TY - JOUR
T1 - High-Performance Thermomagnetic Generators Based on Heusler Alloy Films
AU - Gueltig, Marcel
AU - Wendler, Frank
AU - Ossmer, Hinnerk
AU - Ohtsuka, Makoto
AU - Miki, Hiroyuki
AU - Takagi, Toshiyuki
AU - Kohl, Manfred
PY - 2017/3/8
Y1 - 2017/3/8
N2 - Recent developments on Heusler alloys including Ni–Mn–X and Ni–Co–Mn–X (X = Ga, In, Sn,…) demonstrate multiferroic phase transformations with large abrupt changes in lattice parameters of several percent and corresponding abrupt changes in ferromagnetic ordering near the transition temperatures. These materials enable a new generation of thermomagnetic generators that convert heat to electricity within a small temperature difference below 5 K. While thermodynamic calculations on this energy conversion method predict a power density normalized to material volume of up to 300 mW cm−3, experimental results have been in the range of µW cm−3. Challenges are related to the development of materials with bulk-like single-crystal properties as well as geometries with large surface-to-volume ratio for rapid heat exchange. This study demonstrates efficient thermomagnetic generation via resonant actuation of freely movable thin-film devices of the Heusler alloy Ni–Mn–Ga with unprecedented power density of 118 mW cm−3 that compares favorably with the best thermoelectric generators. Due to the large temperature-dependent change of magnetization of the films, a periodic temperature change of only 3 K is required for operation. The duration of thermomagnetic duty cycle is only about 12 ms, which matches with the period of oscillatory motion.
AB - Recent developments on Heusler alloys including Ni–Mn–X and Ni–Co–Mn–X (X = Ga, In, Sn,…) demonstrate multiferroic phase transformations with large abrupt changes in lattice parameters of several percent and corresponding abrupt changes in ferromagnetic ordering near the transition temperatures. These materials enable a new generation of thermomagnetic generators that convert heat to electricity within a small temperature difference below 5 K. While thermodynamic calculations on this energy conversion method predict a power density normalized to material volume of up to 300 mW cm−3, experimental results have been in the range of µW cm−3. Challenges are related to the development of materials with bulk-like single-crystal properties as well as geometries with large surface-to-volume ratio for rapid heat exchange. This study demonstrates efficient thermomagnetic generation via resonant actuation of freely movable thin-film devices of the Heusler alloy Ni–Mn–Ga with unprecedented power density of 118 mW cm−3 that compares favorably with the best thermoelectric generators. Due to the large temperature-dependent change of magnetization of the films, a periodic temperature change of only 3 K is required for operation. The duration of thermomagnetic duty cycle is only about 12 ms, which matches with the period of oscillatory motion.
KW - actuators
KW - energy harvesting
KW - magnetic films
KW - martensitic transformation
KW - shape memory films
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U2 - 10.1002/aenm.201601879
DO - 10.1002/aenm.201601879
M3 - Article
AN - SCOPUS:85004065414
VL - 7
JO - Advanced Energy Materials
JF - Advanced Energy Materials
SN - 1614-6832
IS - 5
ER -