Improvement of oxygen-ionic and protonic conductivity of BaLaInO4 through Ti doping

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

“…Transport properties of the solutions Ba 1+ х La 1– х InO 4–0.5 х and BaLaIn 1– х Ti х O 4+0.5 х were investigated earlier in our previous works. [ 41,43 ] As we can see from Figure 4, there is a valuable increase in the ionic conductivity values (up to ~1.5 order of magnitude) in the area of very small dopant concentrations ( x < 0.05). It is obvious that such low dopant concentrations cannot provide such large increase in the conductivity values.…”

“…The results of Rietveld refinement of obtained XRD data and the values of the lattice parameters of the samples were provided in our previous works. [ 41,43 ] The acceptor Ba 2+ → La 3+ and donor Ti 4+ → In 3+ doping of cationic sublattices of BaLaInO 4 leads to the formation of the solid solutions Ba 1+ х La 1– х InO 4–0.5 х and BaLaIn 1– х Ti х O 4+0.5 х in the composition ranges 0 ≤ x ≤ 0.15. The introduction of ions with lower oxidation state (Ba 2+ ) in the La 3+ ‐sublattice causes the appearance of oxygen vacancies in the structure: The doping of the In 3+ ‐sublattice by the ions with higher oxidation state (Ti 4+ ) leads to the formation of interstitial oxygen: Despite the different ratios of ionic radii of dopants ions and host ions in the structure ( = 1.216 Å, = 1.47 Å, = 0.80 Å, = 0.605 Å [ 48 ] ), the same tendency of increase in the lattice parameter a (Figure 1) and, correspondingly, in the size of interlayer space [ 36,43 ] is observed.…”

“…The results of Rietveld refinement of obtained XRD data and the values of the lattice parameters of the samples were provided in our previous works. [41,43] The acceptor Ba 2+ ! La 3+ and donor Ti 4+ !…”

“…Despite the different ratios of ionic radii of dopants ions and host ions in the structure (r La 3 + = 1.216 Å, r Ba 2 + = 1.47 Å, r In 3 + = 0.80 Å, r Ti 4 + = 0.605 Å [48] ), the same tendency of increase in the lattice parameter a (Figure 1) and, correspondingly, in the size of interlayer space [36,43] is observed. In the case of acceptor doping this increasing is due to the introduction of ions (Ba 2+ ) with bigger radius.…”

“…All of these three factors were taken into account by us during investigations of transport properties of compositions obtained based on BaLaInO 4 characterized by the RP structure. It was shown that doping (acceptor [ 40,41 ] and donor [ 42,43 ] ) leads to a significant increase in the oxygen‐ionic and protonic conductivity. In addition, it was proved that most investigated compositions based on BaLaInO 4 demonstrate nearly pure protonic type of conductivity under wet air and low (<400°C) temperatures.…”