Substitution and proton doping effect on SrZrO₃ behaviour: high‐pressure Raman study

Abstract

The high-pressure Raman studies of pure, Yb-modified, protonated and non-protonated SrZrO 3 dense ceramics were performed between 0.1 and 40 GPa using a diamond anvil cell. Lanthanide-modified, protonated SrZrO 3 perovskites are potential materials for electrolytic membrane in fuel cells and electrolysers working at medium temperature. The comparison of the Raman spectra shows important differences in the pressure behaviour between the pure and Yb-modified SrZrO 3 ceramics. SrZrO 3 exhibits a rigid structure without any structural modification, whereas for both SrZr 0.93 Yb 0.07 O 2.965 and SrZr 0.93 Yb 0.07 O 2.962 H 0.003 a sequence of structural modifications at 10, 20 and 35 GPa is revealed. The character of these structural modifications is very similar to that observed as a function of the temperature (orthorhombic Pnma 750 • C → pseudo-tetragonal Imma 840 • C → tetragonal I4/mcm 1070 • C → cubic Pm3m), which suggests that they can be considered as the phase transitions. Despite the low level of proton content (0.3% mole/mole), significant difference between protonated and non-protonated compounds is observed for the 700-750 cm −1 doublet assigned to the Zr-O octahedron stretching mode, perturbed by an oxygen atom vacancy and/or neighbouring Yb ion. The location of proton is discussed.

Chemical and structural stability of La0.6Sr0.4Co0.2Fe0.8O3− ceramic vs. medium/high water vapor pressure

“…The as-prepared ceramic was treated under high/medium water vapor pressure (20/40 bar, 550 1C, CO 2 -free and CO 2 -saturated water) for period of 8-47 days using the home designed autoclave device [20,[28][29][30][31][32]. This device is equipped with a temperature and pressure controller, which allows us to follow the protonation process/incorporation of water/protonic species from the pressure drop.…”

“…The protonation process leads to subtle modifications of a material structure whatever the small amount of incorporated protons [28][29][30][31][32][33][34][35]. The quantity of CO 2 dissolved in the water used is one of the stringent parameters.…”

“…Careful analysis of the secondary phases with usual analytical techniques permits the study of the corrosion mechanism. Following the procedure of the previous studies, the LSCF6428 ceramic sample was treated under medium/high water vapor pressure ($ 20 and $ 40 bar) at 550 1C for several days using a home-designed autoclave device [20,[28][29][30][31][32]. Two kinds of water were used: i) CO 2 -free water and ii) CO 2 -saturated water.…”

High P–T Raman study of transitions in relaxor multiferroic Pb(Fe0.5Nb0.5)O3

“…It is important to note that due to the relaxor ferroelectric behavior of PFN and the formation of polar nanoregions because of B-site perovskite disorder, the local structure will differ from the average structure. In addition, as shown in previous studies, [17] important information can be extracted from the Raman intensity for perovskite-like materials. Raman scattering is therefore an invaluable tool for extracting information from these complex systems.…”

High water pressure - high temperature autoclave for in situ Raman study of fuel cell/electrolyser materials.

“…Different Ln/RE-modified, protonated (the proton content is not intrinsic to the pristine structure) perovskite ceramics, i.e. A(Sr,Ba,La)B(Zr, Ce, Ti, Sn, Ta, Nb,W)O 3-δ Hε, are widely investigated [3][4][5][6][7][8][9][10][11][12][13][14][15] prior to the application as an electrolytic membrane and/or electrode components of fuel cells, water electrolysers and CO 2 /syngas converters [1][2][3][4]. In order to be used in an industrial device, a ceramic membrane should exhibit significant mechanical and (electro)chemical stability to guaranty a long lifetime, ~ 10000 hours.…”