Characterization of low-temperature synthesized FeCr0.05Se superconductors

• FeCr0.05Se samples were synthesized at various low temperatures.
• The 450 °C sintered sample had the utmost content of β  -FeSe phase. The Tconset of 450 °C sintered sample reached a maximum.
• The edge size of stratified crystal became wider when the synthesized temperature reached as high as 550 °C.

Polycrystalline samples of FeCr0.05Se were synthesized by solid-state reaction using the two-step sintering method to study the effects of various low temperatures on the microstructure and superconductivity in this system. These synthesis temperatures have been established by optimization. Electrical resistivity measurements confirmed that superconducting transition temperature Tconset reached a maximum of 10.2 K at 450 °C as β  -FeSe phase content reached the maximum under this condition. As the sintering temperature increased, the partial substitution of Cr by Fe caused an enhancement of lattice parameters, and consequently Tconset was much higher at 550 °C than at 400 °C, though the amounts of β-FeSe were appropriately the same in these two samples.