Department of Applied Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan.
Institute for Advanced Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan.
Nat Commun. 2017 Jan 10;8:14102. doi: 10.1038/ncomms14102.
Large negative thermal expansion (NTE) has been discovered during the last decade in materials of various kinds, particularly materials associated with a magnetic, ferroelectric or charge-transfer phase transition. Such NTE materials have attracted considerable attention for use as thermal-expansion compensators. Here, we report the discovery of giant NTE for reduced layered ruthenate. The total volume change related to NTE reaches 6.7% in dilatometry, a value twice as large as the largest volume change reported to date. We observed a giant negative coefficient of linear thermal expansion α=-115 × 10 K over 200 K interval below 345 K. This dilatometric NTE is too large to be attributable to the crystallographic unit-cell volume variation with temperature. The highly anisotropic thermal expansion of the crystal grains might underlie giant bulk NTE via microstructural effects consuming open spaces in the sintered body on heating.
在过去的十年中，人们在各种材料中发现了大的负热膨胀（NTE），特别是与磁、铁电或电荷转移相变相关的材料。这种 NTE 材料因其可用作热膨胀补偿器而引起了相当大的关注。在这里，我们报告了减少层状钌酸盐的巨大 NTE 的发现。与 NTE 相关的总体积变化在膨胀计中达到 6.7%，是迄今为止报道的最大体积变化的两倍。我们在 345 K 以下 200 K 的温度范围内观察到了一个巨大的负线热膨胀系数 α=-115×10^-6 K，在 200 K 以下的温度范围内达到了-115×10^-6 K。这种膨胀计 NTE 太大，不能归因于晶胞体积随温度的变化。晶粒的各向异性热膨胀可能通过微结构效应在加热时消耗烧结体中的开放空间来产生巨大的体 NTE。
