The Effective Properties of Macroscopically Inhomogeneous Ferromagnetic Composites

Snarskiı̆, A. A.; Zhenirovsky, M.

doi:10.1007/978-1-4020-2316-3_60

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“…Partial crystallization of the glasses systematically results in decreases in the α values, which can be attributed to the higher Seebeck coefficients of the precipitated crystalline phases. In addition, effective medium theory applied to the Seebeck coefficient demonstrated that above the percolation threshold of the most conductive phase (which is likely achieved in the present samples), the α values of two-phase materials tend rapidly to that of the most conducting phase. ,− Assuming that this applies in the present case, rough estimates of the Seebeck coefficients of the crystallites for each glass ceramic can be inferred. The Cu 20 As 35 Te 45 and Cu 15 As 30 Te 55 glass ceramics that stabilize the α-As 2 Te 3 and β-As 2 Te 3 crystalline phases, respectively, exhibit α values of 70 and 80 μV·K –1 at 300 K. These results are in fair agreement with the average values of 100 and 150 μV·K –1 measured on pure polycrystalline samples.…”

Section: Results and Discussionmentioning

confidence: 71%

Stabilization of Metastable Thermoelectric Crystalline Phases by Tuning the Glass Composition in the Cu–As–Te System

et al. 2017

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Recrystallization of amorphous compounds can lead to the stabilization of metastable crystalline phases, which offers an interesting way to unveil novel binary or ternary compounds and control the transport properties of the obtained glass ceramics. Here, we report on a systematic study of the Cu-As-Te glassy system and show that under specific synthesis conditions using the spark-plasma-sintering technique, the α-AsTe and β-AsTe binary phases and the previously unreported AsTe phase can be selectively crystallized within an amorphous matrix. The microstructures and transport properties of three different glass ceramics, each of them containing one of these phases with roughly the same crystalline fraction (∼30% in volume), were investigated in detail by means of X-ray diffraction, scanning electron microscopy, neutron thermodiffraction, Raman scattering (experimental and lattice-dynamics calculations), and transport-property measurements. The physical properties of the glass ceramics are compared with those of both the parent glasses and the pure crystalline phases that could be successfully synthesized. SEM images coupled with Raman spectroscopy evidence a "coast-to-island" or dendriticlike microstructure with microsized crystallites. The presence of the crystallized phase results in a significant decrease in the electrical resistivity while maintaining the thermal conductivity to low values. This study demonstrates that new compounds with interesting transport properties can be obtained by recrystallization, which in turn provides a tuning parameter for the transport properties of the parent glasses.

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