β-Phase YbSbH: Magnetic and Thermoelectric Properties Traversing from an Electride to a Semiconductor.

An electride is a compound that contains a localized electron in an empty crystallographic site. This class of materials has a wide range of applications, including superconductivity, batteries, photonics, and catalysis. Both polymorphs of YbSb (the orthorhombic CaSbF structure type (β phase) and hexagonal MnSi structure type (α phase)) are known to be electrides with electrons localized in 0D tetrahedral cavities and 1D octahedral chains, respectively. In the case of the orthorhombic β phase, an interstitial H can occupy the 0D tetrahedral cavity, accepting the anionic electron that would otherwise occupy the site, providing the formula of YbSbH. DFT computations show that the hexagonal structure is energetically favored without hydrogen and that the orthorhombic structure is more stable with hydrogen. Polycrystalline samples of orthorhombic β phase YbSbH ( = 0.25, 0.50, 0.75, 1.0) were synthesized, and both PXRD lattice parameters and H MAS NMR were used to characterize H composition. Magnetic and electronic transport properties were measured to characterize the transition from the electride (semimetal) to the semiconductor. Magnetic susceptibility measurements indicate a magnetic moment that can be interpreted as resulting from either the localized antiferromagnetically coupled electride or the presence of a small amount of Yb. At lower H content ( = 0.25, 0.50), a low charge carrier mobility consistent with localized electride states is observed. In contrast, at higher H content ( = 0.75, 1.0), a high charge carrier mobility is consistent with free electrons in a semiconductor. All compositions show low thermal conductivity, suggesting a potentially promising thermoelectric material if charge carrier concentration can be fine-tuned. This work provides an understanding of the structure and electronic properties of the electride and semiconductor, YbSbH, and opens the door to the interstitial design of electrides to tune thermoelectric properties.