Properties of polyamorphous ${\text{Ce}}_{75}{\text{Al}}_{25}$ metallic glasses

The thermal stability and electronic transport properties of polyamorphous ${\text{Ce}}_{75}{\text{Al}}_{25}$ metallic glass (MG) have been investigated using in situ high-pressure, high-temperature, energy-dispersive synchrotron x-ray diffraction and in situ high-pressure and low-temperature, four-probe resistance measurements. The results are compared with the properties of ${\text{La}}_{75}{\text{Al}}_{25}$ MG. The pressure dependence of the crystallization temperature and resistance of the ${\text{Ce}}_{75}{\text{Al}}_{25}$ MG exhibited turning points at the polyamorphic transition pressure, 1.5 GPa, and they clearly presented different behaviors below and above 1.5 GPa. In contrast, no turning points were observed in the ${\text{La}}_{75}{\text{Al}}_{25}$ MG (La has no $4f$ electron). Additionally, the pressure-tuned temperature coefficient of resistance of the ${\text{Ce}}_{75}{\text{Al}}_{25}$ MG was observed. These results revealed switchable properties in the polyamorphous ${\text{Ce}}_{75}{\text{Al}}_{25}$ MG that are linked with $4f$ electron delocalization.

Figure 1

(Color online) In situ HPHT-EDXRD patterns from ${\text{Ce}}_{75}{\text{Al}}_{25}$ MG, recorded at various temperatures under (a) 1.1 GPa and (b) 3.0 GPa and from ${\text{La}}_{75}{\text{Al}}_{25}$ MG under (c) 0.3 GPa. The crystallization phases for each sample are identical over the entire pressure range studied, and their diffraction peaks are marked by hcp ${\text{Ce}}_3\text{Al}$ in (a) and (b) and cubic ${\text{La}}_3\text{Al}$ in (c). Some other diffraction peaks for boron nitride, originating from the sample holder, are marked by BN, and four fluorescence peaks from Ce or La also are marked.

Figure 2

(Color online) Crystallization onset temperatures $T_x$ of ${\text{Ce}}_{75}{\text{Al}}_{25}$ and ${\text{La}}_{75}{\text{Al}}_{25}$ MGs as functions of pressure. The data at ambient pressure were estimated from the DSC measurements and are marked by red solid stars.

Figure 3

(Color online) (a) Resistances of ${\text{Ce}}_{75}{\text{Al}}_{25}$ and ${\text{La}}_{75}{\text{Al}}_{25}$ MGs as functions of pressure at ambient temperature. (b) The temperature dependences of the resistance of ${\text{Ce}}_{75}{\text{Al}}_{25}$ MG at ambient pressure, 1.5 and 12 GPa.