High‐Temperature Proton Conduction in LaSbO₄

Abstract

Lanthanum orthoantimonate was synthesized using as olid-state synthesis method.T oe nhancet he possible protonic conductivity,s amples with the addition of 1mol %C ai nL a-site were also prepared. The structure was studied by the meanso fX-ray diffraction, which showedt hat both specimens weres ingle phase. The materials crystallized in the space group P2 1 /n. Dilatometry revealedt hat the materiale xpanded non-linearly with the temperature. The nature of this deviation is unknown; however,t he calculated linearf raction thermal expansion coefficient was 9.56 10 À6 K À1 .E lectrical properties studies showedt hat the material is ap rotonc onductor in oxidizing conditions, which was confirmed both by temperature studiesi nw et in dry air,b ut also by the H/D isotopee xchangee xperiment. The conductivity was rather modest, peakinga tt he order of 10 À6 Scm À1 at 800 8C, but this could be further improved by microstructure and doping optimization.T his is the first time protonic conductivity in lanthanum orthoantimonates is reported. Proton conducting ceramics (PCCs) are materials exhibiting ionic conductivityi nw hichp roton (H +)i sacharge carrier. [1] This class of materials has gathered interest over the years for their potential applications.E specially the so-called triple conductingo xides, that is, materials with three mobile charge carriers (protons, oxygen ions, and electron/electron holes) were discovered and studied as potential electrode materials. [2-5] The increased interest led to developing highly-efficient fuel cells [5-7] and steam electrolyzers. [8] This interest stems from the fact that PCC-based devices can operate with high efficiencies while being cost-competitive in comparison to traditional solid oxide fuel cells. [5, 9] Apart from that, new typeso fe lectrochemical devices have been developed. Such devicesc an be used for the synthesis of ammonia, [10, 11] conversion of methane into aromaticsi namembraner eactor, [12] or thermo-electrochemical production of hydrogen from methane. [13]

Proton and Oxide Ion Conductivity in Palmierite Oxides

“…Sr3V2O8 in humidified air compared with the proton conductivities of La0.8Ba1.2GaO3.9 (LBG) 27 , La0.99Ca0.01NbO4 (LNO) 22 , La0.99Ca0.01TaO4 (LTO) 23 , La0.99Ca0.01VO4 (LVO) 24 , La0.99Sr0.01AsO4 (LAO) 25 , La0.99Ca0.01SbO4 (LSO) 26 , Ba3YGa2O7.5 (BYG) 53 , La3Ga5.06Si0.94O14 (LGS) 54 , La4GaTiO9.5 (LGO) 55 .…”

“…18,19,20 Reports of significant proton or oxide ion transport in oxide structures constituted by isolated tetrahedral units are on the other hand relatively scarce. Examples comprise proton conduction in acceptor-doped scheelite-and monazite-type oxides LaMO4 (M = P, V, As, Nb, Sb, Ta) 21,22,23,24,25,26 , lanthanum-barium gallates of general formula La1-xBa1+xGaO4-x/2, 27,28 and acceptor-doped Gd3GaO6. 29 Similarly, oxide ion conduction has been reported only in a few structural families constituted by isolated tetrahedral units, namely apatites and scheelites.…”

Solid oxide proton conductors beyond perovskites

“…Anode supported fuel cell with La0.99Ca0.01NbO4-δ electrolytes have shown modest peak power densities (24 mW cm −2 at 750 °C) due to the large polarization resistance between the electrodes and the electrolyte (20 -40 Ω cm 2 at 800 °C) 155,157,158 . Acceptor doped monazite-type systems LaVO4, LaAsO4, and LaSbO4 also present significant proton conductivity under humidified atmosphere 159,160,161 . The monoclinic monazite structure is similar to the scheelite structure and is composed by isolated distorted MO4 tetrahedra sharing their edges with LaO9 polyhedra 162 .…”

Praseodymium Orthoniobate and Praseodymium Substituted Lanthanum Orthoniobate: Electrical and Structural Properties

“…In the lanthanum sublattice, either acceptor dopants, i.e., Ca [ 17 ], Mg [ 18 ], Sr [ 19 ], Ba [ 20 ], or isovalent dopants, i.e., Ce (III) [ 21 ], Pr (III) [ 6 , 22 ], Nd and Sm [ 23 ], Tb (III) [ 7 ] and Yb [ 24 ], have been applied. In order to stabilize the structure and improve the conductivity, the substitutions in the niobium sublattice such as Al, Si, P, Ga, Ge and Bi [ 25 ], Ti [ 26 ], V [ 27 ], Cr, Mn, Sb [ 28 , 29 ] and Ta [ 27 ], Co [ 30 ], As [ 31 , 32 ], Zr [ 33 ], Mo [ 34 ], Sn [ 35 ] and W [ 36 ] have been tested.…”