Determining thermal conductivity of plasma sprayed TBC by electrochemical impedance spectroscopy

Thermal conductivity, K, of free-standing air plasma sprayed (APS) thermal barrier coatings (TBCs) after exposure at temperatures of 1100, 1200, and 1350 °C for 3, 10, 17, 24, and 120 h was measured using laser flash (LF) technique and differential scanning calorimeter (DSC), and correlated with the spectra of electrochemical impedance spectroscopy (EIS). High-temperature exposure of TBCs increases the thermal conductivity as well as the electrochemical conductance, CtT, with an increase in exposure temperature and exposure time. A linear relationship between thermal conductivity, K, and electrochemical conductance, CtT, has been found. The result has demonstrated that electrochemical impedance technique holds the promise enabling to assess and monitor the thermal conductivity of free-standing TBCs.