Comparison of the crystal chemistry of tellurium (VI), molybdenum (VI), and tungsten (VI) in double perovskite oxides and related materials

Site-Selective d10/d0 Substitution in an S = 1/2 Spin Ladder Ba2CuTe1–xWxO6 (0 ≤ x ≤ 0.3)

“…It has been noted that perovskites containing W 6+ and Mo 6+ exclusively form double perovskite structures, whereas Te 6+ -containing perovskites can also adopt hexagonal structures. 57 The W 6+ and Mo 6+ cations inability to form hexagonal structures stems from the differences in metal–oxygen bonding involving d 0 versus d 10 cations. In the case of Te 6+ , the filled 4d 10 orbitals limit the d-orbital contribution to metal–oxygen bonding, creating a significant s- and p-orbital contribution in Te–O bonding.…”

“…Perovskites containing W 6+ and Mo 6+ exclusively form double perovskite structures, whereas Te 6+ containing structures can also adopt hexagonal structures. 53 The reason for this lies in differences in metal-oxygen bonding. Owing to the filled d-orbitals, metal-oxygen bonding with Te 6+ has a significant s and p orbital contribution that directs the electron density towards the oxide anions and away from the octahedral face.…”

“…Owing to the filled d-orbitals, metal-oxygen bonding with Te 6+ has a significant s and p orbital contribution that directs the electron density towards the oxide anions and away from the octahedral face. 53 This reduces the cation-cation repulsion associated with face-sharing octahedra, and such affects will help reduced the energy associated with the Te 6+ occupation of the B''(f) site. The opposite is true for W 6+ in perovskites where π-bonding interactions lead to highly regular [WO6] 6octahedral units creating a more spherical charge distribution that leads to relatively high repulsion across shared octahedral faces.…”

“…54 or tetragonal symmetry. 53 It is the difference in metal-oxygen bonding that drives W 6+ to form tetragonal Ba2CuWO6 to maximize the cation distances, while Te 6+ can accommodate face-sharing in hexagonal Ba2CuTeO6. This highlights the importance of considering more than ionic radii to predict crystal structures.…”

Band Gap Reduction in Ferroelectric BaTiO3 Through Heterovalent Cu-Te Co-Doping for Visible-Light Photocatalysis

“…The observed bond lengths seem to be consistent with the assigned valencies of 2+ for Cu and 6+ for Te. Due to the larger ionic radius of Cu 2+ than Te 6+ , all Cu-O bond lengths are found to be longer than Te-O bond lengths ( Longo and Raccah, 1973 ; Shannon, 1976 ; Flores et al, 2019 ).…”