Structural and optical properties of Ba(Co _1−x Zn _x )SiO ₄ ( x = 0.2, 0.4, 0.6, 0.8)

Structural characterization and X-ray reference powder pattern determination have been conducted for the Co- and Zn-containing tridymite derivatives Ba(Co _1−x Zn _x )SiO ₄ ( x = 0.2, 0.4, 0.6, 0.8). The bright blue series of Ba(Co _1−x Zn _x )SiO ₄ crystallized in the hexagonal P6 ₃ space group (No. 173), with Z = 6. While the lattice parameter “ a” decreases from 9.126 (2) Å to 9.10374(6) Å from x = 0.2 to 0.8, the lattice parameter “ c” increases from 8.69477(12) Å to 8.72200(10) Å, respectively. Apparently, despite the similarity of ionic sizes of Zn ²⁺ and Co ²⁺ , these opposing trends are due to the framework tetrahedral tilting of (ZnCo)O ₄ . The lattice volume, V , remains comparable between 626.27 Å ³ and 626.017 (7) Å ³ from x = 0 to x = 0.8. UV-visible absorption spectrum measurements indicate the band gap of these two materials to be ≈3.3 and ≈3.5 eV, respectively, therefore potential UV photocatalytic materials. Reference powder X-ray diffraction patterns of these compounds have been submitted to be included in the Powder Diffraction File (PDF).