Effects of synthesis method on stoichiometry, structure and electrical conductivity of CaMnO3−δ

Neutron powder diffraction studies in CaMn1‐xCuxO3 (x = 0, 0.2)

“…It suggests that the doped Cu ions in the Mn site is in the form of Cu 2+ ion, because its ionic size (0.73Å) is larger than the Mn 4+ ions (0.53Å). The Mn-O bond length is found to be in the range of 1.89 to 1.90Å and are comparable to those reported by Jorge et al [27] in CaMnO 3 and other Mn 4+ rich compounds [28]. These bond lengths suggest that the Mn ions in this material is predominantly in Mn 4+ state.…”

Synthetic Methods for Perovskite Materials; Structure and Morphology

“…On the other hand, the average grain size of the sample obtained by glycine-nitrate route is about 200 nm, almost an order of magnitude smaller. The higher calcination temperature and longer reaction time required to obtain the samples in the ceramic process can explain the bigger grain size showed for these samples (Melo Jorge et al, 2001). For the application as SOFC cathodes, samples with small and homogeneous particle sizes are usually preferred.…”

Granular and Lamellar Thermoelectric Oxides Consolidated by Spark Plasma Sintering

“…To increase the electrical conductivity, reduce the thermal conductivity, and thereby improve the figure-of-merit ZT, alternative TE oxides have been suggested as potential candidates for high-temperature TE applications. [5][6][7] The perovskite CaMnO 3 has been intensively studied [8][9][10][11][12][13][14][15] for its superconducting, magnetic, and electric properties, and the colossal magnetoresistance effect has been widely reported in this compound. 13,16,17 Dealing with TE properties, two approaches have been reported to modify the carrier concentration in order to enhance the material performance.…”

“…The first approach is Ca-site substitution by La or Sm, 11,15,16,18 and the second approach is doping of Mn-sites with cations such as Nd, Ta, Ru, and Rh. 9,13,17 Various routes based on solution chemistry methods such as the nitrate method, 18,19 citrate gel with self-combustion, 10 and coprecipitation 20 have been used to prepare homogeneous and fine perovskite oxide powders. Whatever the synthesis method applied, TE performance still strongly depends on the densification and structuration from the nano-to the macroscale of the resulting samples.…”