Synthesis of transition metal doped lanthanum silicate oxyapatites by a facile co-precipitation method and their evaluation as solid oxide fuel cell electrolytes

Transition metal doped apatite La10Si6-xCoxO27-delta (x = 0.0; 0.2; 0.8) and La10Si5.2Co0.4Ni0.4O27-delta are synthesized by co-precipitation method followed by sintering. The precursor precipitates and apatite products are characterized by XRD, FTIR, TGA/DTA, Raman Spectroscopy, SEM-EDX and electrochemical impedance spectroscopy. The presence of apatite phase with hexagonal structure is confirmed through the XRD results. The conductivity measurements of the samples sintered at 1000 degrees C show that the ionic conductivity increases with increasing content of Co2+ doping into apatite that is further increased by co-doping of Ni2+. The Co doped apatite (La10Si5.2Co0.8O27-delta) exhibited conductivity of 1.46 x 10(-3) S cm(-1) while Co-Ni co-doped sample (La10Si5.2Co0.4Ni0.4O27-delta) exhibited highest conductivity of 1.48 x 10(-3) S cm(-1). The maximum power density achieved is also for Co, Ni co-doped sample i.e., 0.65 W cm(-2) at 600 degrees C. The results represented show that Co and Ni enhances the SOFC performance of apatite and makes it potential electrolyte candidate for solid oxide fuel cell application.

Automated summary

Transition metal doped apatite La10Si6-xCoxO27-delta and La10Si5.2Co0.4Ni0.4O27-delta were synthesized by co-precipitation method followed by sintering. The conductivity of the samples increased with the content of Co2+ doping and was further increased by co-doping of Ni2+. The co-doped sample (La10Si5.2Co0.4Ni0.4O27-delta) exhibited the highest conductivity and achieved the maximum power density, making it a potential electrolyte candidate for solid oxide fuel cell application.