Potentiometric CO2 Gas Sensor Prepared from Lithium Ionic Conductors.

Ionic and Electronic Conductivities and Fuel Cell Performance of Oxygen Excess-Type Lanthanum Silicates

“…1, was originally discovered by Nakayama et al 1,2 in 1995. This material is notable because of its low activation energy for conduction, while the reported ionic conductivity was about 10 −3 S cm −1 at 973 K. Later, the total electrical conductivity ͑͒ was found to be enhanced through a densification, 3 a slight replacement, [4][5][6] and increase in x, i.e., the ratio of La to Si. 7 The optimized composition La 10 ͑Si 5.7 Mg 0.3 ͒O 27−␣ with of 2 ϫ 10 −2 S cm −1 at 973 K was developed by Yoshioka.…”

“…7 The optimized composition La 10 ͑Si 5.7 Mg 0.3 ͒O 27−␣ with of 2 ϫ 10 −2 S cm −1 at 973 K was developed by Yoshioka. 6 Their leading work [1][2][3][4][5][6][7] on this new material should be noted. Without a doubt, they have thrown light on this unknown material as a candidate for the new electrolyte in intermediate temperature fuel cell application.…”

Oxygen Ionic and Electronic Transport in Apatite-Type Solid Electrolytes

“…Significant oxygen ionic conductivity was recently reported for apatite-type silicates A 10Ϫx (SiO 4 ) 6 O 2Ϯ␦ , where A corresponds to rare-earth and alkaline-earth metal cations. [5][6][7][8][9][10][11][12][13] These solid electrolytes may be of great practical interest when we consider the low cost of raw materials and well-developed technologies for SiO 2 -based film processing in the electronic industry. The apatite lattice can be viewed as a ''hybrid'' structure consisting of covalent SiO 4 tetrahedra and ionic-like La/O channels.…”

“…As for perovskite-and K 2 NiF 4 -type ionic conductors, 14 the oxygen transport in Ln 10 Si 6 O 27 (Ln ϭ La,Pr,Nd,Sm,Gd,Dy) increases with increasing radius of Ln 3ϩ cations; maximum conductivity is observed for the Lacontaining phase. 6,11 Due to poor sintering and different processing techniques, the conductivity values reported in the literature vary greatly, for example, from 8.4 ϫ 10 Ϫ5 to 4.3 ϫ 10 Ϫ3 S/cm at 773 K for La 10 Si 6 O 27 . 5,6,10 The ionic transport in La 9.33 Si 6 O 26 is lower than that in La 10 Si 6 O 27 , but higher compared to La 8 Sr 2 Si 6 O 26 , where the vacancy diffusion mechanism dominates.…”

“…6,11 Due to poor sintering and different processing techniques, the conductivity values reported in the literature vary greatly, for example, from 8.4 ϫ 10 Ϫ5 to 4.3 ϫ 10 Ϫ3 S/cm at 773 K for La 10 Si 6 O 27 . 5,6,10 The ionic transport in La 9.33 Si 6 O 26 is lower than that in La 10 Si 6 O 27 , but higher compared to La 8 Sr 2 Si 6 O 26 , where the vacancy diffusion mechanism dominates. 10,13 This suggests a significant role of interstitial migration and a possible improvement in the conductivity when apatite phases contain more than 26 oxygen ions per unit formula.…”