Structural and magnetic phase diagram of the two-electron-doped(Ca1−xCex)

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.…”

Synthesis and electrical properties of nanocrystalline Ca1−xEuxMnO3±δ (0.1≤x≤0.4) powders prepared at low temperature using citrate gel method

“…Although in previous works [11,13,20] the Ca 1 − x Eu x MnO 3 system for different x values was indexed as an orthorhombic Pnma space group, our results for 0.3 ≤ x ≤ 0.4 present a poorer overall fit considering this space group. Based on some published works [17,32,33] attempts to refine the XRD data with the monoclinic space group P21/m (which is a subgroup of Pnma) allow us to improve the fittings for 0.3 ≤ x ≤ 0.4. In fact, the roomtemperature structure for similar samples of [32] as monoclinic P21/m symmetry.…”

Electron transport in CaMnO3 − δ at elevated temperatures: a mobility analysis

“…Substitution of calcium for higher-charged cations and formation of vacancies in the oxygen sub-lattice both result in partial reduction of Mn 4+ to Mn 3+ cations and appearance of n-type conductivity [1][2][3][4][5][6]. The electrondoped derivatives Ca 1−x R x MnO 3−δ , where R is a rare earth metal, are stable in different atmospheres and exhibit rather large values of conductivity (σ) and negative thermopower (S) up to 1000°C.…”