Achieving negative thermal expansion in α-MoO3 by chemical substitution

Abstract

This work investigates controlling the thermal expansion of α-MoO₃ by varying compositions and concentrations. Individual W or Cr doping can affect the magnitude of thermal expansion of α-MoO₃, with Cr doping at 25 % promoting thermal expansion and W doping at 25 % slightly weakening it. Surprisingly, Fe/Co codoping can lead to different thermal behaviors of α-MoO₃, including positive thermal expansion (PTE), negative thermal expansion (NTE), and zero thermal expansion (ZTE). It is found that Fe/Co codoped α-MoO₃ exhibits ZTE at 12.5 % and NTE at 25 %, respectively. Moreover, we explore the effect of composition on the bulk modulus of α-MoO₃. It is found that Fe/Co codoped α-MoO₃ possesses atypical thermal stiffening upon heating. The electronic properties of α-MoO₃ can be regulated through doping, where Fe/Co codoping can significantly reduce the band gap. This work supplies a productive route for experimental screening and data mining in controlling the thermal expansion and other physical properties of α-MoO₃ by chemical substitution.