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Ca3Co4O9 (349) thermoelectric (TE) ceramics were prepared by hot‐pressing (HP) process under various stress levels up to 30 MPa. Microstructure investigations have revealed strong enhancements of the bulk density and the texture strength, and a remarkable decrease of the in‐plane grain boundary density as the HP stress, σ, is increased. The mechanical properties obtained from nanoindentation and three‐point bending tests, and the TE properties were correlated to the microstructure. The influence of the HP stress level on these properties was examined in the parallel (c) and perpendicular (ab) directions to the pressing axis. Hardness (Hab and Hc ) and elastic modulus (Eab and Ec ) values were shown to increase remarkably with the HP stress level and the anisotropy ratio between out‐of‐plane and in‐plane resistivity values too. As ρab was considerably reduced and the Seebeck coefficient, Sab, remains constant when σ is raised, the power factor, PFab, was greatly improved for the higher stress values. and PFab900 K are 64 and 595 μW.m−1.K−2, respectively, for the HP samples processed under 30 MPa. Thick specimens usable in practical devices were obtained by HP stacked single layers. Their microstructure was investigated and correlated to the TE and mechanical properties.

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Using the spark plasma sintering (SPS) technique, dense nanostructured Ca 0.95 Sm 0.05 MnO 3 (n-type) and textured Ca 3 Co 4 O 9 (p-type) ceramics were prepared. Nanoceramic powders of doped n-type were synthesized using two routes: coprecipitation and solid-state reaction. The SPS method has been used to control the samples' densification and grain growth. Microstructural investigations reveal that the SPS technique results in high bulk density and homogeneous morphology for Ca 0.95 Sm 0.05 MnO 3 , and grain alignment for Ca 3 Co 4 O 9 . The thermoelectric and mechanical properties were investigated, showing a dependence on the starting grain size and being governed by the SPS conditions.

Widespread use of YBa2Cu3O7‐δ (Y123) bulk superconductors as source of strong magnetic fields requires development of high‐performance materials sufficiently reliable with improved thermal transfer ability. An effective approach based primarily on the growth of bulk Y123 single domains comprising a holes‐network to diminish the oxygen diffusion paths is reported here, as well as their progressive annealing at high temperature under oxygen pressure to reduce undue stresses and processing time. Finely, it aims to stimulate the thermal exchange inside the superconductor and compensate for induced magnetic stresses during the field‐trapping process. The approach brings considerable time and energy savings, and turns out to knock down barriers having stymied hitherto the use of Y123 bulk superconductors for engineering applications. Indeed, it enables the achievement of a pore‐free and crack‐free microstructure yielding marked fracture toughness and promoting large size persistent current loops, thereby boosting the trapped field performances. The fostering of the internal thermal exchange leads the maximum trapped field Bmax to shift to higher temperatures by up to 14 K. A value Bmax of 6.34 T is attained at 17 K on ≈16 mm‐diameter reinforced pellet (disk area s = 1.99 cm2), resulting in an outstanding field density Bmax/s=3.19 Tcm−2.

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