Effects of tungsten substitution on the transport properties and mechanism of fast oxide-ion conduction in La2Mo2O9

Sinterability, reducibility, and electrical conductivity of fast oxide-ion conductors La1.8R0.2MoWO9 (R=Pr, Nd, Gd and Y)

“…In the last decade, researchers have examined various types of cationic substitutions on La or Mo sites to improve the performance of LAMOX electrolytes [6][7][8][9][10][11][12][13][14]. Several types of substitutions can stabilize the highly conductive β-phase at room temperature, but only substitution of W on the Mo site can effectively improve the phase stability of the electrolyte at low oxygen partial pressures [15][16][17][18][19][20][21][22]. While the solubility of tungsten in La 2 Mo 2 O 9 is 80% [16], recent research suggests that the substitution rate should be restricted to levels lower than 60% because the β form with high W contents is not stable in air above 973 K [22].…”

“…The stability of La 2 Mo 2 O 9 in reducing atmospheres increases but its conductivity decreases with increasing W concentration [18]. Georges et al [17] suggested that the optimum content of substituted W is 50 mol%. Thus, this value was adopted in this study.…”

Surface enhancement of oxygen exchange and diffusion in the ionic conductor La2Mo2O9

“…Many studies have now effectively proved that substituting the La site with Gd [4], Er, Dy, [5] and others [6] can suppress the phase transition and stabilize the conducting β phase. Moreover, substitution of the Mo site with W can also improved the material by increasing its resistance to the reducibility of Mo [7]. These substituted derivatives are referred to as the LAMOX family (the substituted La 2 Mo 2 O 9 materials).…”

Ion dynamics study of La2Mo2O9

“…Attempts were made by different workers to stabilize the high-temperature form at room temperature by substitutions at La +3 and Mo +6 sites [5][6][7]. Whether these substitutions increase the conductivity or not is controversial [5,[8][9][10].…”