Tailoring Negative Thermal Expansion via Tunable Induced Strain in La-Fe-Si-Based Multifunctional Material

Area of Science:

• Materials Science
• Condensed Matter Physics

Background:

• Zero thermal expansion (ZTE) composites are crucial for high-precision applications.
• La(Fe,Si)13 compounds exhibit significant negative thermal expansion (NTE) near room temperature.
• First-order phase transitions in these materials cause abrupt volume changes, limiting their use as thermal expansion compensators.

Purpose of the Study:

• To control and optimize the NTE properties of LaFeSi alloys for practical ZTE applications.
• To investigate the role of particle size, crystallite size, and induced strain on the phase transition behavior.
• To broaden the operational temperature window of NTE for improved thermal management.

Main Methods:

• Ball-milling was employed to reduce particle and crystallite sizes and introduce strain in LaFe11.9Mn0.27Si1.29Hx alloys.
• Characterization of the effects of size and strain tuning on the material's phase transition and thermal expansion properties.

Main Results:

• Ball-milling successfully decreased particle and crystallite sizes and increased lattice strain.
• The NTE operational temperature window was significantly expanded.
• The peak NTE was suppressed by up to 85%, and the transition broadened.

Conclusions:

• Induced strain is the primary mechanism governing the phase transitions in these materials.
• Optimizing strain through methods like ball-milling allows for the tuning of thermal expansion properties.
• This approach enables the development of advanced materials for room-temperature ZTE applications.