New Chemistry Unit , Jawaharlal Nehru Centre for Advanced Scientific Research , Bengaluru 560064 , India.
Inorg Chem. 2018 Oct 15;57(20):12576-12587. doi: 10.1021/acs.inorgchem.8b01650. Epub 2018 Oct 3.
In this work, we have discovered the anisotropic near-zero thermal expansion (NZTE) behavior in a family of compounds REAg Ga ( RE = La-Nd, Sm, Eu, and Yb). The compounds adopt the CeAlGa structure type and were obtained as single crystals in high yield by metal flux growth technique using gallium as active flux. Temperature-dependent single crystal X-ray diffraction suggests that all the compounds exhibit near zero thermal expansion along c direction in the temperature range of 100-450 K. Temperature-dependent X-ray absorption near-edge spectroscopic study confirmed ZTE behavior is due to the geometrical features associated within the crystal structure. The anisotropic NZTE behavior was further established by anisotropic magnetic measurements on selected single crystals. The atomic displacement parameters, apparent bond lengths, bond angles, and structural distortion with respect to the temperature reveal that geometric features associated with the structural distortion cause the anisotropic NZTE along c-direction. The preliminary magnetic studies suggest all the compounds are paramagnetic at room temperature except LaAgGa. Electrical resistivity study reveals that compounds from this series are metallic in nature.
在这项工作中，我们发现了一系列化合物 REAg Ga（RE = La-Nd、Sm、Eu 和 Yb）中具有各向异性近零热膨胀（NZTE）的行为。这些化合物采用 CeAlGa 结构类型，通过使用镓作为活性助熔剂的金属助熔剂生长技术，以高产率获得单晶。温度相关的单晶 X 射线衍射表明，所有化合物在 100-450 K 的温度范围内沿 c 方向表现出近零热膨胀。温度相关的 X 射线吸收近边光谱研究证实，ZTE 行为是由于晶体结构内的几何特征所致。通过对选定的单晶进行各向异性磁测量，进一步证实了各向异性 NZTE 行为。原子位移参数、表观键长、键角以及结构变形与温度的关系表明，与结构变形相关的几何特征导致了沿 c 方向的各向异性 NZTE。初步的磁性研究表明，除了 LaAgGa 之外，所有化合物在室温下均为顺磁性。电阻率研究表明，该系列化合物具有金属性质。
