Langasite-based Microbalance for Determination of the Non-stoichiometry in Praseodymium-Cerium Oxide Thin Films at Elevated Temperatures

摘要

The oxygen partial pressure dependent non-stoichiometry of praseodymium-cerium oxide thin films (Pr_(0.1)Ce_(0.9)O_(2-δ), PCO) is investigated at temperatures between 700 and 900°C. The non-stoichiometry of PCO is determined gravimetrically using a high-temperature microbalance consisting of piezoelectric langasite (La_3Ga_5SiO_(14)) resonators. Shifts of the resonance frequency are correlated with mass changes caused by oxygen incorporation/release using the Sauerbrey equation and converted into the oxygen non-stoichiometry of PCO. Chemical and mechanical properties of the PCO films might influence the resonance frequency. Single-side deposition of PCO onto the resonators results in calculated non-stoichiometry values which exceed literature data for bulk PCO. A potential explanation is mechanical bending of the resonators due to thermo-chemical expansion. Resonators coated on both sides with PCO show smaller frequency shifts corresponding to a non-stoichiometry of up to δ = 0.07, which are close to literature data.