A d-Band Electron Correlated Thermoelectric Thermistor Established in Metastable Perovskite Family of Rare-Earth Nickelates.

The d-band electron correlations shed a light on bridging multiple functionalities within one material system, and this further extends the horizon in material designs and their emerging device applications. Herein, we demonstrate the combination of thermoelectric and thermistor functionalities within the perovskite family of correlated rare-earth nickelates (NiO) having small rare-earth elements (i.e., YNiO and DyNiO), in addition to their already known metal-to-insulator transitions. In contrast to conventional semiconductive materials, the electronic band structure of NiO split within the hybridized Ni3d-O2p is closely coupled to the structure of NiO octahedron. Based on such a distinguished feature, it is possible to achieve the coexistence of a large magnitude of thermopower () and negative temperature coefficient of resistance (NTCR) in the insulating phase of NiO with small and more distorted NiO octahedron. This establishes a thermoelectric thermistor that can be used for sensing the thermal perturbations by integrating the two distinguished detection modes within one system: the active mode utilizing the high NTCR, and the passive mode utilizing the large . It is worth noticing that as-achieved -NTCR relationship in NiO differs form the one for conventional semiconductors, in which cases enlarging the band gap enlarges but reduces NTCR. As achieved thermoelectric thermistor combing thermistor and thermoelectric functionalities via electron correlation opens up a new direction to explore emerging energy/electronic devices for sensing the thermal perturbations. The temperature range that keeps a high thermoelectric thermistor performance (i.e., |TCR | >2%K and meanwhile > 100 μVK) of NiO with a small rare-earth radius is possible to cover most of the outdoor conditions on earth (i.e., -50 to 150 °C).