Abstract

As one of the most promising candidates to provide metallic interconnector the ability against oxidization at elevated temperature, conductible spinel has drawn a lot of attention in recent years. However, it is suffering poor stability during the preparation process, such as plasma spray. This work is proposed to concentrate on the preparation of highly conductible spinel coating. MnCo₂O₄ spinel coatings are successfully obtained by atmospheric plasma spray. Conductivity test is carried out at 700 °C with duration up to 15 hours. Stability and variation in microstructure are characterized by SEM, XRD, TEM and differential scanning calorimetry (DSC). Resultantly, coatings are found intensively densified that cracks and gaps are expelled, and number of pores is reduced. The as-sprayed coatings are found of more CoO and less MnCo₂O₄, while the densified coatings are composed of more MnCo₂O₄ and less CoO. The measured conductivity of samples is 7.99S/cm, 4.00S/cm and 39.4S/cm for sample No.1, No.2 and No.3 respectively. Sample No.3 exhibit the best stability with the lowest specific heat flux of 0.8mW/mg and the biggest average grain size of 227nm while the specific heat flux of sample No.2 is as high as 1.8mW/mg and the average grain size is 83nm. Both the densification, phase composition and the grain size contribute to the conductivity of the coatings.

Keywords: MnCo₂O₄ spinel; Metallic interconnect; SOFC; Conductivity; Densification; Phase composition