Defect Structure of Y1-yCayMnO3 and La1-yCayMnO3: I. Electrical Properties

✍ Scribed by J.W. Stevenson; M.M. Nasrallah; H.U. Anderson; D.M. Sparlin

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 339 KB
• Volume: 102
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1993.1020

✦ Synopsis

Electrical conductivity and the Seebeck coefficient of compositions in the system (\mathrm{Y}{1-y} \mathrm{Ca}{y} \mathrm{MnO}{3}) and (\mathrm{La}{1-y} \mathrm{Ca}{y} \mathrm{MnO}{3}) were studied to determine the mechanism of electrical transport and defect structure. Electrical conduction appeared to occur via a small polaron hopping mechanism for compositions with (0.30 \leq y \leq 0.80). The Seebeck coefficient data did not support the assumption that (\mathrm{Mn}) is present in (\mathrm{Ca}) doped Mn perovskites only in the +3 and +4 valence states. A new defect model was developed which includes the thermally excited disproportionation of (\mathrm{Mn}^{3+}) into (\mathrm{Mn}^{2+}) and (\mathrm{Mn}^{4+}) pairs. The Seebeck data were explained with this model by assuming that divalent (\mathrm{Mn}) cations were site blockers in the conduction process. 1993 Acaderic Press, inc.