TY  - EJOU
AU  - Habibullayev, Navruzbek 
AU  - Yurev, Ilya 
AU  - Molokeev, Maxim 
AU  - Aleksandrovsky, Aleksandr 
AU  - Trofimova, Olga 
AU  - Shulaev, Nikita 
AU  - Volkova, Svetlana 
AU  - Andreev, Oleg 

TI  - Synthesis, Crystal Structure, Optical, and Thermal Properties of a Novel Quaternary Selenide EuErAgSe<sub>3</sub>
T2  - Chalcogenide Letters

PY  - 
VL  - 
IS  - 
SN  - 1584-8663

AB  - A novel quaternary selenide, EuErAgSe<sub>3</sub>, has been synthesized for the first time. The phase forms upon annealing in the 1120–1800 K range and retains its crystal structure upon cooling to ambient conditions. The phase was prepared by the ampoule method from EuSe and AgErSe<sub>2</sub> powders, followed by annealing at 1270 ± 10 K for up to 300 h. Powder X-ray diffraction revealed that EuErAgSe<sub>3</sub> crystallizes in the AgBiS<sub>2</sub> structure type (space group <i>Fm-</i>3<i>m</i>) with the lattice parameter a = 5.95322(14) Å. The microhardness of the phase is 340 ± 15 HV. The optical band gap for direct transitions is 1.78 eV, and for indirect transitions, it is 1.36 eV. The phase begins to form in the temperature range 1120–1170 K, likely due to diffusion processes, and melts incongruently at 1830 ± 30 K. The formation of EuLnAgSe<sub>3</sub> phases was predicted for Ln = Gd–Lu, Y and confirmed experimentally for Gd, with a = 5.9906(4) Å, and for Yb, with a = 5.9312(5) Å. In the EuLnAgSe<sub>3</sub> series, the unit cell parameter decreases linearly with the ionic radius of Ln<sup>3+</sup>.
KW  - Quaternary rare-earth selenides; cation-disordered cubic structure; optical band gap; incongruent melting; artificial intelligence

DO  - 10.32604/cl.2026.085815