A simple method for preparing superconducting FeSe pellets without sealing in evacuated silica tubes

Abstract

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Synthesis and Characterization of Molybdenum- and Sulfur-Doped FeSe

“…The mixture was then compressed into pellets (6 mm diameter, 1.5 mm thick, 0.4 g) using a uniaxial pressure of 10 MPa. 22 The Figure 1. X-ray diffraction pattern of (a) FeSe 0.9 and Fe 0.9 Se 0.9 , (b) FeSe 0.9 S 0.1 sample with one-and two-step methods, and (c) Mo 0.1 Fe 0.9 Se 0.9 S 0.1 with 2θ range of 10−90 and (d) TGA curves of the Mo 0.1 Fe 0.9 Se 0.9 S 0.1 and FeSe 0.9 samples.…”

“…With different molar ratios, the powders were mixed together in the agate mortars inside the glove box for more than 30 min. The mixture was then compressed into pellets (6 mm diameter, 1.5 mm thick, 0.4 g) using a uniaxial pressure of 10 MPa . The pellets were sealed inside an evacuated quartz ampoule.…”

“…%, superconductivity was suppressed. , For S-doped FeSe, under high pressure, the critical nematic fluctuations vanish, whereas magnetic order is dramatically induced. , Unlike FeSe under physical pressure, isoelectronic S substitution Se site can tune T s to a nematic critical point (NCP) at x ≈ 0.17 with abrupt change of superconductivity, but no magnetic order appears in FeSe 1– x S x single crystals under ambient pressure. Recently, by simultaneously tuning chemical and physical pressures, a strikingly enhanced T c has been obtained near both ends of the dome-shaped spin density wave (SDW) phase in FeSe 1– x S x rather than near the NCP. − There are many methods for the synthesis of FeSe materials, and these can be divided into four groups: the one step method, the flux method, the high-pressure method, and the solid-state reaction method . The third and last methods are usually used to prepare polycrystalline samples, and the others are used for single crystal preparation. , Generally, it is very difficult to prepare single crystal samples of FeSe with different ratios because of its sensitivity to stoichiometry …”

Stoichiometry of tetragonal and hexagonal FexSe: phase relations

“…In contrast, Grivel [11] demonstrates that short reaction times (e.g. between 1 and 10 h) at temperatures of 400 • C and 700 • C, influence the proportion of other phases formed in addition to β-Fe x Se, the predominant phase.…”

“…between 1 and 10 h) at temperatures of 400 • C and 700 • C, influence the proportion of other phases formed in addition to β-Fe x Se, the predominant phase. Long reaction times up to 100 h reduces the XRD-detectable proportion of other phases such as α-Fe and δ-Fe x Se [11]. In a related study, Guo et al [12] show that the quenching temperature (between 300 • C and 500 • C) results in minimal change in the lattice parameters of β-Fe x Se and has limited affect on T c , (∆ ∼ 0.3 K) .…”