Niobium’s superconducting properties are affected by the presence and precipitation of impurities in the near-surface region. A systematic wide-temperature range x-ray diffraction study is presented addressing the effect of low temperatures (108 K–130K) and annealing treatments (523K in nitrogen atmosphere, 400K in UHV) on the near-surface region of a hydrogen-loaded Nb(100) single-crystal. Under these conditions, the response of the natural surface oxides (Nb₂O₅, NbO₂, and NbO) and the changes in the subsurface concentration of interstitial species in Nb are explored, thereby including the cryogenic temperature regime relevant for device operation. The formation and suppression of niobium hydrides in such conditions are also investigated. These treatments are shown to result in: (i) an increase in the concentration of interstitial species (oxygen and nitrogen) occupying the octahedral sites of the Nb bcc lattice at room temperature, both in the near-surface region and in the bulk. (ii) A decrease in the concentration of interstitials within the first 10nm from the surface at 130K. (iii) Hydride formation suppression at temperatures as low as 130K. These results show that mild annealing in nitrogen atmosphere can suppress the formation of superconducting-detrimental niobium hydrides, while subsurface interstitial atoms tend to segregate towards the surface at 130K, therefore altering the local concentration of impurities within the RF penetration depth of Nb. These processes are discussed in the context of the improvement of niobium superconducting radio-frequency cavities for next-generation particle accelerators.

铌的超导特性受到近地表区域中杂质的存在和沉淀的影响。提出了一项系统的宽温度范围 X 射线衍射研究，研究低温 (108 K–130K) 和退火处理（氮气氛中 523K，UHV 中 400K）对载氢 Nb 的近表面区域的影响(100) 单晶。在这些条件下，天然表面氧化物（Nb ₂ O ₅、NbO ₂, 和 NbO) 以及 Nb 中间隙物质的亚表面浓度的变化，从而包括与设备操作相关的低温状态。还研究了在这种条件下铌氢化物的形成和抑制。这些处理显示出：（i）在室温下，在近表面区域和整体中，占据 Nb bcc 晶格八面体位置的间隙物质（氧和氮）的浓度增加。(ii) 在 130K 时，距表面前 10nm 内的间隙浓度降低。(iii) 在低至 130K 的温度下抑制氢化物形成。这些结果表明，在氮气气氛中温和退火可以抑制对超导有害的铌氢化物的形成，而次表面间隙原子在 130K 时倾向于向表面分离，因此改变了 Nb 射频穿透深度内的局部杂质浓度。这些过程在改进用于下一代粒子加速器的铌超导射频腔的背景下进行了讨论。