Phase transitions in the H+-conducting perovskite ceramics by the quasi-elastic neutron and high-pressure Raman scattering

Abstract

H + -containing lanthanide-doped perovskites A (Ba, Sr etc.)B(Zr, Ce, Ti etc.)O 3 are potential ceramic membranes for fuel cell and medium temperature water electrolysis (300-800°C). The comparison studies of the hydrated and non-hydrated Yb-doped BaZrO 3 and SrZrO 3 were performed by thermal expansion, medium-high temperature neutron and room-temperature high-pressure Raman scattering. Neutron diffraction and elastic/quasielastic studies carried out for BaZrO 3 ceramic show the presence of the protons, their successive diffusion above ∼600°C, and then their departure above 750°C (under vacuum). Phase transitions and their modification by proton insertion are discussed. A high-pressure Raman study of SrZrO 3 performed at room temperature in the diamond anvil cell reveals the presence of two pressure-induced phase transitions at about 5 and 22 GPa and confirms that proton insertion modifies the phase transition sequences.

Raman Intensity: An Important Tool in the Study οf Nanomaterials and Nanostructures

“…Additionally, this paper completes the review recently published considering the relationship between the Raman signature, grain size and mechanical properties of nanosized or nanostructured materials [2]. The Raman intensity analysis allows us characterizing the complex physical behaviour for better possible industrial application in the case of perovskites: high temperature protonic conductors [4] and ferroelectric relax- * corresponding author; e-mail: philippe.colomban@glvt-cnrs.fr ors PbMg 1/3 Nb 2/3 O 3−x PbTiO 3 (PMN-PT) solid solutions [5]. This analysis is also essential to determine the composition, technology and age of the Cultural Heritage objects made of glass, glaze and enamel or to understand and optimize optical devices made of glass containing dispersed metal nanoparticles [6][7][8][9][10][11][12].…”

“…• C in this compound [4]. This phase transition can be better manifested by the relative intensity ratio of the stretching mode located near 740 cm −1 vs. the bending one near 465 cm −1 (see Fig.…”

“…The other ions (A-ions) are highly ionic and contribute to the translation oscillation modes which couple themselves with other vibrational modes of the neighbouring entities: translations and rotations/libration of iono-covalent BO 6 leading to the wave number shifts. Low wave number region (100-250 cm −1 ) chiefly involves cationic network and the lattice modes, while a 250-800 cm −1 spectral range reveals the bending and stretching modes of the covalent bonded octahedron [3,4].…”

“…)B 4+ (Zr, Ce, Ti etc. )O 3 belong to the family of high temperature protonic conductors and might be used as membranes of the solid oxide fuel cell and water electrolyser [4,13,14]. The presence of protons is not intrinsic to their structure.…”

“…These Raman spectra consist of number of broad, not intense bands [4]. The presence of the Raman spectrum for these materials is contradictory with a description of the X-ray diffraction pattern with the cubic symmetry and the P m3m space group ( [4] and references therein), because for such cubic symmetry the first-order Raman activity is forbidden [15,16]. This suggests that the symmetry, at least at the local Raman scale within the analyzed spot (≈ few µm 2 ), is lower than the cubic mean one.…”