Realization of ultra-low thermal expansion over a broad temperature interval in Gdx(Dy0.5Ho0.5)1-xCo2 compounds

Abstract Zero thermal expansion (ZTE) materials, particularly metals, have important applications in precision manufacturing. Here, ultra-low thermal expansion over a significantly broadened temperature interval is realized by tuning Gd content in ferrimagnetic(FIM) Gdx(Dy0.5Ho0.5)1-xCo2 compounds. The achieved coefficients of thermal expansion αl ~+1.3 × 10−6K−1 (5-220K), -1.5 × 10−6K−1 (220-280K) for x=0.5 are even better than the well-known ZTE Invar alloy Fe0.65Ni0.35, while the operation temperature interval is much wider. The origin is closely related to the regulation of magnetostrictive process by rare earth ions along c-axis in the rhombohedral FIM structure. Our work highlights the advantageous ways to generate ultra-low thermal expansion in magnetocaloric materials.