Lattice parameters and cell volume of the CaMn1− x W x O3−δ (0.00 ≤ x ≤ 0.05) series plotted against the nominal W content (xnom ).
X-ray photoemission spectrum of the CaMn1− x W x O3−δ (0.00 ≤ x ≤ 0.05) series. Shown are the W 4f7 / 2 (BE = 36.0 eV) and W 4f5 / 2 (BE = 38.7 eV) intensities. The inset shows the dependence of observed x obs from the nominal x nom tungsten content.
Scanning electron microscopy image of a sintered CaMn1−xWxO3−δ (x = 0.03) sample. The sample is representative for all substitution levels.
Time dependent in situ thermo-gravimetric analyses of the oxygen loss and uptake of CaMn1− x W x O3−δ (x = 0.01) under heating and cooling cycles that simulate those used in transport measurements: (a) a powder sample and (b) a bar-shaped sample (as used for transport measurements). The figure depicts the plateau at T = 1205 K for both the heating and cooling cycles.
Temperature dependent in situ thermo-gravimetric analyses of the oxygen loss and uptake of CaMn1− x W x O3−δ (0.00 ≤ x ≤ 0.04) on powder samples. Oxygen loss is delayed with increasing tungsten substitution.
Transport properties of the CaMn1−x W x O3−δ (0.00 ≤ x ≤ 0.05) series as function of the temperature. (a) Logarithmic plot of the electrical resistivity. The inset shows a linear plot of the resistivity (ρ) for 0.03 ≤ x ≤ 0.05. (b)Seebeck coefficient (S): Absolute values decrease with substitution level. (c) Power factor S2ρ−1.
Transport properties the CaMn1−x W x O3−δ (0.00 ≤ x ≤ 0.05) series plotted against the reciprocal temperature (T −1) The graphs are evaluated in the static oxygen region below T = 800 K, which corresponds to T −1 = 0.00125 K−1. (a) The action energy Ea of the electrical conductivity is derived from the slope of the ln(ρ/T) plot. (b) The action energy E s of the Seebeck effect is equal to the slope of the Seebeck coefficient plot. Both energies are presented in Table III .
Seebeck coefficient of the series CaMn1−x W x O3−δ (0.00 ≤ x ≤ 0.05) plotted against ln((1 − y)/y). [Mn3+] (y ≈ [Mn3+]) is derived from W content and O deficiency. m represents the slope m = dS/d(ln((1 − y)/y)). (a) Constant temperature, stable oxygen content, variable W content. (b) High-temperature oxygen-deficient region. Constant W content, variable temperature, and oxygen deficiency.
Thermal conductivity and figure-of-merit ZT of the series CaMn1−x W x O3−δ (0.00 ≤ x ≤ 0.05): (a) Lattice and electrical part of the thermal conductivity. (b) Total thermal conductivity. The inset shows a representative DSC measurement at different ramping rates (5–20 K/min). Heating is red, cooling is blue. (c) Figure-of-merit ZT.
Structural parameters after LeBail fitting and observed densities of the series CaMn1− x W x O3−δ (0.00 ≤ x ≤ 0.05). Relative densities are calculated according to theoretical density derived from the cell volume and the molecular formula.
Elemental composition, heat capacity, and phase-transition temperatures of the CaMn1−x W x O3−δ (0.00 ≤ x ≤ 0.05) series.
Electronic transport properties of the CaMn1−x W x O3−δ (0.00 ≤ x ≤ 0.05) series.
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