Tuning the electronic conductance of REHx (RE=Nd, Ce, Pr) by structural deformation

Hydride ion (H−) conductors have drawn much attention due to their potential applications in hydride-ion-based devices. Rare earth metal hydrides (REHx) have fast H− conduction which, unfortunately, is accompanied by detrimental electron conduction preventing their application as ion conductors. Here, REHx (RE = Nd, Ce, and Pr) with varied grain sizes, rich grain boundaries, and defects have been prepared by ball milling and subsequent sintering. The electronic conductivity of the ball-milled REHx samples can be reduced by 2–4 orders of magnitude compared with the non-ball-milled samples. The relationship of electron conduction and miscrostructures in REHx is studied and discussed based on experimental data and previously-proposed classical and quantum theories. The H− conductivity of all REHx is about 10−4 to 10−3 S cm−1 at room temperature, showing promise for the development of H− conductors and their applications in clean energy storage and conversion.