Proof-of-concept thermoelectric oxygen sensor exploiting oxygen mobility of GdBaCo2O5+{\delta}

TL;DR

This study demonstrates a proof-of-concept thermoelectric oxygen sensor using GdBaCo2O5+δ, which detects ambient oxygen changes through significant variations in the Seebeck coefficient at room temperature, exploiting oxygen mobility in the material.

Contribution

The paper introduces a novel thermoelectric oxygen sensor based on GdBaCo2O5+δ that operates at room temperature, utilizing oxygen mobility and the insulator-metal transition for sensing.

Findings

Large Seebeck coefficient change (~10-13 μV/K) with oxygen partial pressure shifts.

Sensor response is rapid (~20 sec) and reproducible near the insulator-metal transition.

Sensor operates effectively at room temperature, suitable for cryogenic conditions.

Abstract

In this paper, we demonstrate a proof-of-concept oxygen sensor based on the thermoelectric principle using polycrystalline $GdBaCo_2O_{5+\delta}$ where 0.45<${\delta}$<0.55 (GDCO). The lattice oxygen in layered double perovskite oxides is highly susceptible to the ambient oxygen partial pressure. The as-synthesized GDCO sample processed in ambient conditions shows pure orthorhombic ($P_{mmm}$ space group) phase and a ${\delta}$-value close to 0.5 as confirmed from X-ray diffraction reitveld refinement. The X-ray photoelectron spectroscopy shows significant $Co^{3+}$ oxidation state in non-octahedral sites in addition to $Co^{3+}$ and $Co^{4+}$ in octahedral sites. The insulator-to-metal transition (MIT) is observed at nearly 340 K as seen in electrical resistivity and seebeck coefficient measurements. The seebeck coefficient shows a large change of about 10-13 $\mu$V/K with time constant of ~20 sec, at room temperature (300 K) when the gas ambience changes from 100% oxygen to 100% nitrogen and vice versa, under a constant temperature gradient of 1 K. The response in seebeck is found to be particularly large below MIT. The diffusion of oxygen into the lattice leading to hole doping shows a large change in carrier concentration resulting in a large change in the seebeck coefficient in insulating state. On the other hand, due to insignificant increase in already large carrier concentration in metallic state the change in seebeck is minimal. Nevertheless, below MIT the response is fairly reproducible within stoichiometry ${\delta}$ = 0.5 $\pm$ 0.05. This principle shall be of significant utility to design the oxygen sensors which work at room temperature or even cryogenic temperatures.