Control of Thermal Expansion in TaVO₅ by Double Chemical Substitution

The control of thermal expansion is an important andchallengingissue. Focusing attention on the class of AMO(5) negativethermal expansion (NTE) materials, an approach to control their thermalexpansion is still missing. In this work, the thermal expansion ofTaVO(5) has been controlled from strong negative to zeroto positive by double chemical substitution, i.e., Ti and Mo replaceTa and V elements, respectively. A joint study of temperature-dependentX-ray diffraction, X-ray photoelectron spectroscopy, and first-principlescalculations has been performed to investigate the thermal expansionmechanism. With the increasing substitution of Ti and Mo atoms, thevalence state always remains balanced, and the volume decreases togetherwith a lattice distortion, which leads to the suppression of the NTE.Lattice dynamics calculations confirm that the negative Gru''neisenparameters of the low-frequency modes weaken and the thermal vibrationsof the polyhedral units diminish after the substitution of Ti andMo atoms. The present work successfully achieves a tailored thermalexpansion in TaVO5 and draws a possible way to controlthe thermal expansion of other NTE materials. We adopt the double-element chemicalsubstitution to realizethe control of thermal expansion from strong negative to zero to positivein a TaVO5 system, which causes more lattice distortionby simultaneously part replacing the A site (octahedron) and M site(tetrahedron).