Synthesis, crystal structure, spectroscopic properties, and electronic structure of a new borate, EuCd3(AlO)3(BO3)4

Highlights: • A new gaudefroyite phase, EuCd₃(AlO)₃(BO₃)₄, has been synthesized and characterized. • It demonstrates a red emission due to ⁵D₀.→⁷F_j (j = 1, 2, 3, 4) electronic transitions of Eu³⁺ ions. • The band electronic structure has also been investigated. -- Abstract: A new europium borate EuCd₃(AlO)₃(BO₃)₄ has been prepared by the high-temperature solution reaction at 850 °C and structurally characterized by single crystal XRD analyses. It belongs to gaudefroyite type of structure, crystallizing in the polar hexagonal space group P6₃ with a = 10.390 (2) Å and c = 5.7244 (14) Å. Its structure features a three-dimensional framework composed of 1D [AlO₄]_n⁵ⁿ⁻ chains that are bridged by BO₃ triangles, with small channels accommodating Eu³⁺/Cd²⁺ ions only and big channels hosting Eu³⁺/Cd²⁺ ions together with BO₃ groups. The existence of BO₃ groups was confirmed by vibrational spectroscopy. The photoluminescence of EuCd₃(AlO)₃(BO₃)₄ was studied. The emission spectra consist of groups of lines in the red spectral region due to ⁵D₀→⁷F_j (j = 1, 2, 3, 4) electronic transitions of Eu³⁺ ions and the decay curves show the biexponential behavior. Moreover, band electronic structure has also been investigated.