Crystal structure and charge order below the metal-insulator transition in the vanadium bronze $\beta$-SrV$_6$O$_{15}$

TL;DR

This study reveals the crystal structure and charge ordering phenomena in the vanadium bronze $eta$-SrV$_6$O$_{15}$ across its metal-insulator transition at 170 K using single crystal X-ray diffraction.

Contribution

It provides detailed structural insights into the charge order and phase transition mechanism in $eta$-SrV$_6$O$_{15}$, highlighting the preservation of space group and formation of charge clusters.

Findings

Confirmation of zigzag Sr order above 170 K

Charge order appears below 170 K with increased b-axis

Charge may form clusters of V$^{4+}$ along 1D direction

Abstract

Single crystal X-ray diffraction measurements were performed on one-dimensional mixed valence vanadium bronze $\beta$-SrV$_6$O$_{15}$ in which a metal-insulator transition exists at 170 K. Above 170 K the P2$_1$/a structure with zigzag order of Sr in the tunnels of vanadium is confirmed. In the structure below 170 K, the P2$_1$/a space group is retained with a b-axis threefold increase and a charge order appears. A Bond Valence Sum analysis shows that the charge order may consist in clusters of V$^{4+}$ regularly spaced along 1D direction.