['While', 'impedance', 'spectroscopy', 'is', 'a', 'quite', 'common', 'method', 'to', 'investigate', 'mixed', 'conducting', 'thin', 'film', 'electrodes', ',', '[', '6,10–12', ']', 'oxygen', 'tracer', 'experiments', 'are', 'often', 'performed', 'on', 'bulk', 'samples', '[', '13–16', ']', '.']