Wang Bi-Xia, Zheng Hong, Krivyakina E, Chmaissem O, Lopes Pietro Papa, Lynn J W, Gallington Leighanne C, Ren Y, Rosenkranz S, Mitchell J F, Phelan D
Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA.
Department of Physics, Northern Illinois University, DeKalb, Illinois 60115, USA.
Phys Rev Mater. 2020 Aug;4(8). doi: 10.1103/PhysRevMaterials.4.084409.
The recent reports of superconductivity in Nd Sr NiO/SrTiO heterostructures have reinvigorated interest in potential superconductivity of low-oxidation state nickelates. Synthesis of Ni-containing compounds is notoriously difficult. In the current work, a combined sol-gel combustion and high-pressure annealing technique was employed to prepare polycrystalline perovskite Nd Sr NiO ( = 0, 0.1, and 0.2). Metal nitrates and metal acetates were used as starting materials, and the latter were found to be superior to the former in terms of safety and reactivity. The Nd Sr NiO compounds were subsequently reduced to Nd Sr NiO using calcium hydride in a sealed, evacuated quartz tube. To understand the synthesis pathway, the evolution from NdNiO to NdNiO was monitored using synchrotron x-ray diffraction during the reduction process. Electrical transport properties were consistent with an insulator-metal transition occurring between = 0 and 0.1 for Nd Sr NiO. Superconductivity was not observed in our bulk samples of Nd Sr NiO. Neutron diffraction experiments at 3 and 300 K were performed on NdSrNiO, in which no magnetic Bragg reflections were observed, and the results of structural Rietveld refinement are provided.
近期关于钕锶镍氧化物/钛酸锶异质结构中超导电性的报道，重新激发了人们对低氧化态镍酸盐潜在超导电性的兴趣。众所周知，含镍化合物的合成非常困难。在当前工作中，采用溶胶 - 凝胶燃烧和高压退火相结合的技术制备了多晶钙钛矿钕锶镍氧化物（= 0、0.1和0.2）。金属硝酸盐和金属醋酸盐用作起始原料，发现后者在安全性和反应活性方面优于前者。随后，在密封的抽空石英管中使用氢化钙将钕锶镍氧化物化合物还原为钕锶镍氧化物。为了解合成途径，在还原过程中使用同步加速器X射线衍射监测从钕镍氧化物到钕镍氧化物的演变。对于钕锶镍氧化物，电输运性质与在= 0和0.1之间发生的绝缘体 - 金属转变一致。在我们的钕锶镍氧化物块状样品中未观察到超导电性。对钕锶镍氧化物进行了3 K和300 K下中子衍射实验，其中未观察到磁性布拉格反射，并提供了结构Rietveld精修结果。
