Spark plasma sintering of cobalt ferrite nanopowders prepared by coprecipitation and hydrothermal synthesis.

International audience; Cobalt ferrite exhibits a high coercivity at room temperature and a strong magnetic anisotropy compared to the other spinel ferrites and, consequently appears as an interesting material for permanent magnets and high-density recording. The magnetic properties depend also on the crystallite size. In order to keep the powder properties in a bulk material, dense nanostructured cobalt ferrite has to be sintered. A field activated sintering process like spark plasma sintering (SPS) may be promising for such challenge. The present paper deals with: (i) the preparation of cobalt ferrite by two methods: coprecipitation and hydrothermal synthesis in supercritical water; (ii) …

SPS-assisted preparation of the Magnéli phase WO2.90 for thermoelectric applications

We describe the preparation and simultaneous consolidation of WO2.90 by spark plasma sintering (SPS). SPS allows for the direct manufacturing of large amounts of consolidated material. Synchrotron powder X-ray diffraction indicates that the material is single phase. Microstructure analysis indicates that the pellet is fully dense, allowing high-temperature thermoelectric properties to be reliably measured. The as-prepared samples of WO2.90 reach a ZT of 0.1 at 1100 K.

Sintering of lead phospho-vanadate by spark plasma sintering

International audience

Utilisation de la technique de frittage flash pour la synthèse et la densification d'iodoapatites

Thermoelectric properties of spark-plasma sintered nanoparticular FeSb2prepared via a solution chemistry approach

Nanoparticular FeSb2 was prepared in solution from cyclopentadienyl iron(ii) dicarbonyl dimer [Fe(Cp(CO)2)]2 and antimony nanoparticles. Spark plasma sintering was used as consolidation method to maintain the particle size. The thermoelectric performance of FeSb2 is limited by its high thermal conductivity. In this work, the thermal conductivity was suppressed by nearly 80% compared to the bulk value by introducing grain boundary scattering of phonons on the nanoscale. The thermoelectric properties of the consolidated FeSb2 emphasize the possibility of altering thermal transport of promising thermoelectric compounds by phonon scattering by engineering the interfaces at the nanoscale.

Using crystallographic shear to reduce lattice thermal conductivity: high temperature thermoelectric characterization of the spark plasma sintered Magnéli phases WO2.90 and WO2.722.

Engineering of nanoscale structures is a requisite for controlling the electrical and thermal transport in solids, in particular for thermoelectric applications that require a conflicting combination of low thermal conductivity and low electrical resistivity. We report the thermoelectric properties of spark plasma sintered Magnéli phases WO2.90 and WO2.722. The crystallographic shear planes, which are a typical feature of the crystal structures of Magnéli-type metal oxides, lead to a remarkably low thermal conductivity for WO2.90. The figures of merit (ZT = 0.13 at 1100 K for WO2.90 and 0.07 at 1100 K for WO2.722) are relatively high for tungsten-oxygen compounds and metal oxides in general…

Enhanced thermoelectric properties of the n-type Magnéli phase WO2.90: reduced thermal conductivity through microstructure engineering

The thermoelectric properties of the Magneli phase WO2.90 were investigated, with special attention to how the thermoelectric performance can be altered by changing its microstructure. Spark plasma sintering (SPS) allowed the direct preparation of large amounts of consolidated material. Adding Ta2O5 to the reaction mixture lead to the formation of solid solutions W1−xTaxO2.90via a concurrent reaction between WO3 and Ta2O5 during the SPS treatment. In addition, micron-sized inclusions containing tungsten surrounded by WOx embedded in a WO2.90 matrix were formed, which act as additional scattering centers. As a result, the thermal conductivity of the Ta-containing samples was reduced by ≈30% …