Thermoelectric properties of n-type Ca1−xDyxMn1−yNbyO3−δ compounds (x=0, 0.02, 0.1 and y=0, 0.02) prepared by spray-drying method

Effect of the sintering temperature on the properties of nanocrystalline Ca1−xSmxMnO3 (0≤x≤0.4) powders

“…The Ca 0.9 Sm 0.1 MnO 3 phase exhibits identical behaviour to the published recently by Wang et al [16] for the same phase prepared by traditional solid-state reaction method at 1623 K, although they have obtained a T MI value slightly lower (T MI = 365 K) than the one obtained in the present work. Below T MI the samples present semiconductor behaviour; this is in agreement with the studies reported by other authors [13][14][15]17,18,41] for the electron-doped Ca 1−x Sm x MnO 3 (x ≤ 0.4) samples for temperatures lower than 300 K. According to the literature [7,12,[41][42][43][44][45] the MI transition can be attributed to the charge-ordering phenomena (CO), i.e., the ordering of the Mn 3+ and Mn 4+ species over the manganese lattice. In this case, the onset of the CO is coincident with an increase on the electrical resistivity and is typical of many types of CO systems.…”

“…In addition, it is well known that the mechanism of electrical conduction in (Ca,R)MnO 3 (R = Ce, Ho, Eu, Sm) is by hopping of polarons [12,16,[24][25][26][27]30]. For conduction to occur, Mn 3+ and Mn 4+ should be the nearest neighbours and the electron jumps from Mn 3+ to Mn 4+ must be via O 2− (i.e.…”

“…Although the focus of interest has mostly rested in the hole-doped manganites Ln 1−x A x MnO 3 (Ln = La-Tb, and A = Ca, Sr, Ba, Pb, etc.) due to their potential applications [1][2][3][4][5][6], many researchers have placed emphasis on electron-doped perovskite manganites with the general formula Ca 1−x Ln x MnO 3 (Ln-rare earth ion) [7][8][9][10][11][12]. One of these oxides that raised enormous interest is Ca 1−x Sm x MnO 3 , where Ca 2+ is partially replaced by the trivalent rare earth cation, Sm 3+ .…”

Effects of Dy and Yb co-doping on thermoelectric properties of CaMnO3 ceramics

“…According to these previous work [15,16], in the Ca 1-2x Dy x Yb x MnO 3 system, Dy and Yb serve as electron doping. And for CaMnO 3 (CMO) phase, the electron doping induces the presence of Mn 3+ within the Mn 4+ matrix [19], and the ionic radius of Mn 3+ (0.64Å) is larger than that of Mn 4+ (0.53Å). So it can be found that the he lattice parameters show an increasing tendency with the increase of dopants.…”

Thermoelectric properties of n-type Ca1−xBixMn1−ySiyO3−δ (x=y=0.00, 0.02, 0.03, 0.04, and 0.05) system

“…Among these n-type materials, the perovskite CaMnO 3 -based compound has been intensively studied due to its relatively low electrical resistivity and large thermopower [6][7][8][9][10][11]. The decrease in the electrical resistivity by means of cationic substitution on the ''A'' site such as R 1Àx A x MnO 3 [8] (R: rare earth cation; A: divalent cation such as Ca, Sr, Ba, and Pb), La 1Àx Sr x MnO 3 [9], Ca 0.98 Gd 0.02 MnO 3Àd [10,11], Ca 1Àx Dy x MnO 2.89 [12], Ca 1Àx La x MnO 3 [13], or on the ''B'' site such as CaMn 1Àx Ru x O 3Àd [14,15], AMn 1Àx Mo x O 3 [15][16][17], Ca 1Àx Dy x Mn 1Ày Nb y O 3Àd [18], results from the adoption of a mixed-valance oxidation state of Mn 3+ /Mn 4+ which modifies the carrier concentration and mobility. Due to their low cost and promising thermoelectric properties, manganites were also investigated as potential candidates for n-type legs in thermoelectric modules [19,20].…”