The competitive ionic conductivities in functional composite electrolytes based on the series of M-NLCO (M = Ce0.8Sm0.2O2-δ, Ce0.8Gd0.2O2-δ, Ce0.8Y0.2O2-δ; NLCO = 0.53Li2CO3–0.47Na2CO3)

In order to identify competitive ion-conducting materials in ceria-carbonates composite electrolytes, M-NLCO (M = Ce0.8Sm0.2O2-δ (SDC), Ce0.8Gd0.2O2-δ (GDC), Ce0.8Y0.2O2-δ (YDC); NLCO = 0.53Li2CO3–0.47Na2CO3) sintered at different temperatures (600° C, 625° C, 650° C, 675° C and 700° C) have been prepared and characterized. It is found that independent of systems, the 675° C-sintered composites in M-NLCO always present the highest conductivities because of the best NLCO distribution and interfacial microstructures. Moreover, among three composites (sintered at 675° C), the total ( σ t ) and grain boundary ( σ g b ) conductivities measured at 600° C are ranked as: SDC-NLCO ( σ t − SDC - NLCO 600 ° C = 9.1 × 10 − 2 Scm − 1 , σ g b − SDC - NLCO 600 ° C = 28.1 × 10 − 2 Scm − 1 ) ﹥ GDC-NLCO ( σ t − GDC - NLCO 600 ° C = 5.8 × 10 − 2 Scm − 1 , σ g b − GDC - NLCO 600 ° C = 18.9 × 10 − 2 Scm − 1 ) ﹥ YDC-NLCO ( σ t − YDC - NLCO 600 ° C = 3.1 × 10 − 2 Scm − 1 , σ g b − YDC - NLCO 600 ° C = 12.6 × 10 − 2 Scm − 1 ), which is attributed to ionic-radius compatibility between the dopant and the host as well as the NLCO distribution and interfacial microstructures. It can be concluded that ionic-radius compatibility between the dopant and the host, NLCO distribution and interfacial microstructures have important effects on improving ionic conductivities for ceria-carbonates composite electrolytes.