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Effects of time and temperature of firing on Fe-rich ceramics studied by Mössbauer spectroscopy and two-dimensional 1H-nuclear magnetic resonance relaxometry
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Image of FIG. 1.
FIG. 1.

RT Mössbauer spectra for the unfired reference sample R0[0 h] (a) and for R700[0 h] (b), R850[0 h] (c), and R1000[0 h] (d).

Image of FIG. 2.
FIG. 2.

Changes with firing temperature at tsoak = 0 h for (a) relative areas of the 57Fe spectrum components: site A (open circles), site B (open squares), and hematite (open triangles), and (b) the HFD of the magnetic sextet of hematite.

Image of FIG. 3.
FIG. 3.

Changes with firing temperature evolution for the weighted values of the isomeric shift δ (a) and the quadrupole splitting Δ (b) of paramagnetic Fe(III) for samples fired at soaking times of 0 h (closed symbols) and 10 h (open symbols).

Image of FIG. 4.
FIG. 4.

Effect of soaking time on the HFDs for T = 1000 °C (a) and on the low magnetic-field (LB) relative areas for T = 900 °C (open circles), T = 1000 °C (open squares), and T = 1100 °C (open triangles) (b).

Image of FIG. 5.
FIG. 5.

T1-T2 spectra for iron-rich ceramics fired at temperatures between 600 and 1100 °C and soaking times of 0 h, 1 h, 5 h, and 10 h. The gray-scale contours are equally spaced from 20% (light gray contour) to 90% (black contour) of the maximum intensity for each map. The dash-dotted line indicates the T1 = T2 condition, while the solid line indicates T1 = λT2, where λ is the value of T1 p/T2 p for the main peak, as shown in the box in the upper left of each figure. In the R1100[10 h] map, three peaks are discernible at λ = 270, 39, and 10, in order of increasing T2.

Image of FIG. 6.
FIG. 6.

P(T 1,T 2)-distributions for the R1100[5 h] (a) and R1100[10 h] (b) samples processed with the appropriate αOPT values of 1.3 and 3.3, respectively, and with α = 10 and α = 100. Data are presented as in Fig. 5.

Image of FIG. 7.
FIG. 7.

T1 − T2 spectra for the R1100[10 h] sample, measured using 2τ = 44 μs, 60 μs, and 80 μs. Data are presented as in Fig. 5. For the T1−T2 distribution taken at the shortest echo time, three peaks are discernible and their T1 p/T2 p-values are reported on the plot.

Image of FIG. 8.
FIG. 8.

Distribution of T1/T2 ratio obtained by integrating the 2D spectrum for T = 800 °C (top), T = 900 °C (center), and T = 1100 °C (bottom) series of samples measured at 0 mm (open symbols) and 3 mm (full symbols). Within each plot, the signal density distributions are separately normalized to the maximum intensity of the corresponding T1−T2 measurement. T1/T2-values < 1 are not physically acceptable and are caused by artifacts in the Laplace inversion.

Image of FIG. 9.
FIG. 9.

Firing temperature dependence of the percent area of the hematite sextet in the Mössbauer spectrum (closed triangles) and of the reciprocal of the logarithmic mean of the longitudinal (open squares) and transverse (open circles) relaxation times for the samples fired at zero soaking time. Both y-scales are logarithmic and cover the same number of orders of magnitude.

Image of FIG. 10.
FIG. 10.

Percentage area of the hematite sextet (a) and logarithmic mean of the transverse relaxation rate (b) vs. firing temperature. Data presented for all soaking times investigated: 0 h (empty circles), 1 h (crossed circles), 5 h (circled dots), and 10 h (filled circles). For the sake of clarity, the Fe2O3 content curves at tsoak values of 1 h and 10 h are displayed with slightly shifted firing temperature values. The error in to the hematite fraction estimate is 5%, and the relative uncertainty for the 1/T2 LM-values is also 5%.


Generic image for table
Table I.

Mössbauer parameters for the samples fired at 900, 1000, and 1100 °C for various soaking times. BC and AC are the values relative to the magnetic hyperfine field and to the relative area obtained by fitting of HFD curves.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Effects of time and temperature of firing on Fe-rich ceramics studied by Mössbauer spectroscopy and two-dimensional 1H-nuclear magnetic resonance relaxometry