Vibrational properties of proton conducting double perovskites

Raman and infrared spectroscopy results of protonated and dry samples of the proton conducting double perovskites Sr3CaZr0.5Ta1.5O8.75 and Ba3Ca1.18Nb1.82O8.73 (BCN18) are presented. As confirmed by the Raman spectra, the incorporation of protons leads to only small distortions in the host lattice of the perovskites. However, the intensity growth of a band at approximately 650 cm− 1 in the Raman spectrum of Sr3CaZr0.5Ta1.5O8.75 after protonation may be related to a symmetry reduction towards a monoclinic structure. The O–H stretch region in the infrared spectra of Sr3CaZr0.5Ta1.5O8.75 and BCN18 are quite different. Stronger bands in the 2000–2500 cm− 1 range in Sr3CaZr0.5Ta1.5O8.75 may be related to the higher concentration of oxygen vacancies in this material after protonation.