Spectroscopic and transport properties of Ba‐ and Ti‐doped BaLaInO₄

Abstract

In this work, the local structure of the acceptor Ba1+хLa1–хInO4–0.5х and donor BaLaIn1–хTiхO4+0.5х doped solid solutions based on BaLaInO4 was investigated. The appearance of new types of the defects (oxygen vacancy and oxygen interstitial) in the crystal lattice was confirmed by the spectroscopic investigations. It was shown that for both solid solutions the same tendency of the increase in the symmetry of the structure and the expansion of interlayer space with increasing dopant concentration is observed. The changes in the transport properties (ionic conductivity) have the same tendency for both solid solutions. The increase in the oxygen‐ionic and protonic conductivity in the area of “low” dopant concentrations (x < 0.05) is due to the increase in the mobility of ions caused by the influence of geometric factor. The decrease in the ionic conductivity values in the area of “high” dopant concentrations (x > 0.05) is caused by the appearance of interaction between defects (concentration factor). The most conductive ionic (oxygen‐ionic and protonic) material with Ruddlesden–Popper (RP) structure based on BaLaInO4 is Ba1.1La0.9InO3.95 composition.

Materials AIILnInO4 with Ruddlesden-Popper Structure for Electrochemical Applications: Relationship between Ion (Oxygen-Ion, Proton) Conductivity, Water Uptake, and Structural Changes

“…The investigation of local structure of acceptor- and donor-doped samples based on BaLaInO 4 using Raman spectroscopy showed the presence of local disordering of the crystal lattice [ 88 , 89 ]. The acceptor doping led to the decrease in the coordination number of metal (barium and lanthanum) because of the formation of oxygen vacancies during doping (Equation (1)).…”

“…At the same time, the introduction of ions with bigger ionic radii Sr 2+ , Ba 2+ ( = 1.31 Å, = 1.47 Å, = 1.216 Å [ 87 ]) in the La 3+ -sublattice provides the increase of Ba,La−O1 bond length. The average bond length Ba,La−O increases what caused the expansion of unit cell in the ab direction and the decrease of octahedra [InO 6 ] titling [ 88 , 89 ]. This allows to say that acceptor doping of BaLaInO 4 led to the formation of less distorted structure.…”

“…The donor doping led to the appearance of “additional” (interstitial) oxygen O3 (Equations (2) and (3)). Consequently, the coordination number of some Ba 2+ - and La 3+ -cations increased, and the bond lengths Ba,La−O1 and Ba,La−O2 and lattice parameter a increased also [ 88 , 89 ]. The increase of the charge of dopant (Ti 4+ , Nb 5+ ) and the concentration of dopant led to a decrease of distortion of the structure.…”

Simultaneous Hetero- and Isovalent Doping as the Strategy for Improving Transport Properties of Proton Conductors Based on BaLaInO4

“…Over the past forty years, the proton-conducting solid oxides went beyond perovskites family ( Figure 1 ). After variously doped barium cerates and zirconates [ 8 , 9 , 10 ], classes of proton-conducting materials like hexagonal [ 11 , 12 , 13 , 14 , 15 , 16 , 17 ], oxygen-deficient [ 18 , 19 , 20 ], block-layered [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ] perovskites, brownmillerites [ 32 , 33 , 34 ], pyrochlores [ 35 , 36 , 37 , 38 ], apatites [ 39 ], monazites [ 40 , 41 , 42 ], gallium-based oxides [ 43 , 44 , 45 ], materials with fluorite- [ 46 , 47 , 48 ], fergusonite- [ 49 , 50 , 51 ], and weberite-types [ 52 , 53 ] of structures were described.…”

“…From the point of view of protonic conductivity, the layered perovskites based on BaLaInO 4 , SrLaInO 4 , BaNdInO 4, and BaNdScO 4 were investigated [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ]. The possibility of acceptor (Ca 2+ /Sr 2+ /Ba 2+ → La 3+ /Nd 3+ ) and donor (Zr 4+ /Ti 4+ /Nb 5+ → In 3+ ) doping was proven.…”