Vibrational spectroscopy on protons and deuterons in proton conducting perovskites

A short review of IR-spectroscopy on protons in perovskite structure oxides is given. The nature of possible proton sites, libration and combination tones and degree of hydrogen bonding is emphasised. Three new spectroscopic experiments and/or interpretations are presented. An IR-microscopy experiment was performed on the protonic conductor Ba3(Ca1+xNb2−x)O9−δ, x=0.18. The H/D concentration profile of a cross-section of the sample after partial isotopic exchange can be visualised; proton containing La0.9Ca0.1ErO3 was studied up to 200 °C by Raman spectroscopy. At 200 °C, the OH-stretch cannot be observed due to thermal broadening, but the peak reappears upon cooling; the OH and OD absorption bands in BaCe1−xNdxO3 are very broad and, in addition, an electronic transition of Nd+3 is observed at 1900–1930 cm−1; finally, IR reflectance spectroscopy on BaZr0.9Y0.1O3, La0.8Sr0.2ScO3, La0.9Sr0.1Sc0.9Mg0.1O3 and SrCe0.95Y0.05O3 shows at least three types of proton positions.