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The present study is investigating the effect of high temperature sintering combined with ball milled powders for the preparation of FeSe material via solid state sintering technique. The commercial powders of Fe (99.9% purity) and Se (99.9% purity) were mixed in a nominal ratio Fe:Se = 1:1 and thoroughly ground and ball-milled in a glove box during 6 h. Then, the powder mixture was pressed into pellets of 5 mm in diameter and 2 mm thickness using an uniaxial pressure of 100 MPa. The samples were sealed in quartz tubes and sintered at 600 °C for 24 h. Then, the pellets were again thoroughly ground and ball-milled in the glove box and pressed into pellets, and the final sintering was performed at two different temperatures, namely at 900 °C for 24 h and at 950 °C for 24 h. X-ray diffraction results confirmed that both samples showed mainly of the β-FeSe with tetragonal structure. The temperature dependence of magnetization (M-T) curves revealed a sharp superconducting transition Tc, onset = 8.16 K for the sample sintered at 900 °C. Further, scanning electron microscopy observations proved that samples sintered at 900 °C show a platelike grain structure with high density. As a result, improved irreversibility fields around 5 T and the critical current density (Jc) values of 6252 A cm−2 at 5 K and self-field are obtained. Furthermore, the normalized volume pinning force versus the reduced field plots indicated a peak position at 0.4 for the sample sintered at 900 °C. Improved flux pinning and the high Jc values are attributed to the textured microstructure of the material, produced by a combination of high temperature sintering and ball milling.

We investigated the formation of extended defects in CaFeO2.5, predominantly appearing as antiphase boundaries (APBs), as a function of the synthesis method and temperature. While CaFeO2.5 is known to adopt an ordered oxygen defect structure showing long range order of the (FeO4)∞ chains in its bulk form, interestingly, we demonstrated that the length of these (FeO4)∞ chains can be considerably scaled down to few nanometers by adopting a modified sol–gel method (low temperature synthesis) while the grain size of the resulting nano-phase CaFeO2.5 is around 50 nm. We discuss the synthesis dependent modulation of the length of APBs, characterized by X-ray diffraction and high resolution TEM, to be at the origin of an amplified switching dynamics of the (FeO4)∞ chains. This can accordingly explain the reduction of the onset temperature for oxygen diffusion to set in from 450 °C for bulk-CaFeO2.5 to 320 °C for nano-CaFeO2.5, as determined by 18O/16O oxygen isotope exchange reactions.

Considering the complementary properties of poly(vinylidene fluoride) (PVDF) and poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)], it appears that their blends have the potential to be promising candidates for device applications. We report the evolution of morphology, ferroelectric, and mechanical properties (modulus and hardness) and their dependence on preparation temperature for PVDF–P(VDF-TrFE) blends. From ferroelectric hysteresis measurements it was found that P(VDF-TrFE) rich blends treated at higher temperature show significant values of remanent polarization. Remanent polarization values show a fourfold increase in these P(VDF-TrFE) rich blends treated at higher temperature. Interestingly, blends prepared from high temperature showed greater value of remanent polarization even though they were found to consist of smaller amount of electroactive phase as compared to their low temperature treated counterpart. Nanoindentation experiments revealed that high temperature treatment improves the modulus of blends by at least 100%. This report attempts to tie these findings to the morphology and crystallinity of these blends. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 135, 45955.