Electrochemical properties of dense (La, Sr)MnO_3−δ films produced by pulsed laser deposition

The electrical conductivity and the electrochemical properties of dense La0.85Sr0.15MnO_3−δ (LSM) films, prepared using Pulsed Laser Deposition (PLD) have been investigated. The nano-structure of the LSM films has been characterized using scanning electron microscopy (SEM). The oxygen transport properties of the films were studied using electrochemical impedance spectroscopy (EIS) on symmetrical cells. Electrical conductivity measurement were carried out in an oxygen partial pressure range from 1 to 0.0032atm, and a temperature range from 950 to 700°C. The electrical conductivity at 800°C was 116 S cm⁻¹ and did not vary with the pO2. Impedance spectra were recorded in the temperature range from 600 to 950°C in the oxygen partial pressure range from 0.06 to 1.00atm. At 900°C and 1.00atm the area specific resistance was 30.6Ωcm2 and an activation energy of 2.7eV was found. The ASR increased with decreasing pO2. Based on the impedance spectra an oxide ion conductivity of 5.0×10⁻¹ S cm⁻¹ was found at 900°C and pO2=1.00atm. The characteristic length, at which the oxide transport reaction switch from being limited by bulk diffusion to that of surface exchange, was estimated to be approximately 220 and 130nm at 700 and 900°C, respectively.