513 Research Article Received: 21 July 2008 Accepted: 27 September 2008 Published online in Wiley Interscience: 10 November 2008 (www.interscience.wiley.com) DOI 10.1002/jrs.2157 Indirect Raman identification of the proton insertion in the high-temperature [Ba/Sr][Zr/Ti]O 3 -modified perovskite protonic conductors † Aneta Slodczyk, a Philippe Colomban, a∗ Stephanie Willemin, b Olivier Lacroix b and Beatrice Sala b OH − and H 3 O + species in hydrates and simple oxides are rather well characterised from their IR, Raman and inelastic neutron points of view. For the H + (H 2 O) species in solid state the variability is well established and assignment remains discussed. The question of the vibrational signature of isolated proton (e.g. the ionic proton, a proton sharing its interaction with more than two acceptors) and its dynamic nature (proton gas, polaron,...) is open. H + -containing modified perovskites A(Ba,Sr,...) B(Zr,Ce,Ti,...)O 3 are potential ceramic membranes for fuel cell and medium temperature water electrolysis (300–800 ◦ C). Comparison studies of the protonated and non-protonated lanthanide/rare earth-modified perovskites of type Ba(Sr)Zr(Ti)O 3 as well as Al-modified BaTiO 3 show that a broad component centred at 2500 cm −1 is observed after ‘proton insertion’. Its intensity is correlated to the protonic species content as well as to the conductivity of the materials. The mixed nature of this feature is discussed: fluorescence related to the dangling bonds, A, B, C bands or new phenomena related to the ionic protons and associated electronic defect. Copyright c  2008 John Wiley & Sons, Ltd. Supporting information may be found in the online version of this article. Keywords: proton conductor; perovskite; Raman scattering; X-ray diffraction Introduction The perovskite-type oxide ceramics with a general formula A II B IV O 3 are one kind of the high-temperature protonic conductors [1–3] . Since the presence of protons is generally not intrinsic to their structure, they first must be modified with a few mol% trivalent cations at B-site to form the oxygen ion vacancies [1–6] which are after ‘filled’ by the protonic moieties during the annealing process in the presence of water vapour under high pressure at medium- to-high temperature. The inserted protons exhibit relatively high mobility and give rise to significant proton conduction [1–3] . Because of the high potential applications as membranes of the solid oxide fuel cell and water electrolysers, different perovskites A(Ba,Ca,Sr,Zn,La) B(Zr,Ce,Ta,In,Lu,Ti,Sc,Pr,Tb,Th,...)O 3 doped or modified by various elements (Y, Yb, Al ... ) are widely investigated [7 – 27] . To date, the so-called ‘water’ insertion is actually detected only by (1) thermogravimetric analysis (TGA) (a small weight loss, less than 0.5–1% between room temperature (RT) and 800 ◦ C [1] ), (2) changes of the unit-cell parameter, (3) (quasi- elastic) neutron scattering [9 – 13] and (4) conductivity. Differences have been reported between the infrared (IR) spectra (Ref. 4 and references therein), but assignments remain questioned for the broad features observed in the 2000–4000 cm −1 range. It should be stressed that the proton diffusion mechanism has not been definitively determined yet and even the nature of protonic species in these materials is still source of debate. Some authors claim the presence of hydroxyl groups (OH − ) [28,29] and explain the conductivity by combined M–O motion and the proton jump. Their vibrational assignments were rejected by other authors [7] . On the other hand, it was proposed that conducting protons share their coupling with the neighbouring oxygen environment to give an ionic proton [4] , as observed in some other proton-conducting structures [3,4] which can be mobile independently of the oxygen atoms. Because of the lack of covalent bonding, such an ionic proton does not have any well-defined Raman or IR signal and a specific signature is only observable to date by inelastic neutron scattering, which should be performed at low temperatures (<100 K) [30,31] . Therefore, alternative, indirect methods or imperfect conditions are interesting for the understanding of the nature of proton in the hydrogen-containing perovskites. In our opinion, one of a method is the Raman scattering. This technique can probe not only the protonic species (with a lower sensitivity than IR absorption) but also, especially, the perturbation of the host framework. To date, the proton insertion and its distribution within the perovskite ceramics have not been studied and fast non-destructive methods ∗ Correspondence to: Philippe Colomban, LADIR UMR 7075, CNRS & Universit´ e Pierre et Marie Curie – Paris 06, 2 rue H. Dunant, 94320 Thiais, Paris, France. E-mail: philippe.colomban@glvt-cnrs.fr † Dedicated to A. Novak (1928 – 2007). a LADIR UMR 7075, CNRS & Universit´ e Pierre et Marie Curie – Paris 06, 2 rue H. Dunant, 94320 Thiais, Paris, France b AREVA-NP/IEM, Place Eug` ene Bataillon, 34095 Montpellier, France J. Raman Spectrosc. 2009, 40, 513–521 Copyright c  2008 John Wiley & Sons, Ltd.