Intrinsic thermal expansion and tunability of thermal expansion coefficient in Ni-substituted Co ₂ V ₂ O ₇

Journal Article · Fri Oct 06 00:00:00 EDT 2023 · JPhys Materials

DOI:https://doi.org/10.1088/2515-7639/acfdce· OSTI ID:2008000

Esteban, Erica T. B.; Garcia, Jasmine J.; Windover, Sophie R. ; Cooley, Joya A.

Abstract Framework oxide materials are well-known for exhibiting not only negative thermal expansion (NTE), but also demonstrating thermal expansion that can be controlled using composition as a tuning parameter. In this work, we study the intrinsic thermal expansion properties of Co ₂ V ₂ O ₇ , which has shown bulk linear NTE, and attempt to understand how substituting Ni ²⁺ for Co ²⁺ will affect the thermal expansion. The isomorphic solid solution is synthesized through solid-state methods and characterized using x-ray diffraction (XRD), diffuse reflectance spectroscopy, and neutron diffraction. The size difference between Ni ²⁺ and Co ²⁺ as well as the polyhedral volume of each Co ²⁺ metal coordination environment in the crystal structure allows Ni ²⁺ to partially be directed toward one crystallographic site over the other. Variable temperature synchrotron XRD data are employed to understand intrinsic thermal expansion. Across the solid solution, no intrinsic NTE is observed at the microscopic level, yet a degree of tunability in the thermal expansion coefficient with Ni substitution is demonstrated. The disparities between the intrinsic and bulk thermal expansion properties suggest that a morphological mechanism may have resulted in NTE in the bulk.

• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC02-06CH11357; AC02-76SF00515
• OSTI ID: 2008000
• Alternate ID(s): OSTI ID: 2006695
• Journal Information: JPhys Materials, Journal Name: JPhys Materials Vol. 6 Journal Issue: 4; ISSN 2515-7639
• Publisher: IOP Publishing
• Country of Publication: United Kingdom
• Language: English