Abstract

Thermal conductivity switching in Pd-catalyzed Gd hydride films was investigated using in situ analyses of electrical, optical, structural, and thermophysical properties upon gasochromic hydrogenation/dehydrogenation at room temperature. These reactions allow the films to reversibly switch between the metallic (GdH₂) phase in the hydrogenated state and the semiconductor (GdH₃) phase in the dehydrogenated state. We fabricated three-layered films comprising Pd (5 nm)/Gd or GdH₂ (300 nm)/Mo (100 nm) using DC magnetron sputtering using Pd, Gd, and Mo targets, respectively, on unheated synthetic quartz substrates. Ar or mixture of Ar + H₂ (H₂: 5 % to 50 %) gases were used for the deposition of the Gd or GdH₂ films, respectively. The thermal conductivities of the Gd or GdH₂ films were analyzed using in situ rear-heating/rear-detection type time-domain picosecond pulsed light heating thermoreflectance measurements by employing a gas mixture of N₂/Ar and H₂ (H₂: 3 %) at 1 atm, which is below the explosive limit for hydrogen. The thermal conductivities of Gd and GdH₂ films were measured for one and two hydro-/dehydrogenation cycles, respectively. The thermal switching ratios of the ON state thermal conductivity to the OFF state thermal conductivity were 6.4 and 2.9–5.4 for the Gd film and the GdH₂ (H₂: 5 %–50 %) films, respectively. The thermal conductivity of the Gd hydrides films changed along with those estimated from the Wiedemann–Franz Law and electrical conductivities.

中文翻译：

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Pd 催化 Gd 和 GdH2 薄膜在气致变色氢化和脱氢过程中的热导率转变

摘要

通过对室温气致变色氢化/脱氢时的电学、光学、结构和热物理性质进行原位分析，研究了 Pd 催化的氢化钆薄膜的热导率转换。这些反应使得薄膜能够在氢化状态的金属(GdH ₂ )相和脱氢状态的半导体(GdH ₃ )相之间可逆地转换。我们分别使用 Pd、Gd 和 Mo 靶材在未加热的合成石英基板上使用直流磁控溅射技术制备了包含 Pd (5 nm)/Gd 或 GdH ₂ (300 nm)/Mo (100 nm)的三层薄膜。Ar或Ar+H ₂ (H ₂：5％至50％)气体的混合物分别用于沉积Gd或GdH ₂膜。采用原位后加热/后检测型时域皮秒脉冲光加热热反射测量，采用 N 2 _{/ Ar}和 H ₂ (H ₂ : 3 %）在 1 个大气压下，低于氢气的爆炸极限。分别测量一次和两次加氢/脱氢循环的Gd和GdH ₂膜的热导率。Gd薄膜和GdH ₂ (H ₂ : 5 %–50 %)薄膜的ON状态热导率与OFF状态热导率的热切换比分别为6.4和2.9-5.4。Gd 氢化物薄膜的热导率随着 Wiedemann-Franz 定律和电导率估计值的变化而变化。