Electronic Percolation Threshold of Self-Standing Ag-LaCoO₃ Porous Electrodes for Practical Applications

• Main Authors: Stanica Enache, Mirela Dragan, Mihai Varlam, Konstantin Petrov
• Format: Article
• Language: English
• Published: MDPI AG 2019-07-01
• Series: Materials
• Subjects: perovskites; sintering; electrical resistivity; composite media; effective medium theory
• Online Access: https://www.mdpi.com/1996-1944/12/15/2359

Perovskite LaCoO<inline-formula> <math display="inline"> <semantics> <msub> <mrow></mrow> <mn>3</mn> </msub> </semantics> </math> </inline-formula> materials have various applications, from selective permeable membranes and gas sensing devices to water splitting applications. However, the intrinsic electrical resistivity of the perovskite limits the applicative potential. To overcome that, Ag powder was used with LaCoO<inline-formula> <math display="inline"> <semantics> <msub> <mrow></mrow> <mn>3</mn> </msub> </semantics> </math> </inline-formula> to obtain porous composite electrodes with enhanced conductivities. For that, a series of composite Ag-LaCoO<inline-formula> <math display="inline"> <semantics> <msub> <mrow></mrow> <mn>3</mn> </msub> </semantics> </math> </inline-formula> powders were prepared into pellets and pre-sintered at various temperatures up to 1000 <inline-formula> <math display="inline"> <semantics> <msup> <mrow></mrow> <mo>∘</mo> </msup> </semantics> </math> </inline-formula>C. Their structural properties and morphology were investigated by X-ray diffraction and scanning electron microscopy. The electronic transport of compacted specimens was studied by impedance spectroscopy. The results indicate that the presence of Ag acts as pre-sintering additive to obtain porous electrodes, with porosity values as high as 40% at 50 vol. % Ag. Moreover, the overall electrical resistivity of the composite electrodes varied well over four orders of magnitude. The results are discussed within the generalized Bruggeman theory for effective media comprising arbitrarily shaped metallic and semiconducting inclusions.