Development of New Oxygen Ion Conductors Based on Nd4GeO8 and Nd3GaO6

• Published in: Chemistry of materials Vol. 17; no. 17; pp. 4479 - 4485
• Main Authors: Purohit, Ram Dayal, Chesnaud, Anthony, Lachgar, Abdessadek, Joubert, Olivier, Caldes, Maria Teresa, Piffard, Yves, Brohan, Luc
• Format: Journal Article
• Language: English
• Published: American Chemical Society 23.08.2005
• Subjects: Chemical Sciences; Material chemistry
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/cm050537h

New oxygen ion conductors have been prepared by substituting Ga3+ for Ge4+ in Nd4GeO8, Zn2+ and Mg2+ for Ga3+ in Nd3GaO6, and Ca2+ and Sr2+ for Nd3+ in Nd3GaO6. A combustion technique using ethylenediamine tetraacetic acid has been developed to synthesize these materials at ∼900 °C, leading to powders with spherical particles of about 100−200 nm. The green pellets obtained through the combustion-synthesized powders could be sintered to ∼98% at 1250 °C. It was found that Nd4Ge1 - x Ga x O8 - x /2 are formed up to x = 0.10, Nd3Ga1 - x M x O6 - x/2 (M = Zn, Mg) up to x = 0.03, and Nd3(1 - x)M‘3 x GaO6 - 3 x /2 up to x = 0.03 and 0.015 for M‘ = Ca and Sr, respectively. These relatively small substitution rates induce a significant increase in oxygen ion conductivity (σ800 ° C = 0.2 × 10-2 S cm-1 for Nd4Ge0.9Ga0.1O7.95; σ800 ° C = 0.5 × 10-2 and 0.4 × 10-2 S cm-1 for Nd3Ga0.97M0.03O5.985 with M = Zn and Mg, respectively, and σ800 ° C = 0.6 × 10-2 and 0.7 × 10-2 S cm-1 for Nd2.91Ca0.09GaO5.955 and Nd2.955Sr0.045GaO5.9775, respectively) with respect to pure Nd4GeO8 (σ800 ° C = 2.8 × 10-4 S cm-1) and pure Nd3GaO6 (σ800 ° C = 2.7 × 10-4 S cm-1).