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Effect of A‐ or B‐site doping of perovskite calcium manganite on structure, resistivity, and thermoelectric properties
Author(s) -
Mishra Avinna,
Bhattacharjee Sarama
Publication year - 2017
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.15015
Subject(s) - dopant , seebeck coefficient , electrical resistivity and conductivity , materials science , doping , analytical chemistry (journal) , manganite , perovskite (structure) , mineralogy , inorganic chemistry , condensed matter physics , chemistry , crystallography , thermal conductivity , physics , optoelectronics , chromatography , ferromagnetism , electrical engineering , composite material , engineering
Bismuth‐, lanthanum‐, and molybdenum‐doped calcium manganite (CaMnO 3 , abbreviated Mn113) are synthesized by solid‐state synthesis route from their respective oxide precursors at a same doping level ( x =0.05). Depending on the ionic sizes, trivalent dopants (Bi 3+ and La 3+ ) replace Ca 2+ (A site), while penta/hexavalent dopant Mo 5+ /Mo 6+ replaces Mn 4+ (B site) in the Mn113 structure. XRD of all three doped samples confirm formation of single phase. In all three samples, doping causes unit cell volume to expand, while volume expansion is maximum for the Mo‐Mn113. The transport behavior of the doped samples follows small polaron hopping mechanism. Resistivity of the doped samples depends not only on the carrier concentration but also on the effective bandwidth determined by the structural distortion introduced by the dopant ions. Bi‐Mn113 has highest resistivity at the both temperature end, while La‐Mn113 has the lowest. Thermopower is determined by the carrier concentration only and does not depend on dopant type, having value ~260 μV/K at 1000 K. At high (>800 K), S reaches a saturation value and becomes independent of T . La‐Mn113 is having highest figure of merit (zT) 0.19 at 1000 K.