Improvement of bromide ion conduction in a lanthanum oxybromide-based solid by adjusting the electronegativity of the cation dopant

Evidence for enormous iodide anion migration in lanthanum oxyiodide–based solid

“…Figure 1C shows the temperature dependence of the conductivity of La 0.70 Sr 0.25 Zn 0.05 OI 0.70 and LaOI. For comparison, the conductivities of the LaOBr-based materials ( 22 ) were also plotted. The conductivity considerably improved by introducing Sr 2+ and Zn 2+ , and the value of 4.4 × 10 −6 S cm −1 at 400°C was approximately 70 times higher than that of LaOI.…”

“…In the halide series, the bromide anion (Br − ) has the largest ionic size [0.182 nm, (CN = 6) ( 1 )] among all the ion species whose conduction was quantified ( 21 , 22 ). Br − is also larger than the cesium cation [Cs + , 0.181 nm (CN = 6) ( 1 )], which is the largest cation among all nonradioactive elements.…”

“…( B ) XRD patterns of La 0.70 Sr 0.25 Zn 0.05 OI 0.70 and LaOI solids. ( C ) Temperature dependence of the conductivity for the La 0.70 Sr 0.25 Zn 0.05 OI 0.70 and LaOI solids along with the data of LaOBr-based materials ( 22 ). a.u., arbitrary units.…”

Mechanisms of point defect formation and ionic conduction in divalent cation-doped lanthanum oxybromide: first-principles and experimental study

“…16,19 Synthesizing mixed-anion compounds is one approach to overcome these disadvantages, [20][21][22][23][24][25] and lanthanum oxyhalide, LaOX (X: Cl, Br, and I), is one such halide-based mixedanion. [26][27][28][29][30] LaOX-based compounds are reported to exhibit halide ion conductivities of about 7.2 × 10 −3 , 1.0 × 10 −3 , and 4.4 × 10 −6 S cm −1 at 400 °C for oxychrolide, 26 oxybromide, 29 and oxyiodide, 30 respectively, despite the larger ionic radii of halide ions. In addition, these compounds are insoluble in water and thermodynamically more stable than simple halides.…”

“…Pure LaOBr has low ionic conductivity, and several divalent cations such as Mg, Ca, Zn, and Sr were added to improve its conductivity. 18,28,29,33 From the experimental approach, the Br − ion conduction was demonstrated by the dc electrolysis of La 0.90 Sr 0.10 OBr 0.90 , and the polarization behavior denied the O 2− ion migration. 33 The conduction mechanism in doped LaOBr is expected to be related to the halide ion vacancies similar to the LaOCl system, although this is not verified theoretically.…”