Microstructural and transport properties of Mg doped CuFeO2 thin films: A promising material for high accuracy miniaturized temperature sensors based on the Seebeck effect

Delafossite type Mg doped CuFeO2 thin films have been deposited on fused silica by radio-frequency magnetron sputtering. As-deposited 300 nm thick films have been obtained and post-annealed between 350 and 750 °C under primary vacuum. The delafossite structure appears for the samples annealed above 550 °C. The microstructural analysis showed the presence of cracks and an inhomogeneous distribution of the dopant in the thickness. Only the sample annealed at 700 °C showed CuFeO2 stable phases, lower impurities amount, a high and constant Seebeck coefficient (+416 ±3 μV K−1) and good electrical conductivity (1.08 S cm−1 at 25 °C). High accuracy temperature sensors based on the Seebeck effect not only need high Seebeck coefficient without any drift with the temperature, but also a sufficient electrical conductivity and high phase stability. Thanks to its properties and also its low thermal conductivity (4.8 ±0.6 W m−1K−1 at 25 °C) due to the thin film configuration and the polaronic transport, the Mg doped CuFeO2 thin film annealed at 700 °C was found to be a very good p-type material for high accuracy miniaturized temperature measurement sensors based on the Seebeck effect in the medium temperature range. •Mg doped CuFeO2 thin films was deposited by RF magnetron sputtering then annealed at various temperature under vacuum.•Mg doped CuFeO2 delafossite phase was obtained after annealing.•Optimized Mg doped CuFeO2 thin film showed high Seebeck coefficient without any drift.•Thermal conductivity of Mg doped CuFeO2 thin film was measured.•CuFeO2:Mg thin films was found to be a promising material well adapted for high accuracy miniaturized temperature sensors.