Effect of Na-doping on thermoelectric and magnetic performances of textured Bi2Sr2Co2Oy ceramics

Bi2Sr2-xNaxCo2Ox (x = 0.0, 0.025, 0.050, 0.075, 0.100, and 0.125) samples were prepared through the solid-state route and textured using the laser floating zone technique. Microstructural analysis of as-grown samples showed well oriented grains and a relatively high amount of secondary phases due to their incongruent melting. Annealing procedure has drastically decreased the number and amount of secondary phases. Moreover, Na-doping has further decreased the secondary phases content and improved grain alignment. These modifications have been reflected in a large decrease of electrical resistivity with the annealing procedure. The maximum power factor values have been obtained in 0.075 Na-doped annealed samples, 0.20 mW/K2m, which are much higher than the best values obtained in textured materials through hot uniaxial pressing. Magnetic properties were very similar for all samples, with paramagnetic Curie temperature and effective magnetic moment values of −48.6 K and ≈2 μB, respectively.This work is supported by Research Fund of Çukurova University, Adana, Turkey, under grant contracts no: FDK-2016-6105. The authors wish to thank the MINECO-FEDER (Project MAT2013-46505-C3-1-R), Universidad de Zaragoza (Project UZ2017-TEC-03), and the Gobierno de Aragón-FEDER (Research Groups T12 and T87) for financial support.Peer reviewe

Effect of Na-doping on thermoelectric and magnetic performances of textured Bi2Sr2Co2Oy ceramics

Bi2Sr2-xNaxCo2Ox (x = 0.0, 0.025, 0.050, 0.075, 0.100, and 0.125) samples were prepared through the solid-state route and textured using the laser floating zone technique. Microstructural analysis of as-grown samples showed well oriented grains and a relatively high amount of secondary phases due to their incongruent melting. Annealing procedure has drastically decreased the number and amount of secondary phases. Moreover, Na-doping has further decreased the secondary phases content and improved grain alignment. These modifications have been reflected in a large decrease of electrical resistivity with the annealing procedure. The maximum power factor values have been obtained in 0.075 Na-doped annealed samples, 0.20 mW/K2m, which are much higher than the best values obtained in textured materials through hot uniaxial pressing. Magnetic properties were very similar for all samples, with paramagnetic Curie temperature and effective magnetic moment values of -48.6 K and ?2 µB, respectively. © 2017 Elsevier LtdMAT2013-46505-C3-1-R Universidad de Zaragoza: UZ2017-TEC-03 FDK-2016-6105This work is supported by Research Fund of Çukurova University, Adana, Turkey , under grant contracts no: FDK-2016-6105 . The authors wish to thank the MINECO-FEDER (Project MAT2013-46505-C3-1-R ), Universidad de Zaragoza (Project UZ2017-TEC-03 ), and the Gobierno de Aragón-FEDER (Research Groups T12 and T87) for financial support. Authors acknowledge the use of Servicio General de Apoyo a la Investigación-SAI, Universidad de Zaragoza