Thermoelectric performance and humidity sensing characteristics of La₂CuO₄ nanofibers

Thermoelectric and humidity sensing characteristics of single phase La₂CuO₄ (LCO) nanofibers were investigated. LCO nanofibers-based devices were fabricated and characterized for their possible use in thermoelectric and humidity sensing applications. The Seebeck coefficient (S) of the fabricated device increased linearly from ∼30 (at 298 K) to 300 μV/K (at 308 K); however, the per degree rise in S (∼25 μV/K), suggested a high S at high temperatures. Thermal conductivity of these nanofibers is expected to be lower than that of the bulk counterparts due to their one dimensional nanostructure comprising nano-size grains connected via grain boundaries and high surface to volume ratio. Impedance analysis of LCO nanofibers-based humidity sensors exhibited a narrow absorption-desorption hysteresis and a fast response-recovery time (∼4 s) in the relative humidity range of 50-98%. The observed short c time, impedance repeatability, stability and sensitivity of LCO nanofibers make these nanofibers suitable for applications in humidity sensing. A protonic model was proposed for the sensing mechanism of LCO sensors wherein the dominant charge carriers (probably protons) tunnel via hopping from one active site to another through hydrogen bonding following the Grotthuss mechanism.