Deviations From Vegard'S Law And Intense Raman Scattering In Low-Doped Bi2mo1-Xwxo6 (X=0-10%) Ceramics

Hume-Rothery rules along with Vegard's law form the basis of systematic doping variation resulting into similar changes in unit cell parameters and volume. Many recent reports have highlighted positive-negative departure from Vegard's law in binary semiconducting systems and a few oxide alloys as well. The current work targets investigations on the missing response of bismuth molybdate on low tungsten doping onto molybdenum sites (Bi2Mo1-xWxO6). Bismuth molybdate and bismuth tungstate have been widely reported for lattice oxygen migration-driven photocatalytic response and pressure-sensitive Raman scattering. Octahedral tilting in low-tungsten-doped Bi2Mo0.94W0.06O6 carries an interesting lattice oxygen folding toward a-c plane. As a result, unit cell polarity increases drastically and becomes a source for intense Raman scattering phase that is normally observable at pressures around 8.3 GPa. An interesting departure from Vegard's law behavior at around 5-6% tungsten doping confirms nearly identical unit cell structure rather than mix unit cell-based alloy formation.