High-pressure synthesis, crystal structure, and electronic properties of Ba₉Zr_2.79Te₁₅

The polycrystalline Ba₉Zr_2.79Te₁₅ sample was prepared by employing a solid-state synthesis method under high-temperature and high-pressure conditions. Comprehensive characterizations of structural and electrical properties were performed. Ba₉Zr_2.79Te₁₅ crystallizes in a hexagonal lattice with the space group $P\overline{6}c2$ (No. 188) and lattice parameters a = 10.1977(8) Å and c = 20.2646(9) Å. It is mainly composed of face-sharing ZrTe₆ octahedral chains extending along the c-axis, which form a triangular lattice in the ab plane. The Te chains are located in the middle of the ZrTe₆ triangular lattice. Electrical transport measurements indicate that Ba₉Zr_2.79Te₁₅ is a semiconductor. The thermal activation band gap of 0.23 eV is qualitatively discussed when compared with that of its sister compound Ba₉Zr₃Se₁₅, proving that the p electrons in the Te chains, with high quantum number orbitals, dominate electron conduction. Furthermore, the Debye temperature of Ba₉Zr_2.79Te₁₅ is calculated to be 157.28(9) K from thermodynamic measurements. The newly synthesized Ba₉Zr_2.79Te₁₅ with quasi-one-dimensional chain characteristics provides an opportunity for further exploration of diverse physical properties.