Jiangxi Key Laboratory for Rare Earth Magnetic Materials and Devices/Institute for Rare Earth Magnetic Materials and Devices (IREMMD) , Jiangxi University of Science and Technology , Ganzhou 341000 , People's Republic of China.
Canadian Light Source , University of Saskatchewan , Saskatoon , Saskatchewan S7N 2V3 , Canada.
Inorg Chem. 2018 Nov 19;57(22):14199-14207. doi: 10.1021/acs.inorgchem.8b02195. Epub 2018 Nov 7.
Negative thermal expansion (NTE) material as a compensator is very important for accurately controlling the thermal expansion of materials. Along with the magnitude of the coefficient of thermal expansion, the operating temperature window of the NTE materials is also a major concern. However, only a few of the NTE materials possess both a large operating temperature range and a large thermal expansion coefficient. To explore this type of new NTE material, the MnCoGe fine powders were prepared by mechanical ball milling (BM). These fine powders show a largely extended NTE operation temperature window simultaneously possessing a giant thermal expansion coefficient. For samples treated with different BM times, such as the BM-0.5h, BM-4h, and BM-12 h samples, the operating temperature window (Δ T) and linear thermal expansion coefficient (α) are 167 K (222-389 K) and ∼ -63 ppm/K, 221 K (140-360 K) and ∼ -41.3 ppm/K, and 208 K (234-442 K) and ∼ -40 ppm/K, respectively, which are larger than most well-known NTE materials. More strikingly, all BM samples have a large constant linear NTE coefficient with an ultrawide temperature window covering room temperature. For these three samples, these values are ∼ -52 ppm/K (140 K), ∼ -58.3 ppm/K (110 K), and ∼ -65 ppm/K (80 K), respectively. The origin of the excellent NTE properties is discussed based on the thermomagnetic measurements and X-ray absorption spectroscopic results.
负热膨胀（NTE）材料作为补偿剂对于准确控制材料的热膨胀非常重要。除了热膨胀系数的大小外，NTE 材料的工作温度窗口也是一个主要关注点。然而，只有少数 NTE 材料同时具有较大的工作温度范围和较大的热膨胀系数。为了探索这种新型 NTE 材料，采用机械球磨（BM）法制备了 MnCoGe 细粉。这些细粉表现出很大程度上扩展的 NTE 工作温度窗口，同时具有巨大的热膨胀系数。对于经过不同 BM 时间处理的样品，例如 BM-0.5h、BM-4h 和 BM-12h 样品，工作温度窗口（ΔT）和线性热膨胀系数（α）分别为 167 K（222-389 K）和 ∼ -63 ppm/K、221 K（140-360 K）和 ∼ -41.3 ppm/K、以及 208 K（234-442 K）和 ∼ -40 ppm/K，均大于大多数知名的 NTE 材料。更引人注目的是，所有 BM 样品都具有很大的恒定线性 NTE 系数，超宽温度窗口覆盖室温。对于这三个样品，这些值分别为 ∼ -52 ppm/K（140 K）、 ∼ -58.3 ppm/K（110 K）和 ∼ -65 ppm/K（80 K）。根据热磁测量和 X 射线吸收光谱结果讨论了优异的 NTE 性能的起源。
