Ln</i>Sb₂O₄Br (<i>Ln</i> = Eu–Tb) were synthesized via high temperature solid-state reactions from antimony sesquioxide, the respective lanthanoid sesquioxides and tribromides. Single-crystal X-ray diffraction studies revealed a layered structure in the monoclinic space group <i>P</i>2₁/<i>c</i>. In contrast to hitherto reported quaternary lanthanoid(III) halide oxoantimonates(III), in <i>Ln</i>Sb₂O₄Br the lanthanoid(III) cations are exclusively coordinated by oxygen atoms in the form of square hemiprisms. These [<i>Ln</i>O₈]¹³⁻ polyhedra form layers parallel to (100) by sharing common edges. All antimony(III) cations are coordinated by three oxygen atoms forming ψ¹-tetrahedral [SbO₃]³⁻ units, which have oxygen atoms in common building up meandering strands along [001] according to <inline-formula><math display="inline"><semantics><mrow><mmultiscripts><mrow><mo stretchy="false">{</mo><msup><mrow><mo stretchy="false">[</mo><msubsup><mrow><mi>SbO</mi></mrow><mrow><mn>2</mn><mo>/</mo><mn>2</mn></mrow><mi>v</mi></msubsup><msubsup><mi mathvariant="normal">O</mi><mrow><mn>1</mn><mo>/</mo><mn>1</mn></mrow><mi>t</mi></msubsup><mo stretchy="false">]</mo></mrow><mo>–</mo></msup><mo stretchy="false">}</mo></mrow><mo>∞</mo><mn>1</mn></mmultiscripts></mrow></semantics></math></inline-formula> (<i>v</i> = vertex-sharing, <i>t</i> = terminal). The bromide anions are located between two layers of these parallel running oxoantimonate(III) strands and have no bonding contacts with the <i>Ln</i>³⁺ cations. Since Sb³⁺ is known to be an efficient sensitizer for <i>Ln</i>³⁺ emission, photoluminescence studies were carried out to characterize the optical properties and assess their suitability as light phosphors. Indeed, for both, GdSb₂O₄Br and TbSb₂O₄Br doped with about 1.0–1.5 at-% Eu³⁺ efficient sensitization of the Eu³⁺ emission could be detected. For TbSb₂O₄Br, in addition, a remarkably high energy transfer from Tb³⁺ to Eu³⁺ could be detected that leads to a substantially increased Eu³⁺ emission intensity, rendering it an efficient red light emitting material.