Imperial College London
Alternate

ProfessorArashMostofi

Faculty of Engineering, Department of Materials

Professor of Theory and Simulation of Materials
 
 
 
//

Contact

 

+44 (0)20 7594 8154a.mostofi Website

 
 
//

Location

 

Bessemer B332Royal School of MinesSouth Kensington Campus

//

Summary

 

Publications

Citation

BibTex format

@article{Ablitt:2019:10.1021/acs.chemmater.9b04512,
author = {Ablitt, C and McCay, H and Craddock, S and Cooper, L and Reynolds, E and Mostofi, AA and Bristowe, N and Murray, CA and Senn, M},
doi = {10.1021/acs.chemmater.9b04512},
journal = {Chemistry of Materials},
pages = {605--610},
title = {Tolerance factor control of uniaxial negative thermal expansion in a layered perovskite},
url = {http://dx.doi.org/10.1021/acs.chemmater.9b04512},
volume = {32},
year = {2019}
}
Download

RIS format (EndNote, RefMan)

TY  - JOUR
AB  - By tuning the tolerance factor, $t$, of the Ruddlesden--Popper oxide Ca$_2$MnO$_4$ through isovalent substitutions we show that the uniaxial coefficient of linear thermal expansion (CLTE) of these systems can be systematically changed through large negative to positive values. High-resolution X-ray diffraction measurements show that the magnitude of uniaxial negative thermal expansion (NTE) increases as $t$ decreases across the stability window of the NTE phase. Transitions to phases with positive thermal expansion (PTE) are found to occur at both the high-$t$ and low-$t$ limits of stability. First-principles calculations demonstrate that reducing $t$ enhances the contribution to thermal expansion from the lowest frequency phonons, which have the character of octahedral tilts and have negative mode Gr\"uneisen parameter components along the NTE axis. By tuning $t$ to the lower edge of the NTE phase stability window, we are hence able to maximise the amplitudes of these vibrations and thereby maximise NTE with a CLTE of -8.1~ppm/K at 125~K. We also illustrate, at the other end of the phase diagram, that an enhancement in compliance of these materials associated with the rotational instability provides another mechanism by which NTE could be yet further enhanced in this and related systems.
AU  - Ablitt,C
AU  - McCay,H
AU  - Craddock,S
AU  - Cooper,L
AU  - Reynolds,E
AU  - Mostofi,AA
AU  - Bristowe,N
AU  - Murray,CA
AU  - Senn,M
DO  - 10.1021/acs.chemmater.9b04512
EP  - 610
PY  - 2019///
SN  - 0897-4756
SP  - 605
TI  - Tolerance factor control of uniaxial negative thermal expansion in a layered perovskite
T2  - Chemistry of Materials
UR  - http://dx.doi.org/10.1021/acs.chemmater.9b04512
UR  - https://pubs.acs.org/doi/10.1021/acs.chemmater.9b04512
UR  - http://hdl.handle.net/10044/1/75751
VL  - 32
ER  -
Download