Giant isotropic negative thermal expansion in Y-doped samarium monosulfides by intra-atomic charge transfer

Koshi Takenaka,Yosuke Mizuno,Yasutaka Imanaka,Hiroyuki S Suzuki,Daigo Asai,Naoyuki Katayama,Yasunori Yokoyama,Ryoichi Kaizu,Yoshihiko Okamoto

doi:10.1038/s41598-018-36568-w

Koshi Takenaka, Yosuke Mizuno + Show 7 more

Open Access

https://doi.org/10.1038/s41598-018-36568-w

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Abstract

Stimulated by strong demand for thermal expansion control from advanced modern industries, various giant negative thermal expansion (NTE) materials have been developed during the last decade. Nevertheless, most such materials exhibit anisotropic thermal expansion in the crystal lattice. Therefore, strains and cracks induced during repeated thermal cycling degrade their performance as thermal-expansion compensators. Here we achieved giant isotropic NTE with volume change exceeding 3%, up to 4.1%, via control of the electronic configuration in Sm atoms of SmS, (4 f)6 or (4 f)5(5d)1, by partial replacement of Sm with Y. Contrary to NTE originating from cooperative phenomena such as magnetism, the present NTE attributable to the intra-atomic phenomenon avoids the size effect of NTE and therefore provides us with fine-grained thermal-expansion compensators, which are strongly desired to control thermal expansion of microregions such as underfill of a three-dimensional integrated circuit. Volume control of lanthanide monosulfides via tuning of the 4 f electronic configuration presents avenues for novel mechanical functions of a material, such as a volume-change driven actuator by an electrical field, which has a different drive principle from those of conventional strain-driven actuators such as piezostrictive or magnetostrictive materials.

Highlights

Successive discoveries of giant negative thermal expansion (NTE) materials during the last decade are causing a paradigm shift in the field of thermal expansion control[1,2]
These giant NTE materials enable us to compensate the thermal expansion of plastics[18,19,20,21], which has been difficult to date
A promising candidate is samarium monosulfide SmS, which exhibits large volume change exceeding 7% according to the 4 f electronic configuration in the Sm atom[22]

Summary

Introduction

Successive discoveries of giant negative thermal expansion (NTE) materials during the last decade are causing a paradigm shift in the field of thermal expansion control[1,2]. High NTE of α = −115 × 10−6 K−1 and total volume change ΔV/V = 6.7% are realized in layered ruthenium oxides by the microstructural effects of a sintered body[17]. These giant NTE materials enable us to compensate the thermal expansion of plastics[18,19,20,21], which has been difficult to date. The technology of thermal expansion control is being innovated These “phase-transition-type” giant NTE materials are mostly anisotropic. Strains and defects are induced in the materials during repeated thermal cycling, thereby degrading the reproducibility of NTE functions and mechanical strength. This report presents discussion of the rich potential possessed by the intra-atomic charge transfer, which is proposed as a volume-control principle for novel mechanical functions of materials

Methods

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Conclusion