Anomalous thermal and elastic properties of an epitaxial NiTi film exhibiting R-phase
Abstract
Shape memory alloys like NiTi are at the core of emerging thermal management applications, including elastocaloric refrigeration, thermoelastic harvesting, and latent heat storage. Most of these applications benefit from a small scale due to the accelerated heat exchange, but obtaining precise functional properties of films is challenging. Here we demonstrate that transient grating spectroscopy (TGS) enables characterization of elastic coefficients and thermal diffusivity of a 3 μm thick epitaxial NiTi film during a thermally induced phase transformation. The in-situ measurement of a complete austenite→R-phase→martensite→austenite temperature cycle reveals that the elastic properties exhibit a crossover of the shear moduli (from c′ < c44 in austenite to c′ > c44 in martensite) and that the thermal diffusivity changes by a factor of {4.5} between the R-phase and austenite. This dramatic change, together with the absence of hysteresis between the R-phase and austenite, makes NiTi a promising material candidate for thermal switches. The results indicate that the change in thermal diffusivity originates from an anomalous heat capacity of the R-phase. Furthermore, our TGS study provides temperature-dependent thermal and elastic properties required for simulating thermal management microsystems using this material.
Versions
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BibTeX
@misc{repcek2026anomalous,
title = {{Anomalous thermal and elastic properties of an epitaxial NiTi film exhibiting R-phase}},
author = {Kristýna Repček and Tomáš Grabec and David Mareš and Pavla Stoklasová and Petr Sedlák and Jakub Kušnír and Petr Veřtát and Oleg Heczko and Sebastian Fähler and Klara Lünser and H. Seiner},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2605.17553},
eprint = {2605.17553},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2605.17553},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Anomalous thermal and elastic properties of an epitaxial NiTi film exhibiting R-phase
AU - Kristýna Repček
AU - Tomáš Grabec
AU - David Mareš
AU - Pavla Stoklasová
AU - Petr Sedlák
AU - Jakub Kušnír
AU - Petr Veřtát
AU - Oleg Heczko
AU - Sebastian Fähler
AU - Klara Lünser
AU - H. Seiner
PY - 2026
DA - 2026/11/05
PB - arXiv
DO - 10.48550/arxiv.2605.17553
UR - https://arxiv.org/abs/2605.17553
AB - Shape memory alloys like NiTi are at the core of emerging thermal management applications, including elastocaloric refrigeration, thermoelastic harvesting, and latent heat storage. Most of these applications benefit from a small scale due to the accelerated heat exchange, but obtaining precise functional properties of films is challenging. Here we demonstrate that transient grating spectroscopy (TGS) enables characterization of elastic coefficients and thermal diffusivity of a 3 μm thick epitaxial NiTi film during a thermally induced phase transformation. The in-situ measurement of a complete austenite→R-phase→martensite→austenite temperature cycle reveals that the elastic properties exhibit a crossover of the shear moduli (from c^′ < c_44 in austenite to c^′ > c_44 in martensite) and that the thermal diffusivity changes by a factor of {4.5} between the R-phase and austenite. This dramatic change, together with the absence of hysteresis between the R-phase and austenite, makes NiTi a promising material candidate for thermal switches. The results indicate that the change in thermal diffusivity originates from an anomalous heat capacity of the R-phase. Furthermore, our TGS study provides temperature-dependent thermal and elastic properties required for simulating thermal management microsystems using this material.
ER -