Unveiling the crystallographic origin of mechanochemically induced monoclinic to triclinic phase transformation in WO

• Published in: CrystEngComm 2021-03, Vol.23 (8), p.1821-1827
• Main Authors: Bandi, Suresh, Srivastav, Ajeet K
• Format: Article
• ISSN: 1466-8033
• DOI: 10.1039/d0ce01813a

This study reports the anomalously stabilized low-temperature triclinic phase (δ-WO 3 ) during high energy ball milling (HEBM) of the monoclinic γ-WO 3 phase. The transformation evidenced unit cell contraction with distorted structural parameters resulted in a lower symmetry phase. The phase transformation was understood to be HEBM-induced pressure/compression involved atomic displacement and octahedral tilting-driven polymorphic transition. The major distortion/cooperative octahedral tilting occurred on the (020) plane of γ-WO 3 parallel to the b axis. The crystallographic origin of such distortions and unit cell compression mechanisms are explained further. The obtained δ-WO 3 phase was stable at room temperature owing to its nanocrystalline structure (11 ± 6 nm) that limits reversible and forward transformations of δ-WO 3 → γ-WO 3 and γ-WO 3 → -WO 3 , respectively. This study reports the anomalously stabilized low-temperature triclinic phase (δ-WO 3 ) during high energy ball milling (HEBM) of the monoclinic γ-WO 3 phase.