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用X射线衍射照相、X射线衍射仪及透射电子显微镜分析了用液相淬火技术制备的La_(30)Al_(20)合金样品,结果表明样品是非晶态结构。差热分析(DTA)结果表明,非晶态样品的晶化温度T_(cr)为280℃左右,玻璃温度T_g为242℃左右。非晶态样品低温高压(流体静压法)试验结果表明:压力从0至4.77kbar,T_c从3.87K提高到4.18K。高压下,超导前的剩余电阻与常压下相比较有明显下降。非晶态样品经高温高压(25kbar,～160℃,40min)处理后,X射线衍射仪分析结果表明:发生了由非晶态→晶态的结构相变。相变产物由平衡相α-La和新的亚稳过渡相组成。其T_c从～3.9K提高到5.7K,该亚稳相结构与化学成分尚不清楚。本文并对所获得的实验结果进行了讨论。
The samples of La_ (30) Al_ (20) alloy prepared by liquid quenching technique were analyzed by X-ray diffraction, X-ray diffraction and transmission electron microscopy. The results showed that the samples were amorphous. The results of differential thermal analysis (DTA) show that the crystallization temperature T cr of the amorphous sample is about 280 ℃ and the glass temperature T_g is about 242 ℃. The results of the low temperature and high pressure (hydrostatic method) test of amorphous samples show that the pressure increases from 0 to 4.77kbar and Tc increases from 3.87K to 4.18K. Under high pressure, the residual resistance before superconducting is significantly lower than that under atmospheric pressure. After the amorphous samples were treated by high temperature and high pressure (25kbar, ~ 160 ℃, 40min), the results of X-ray diffractometer showed that the phase transition from amorphous to crystalline state occurred. The phase transition product consists of the equilibrium phase α-La and a new metastable transition phase. The Tc increases from ~ 3.9K to 5.7K, and the structure and chemical composition of the metastable phase are not clear. In this paper, the experimental results obtained are discussed.