Low-temperature synthesis of FeTe_0.5Se_0.5polycrystals with a high transport critical current density

Abstract

Abstract.We have prepared high-quality polycrystalline FeTe 0.5 Se 0.5 at temperature as low as 550°C . The transport critical current density evaluated by the current-voltage characteristics is over 700 A/cm 2 at 4.2 K under zero field, which is several times larger than FeTe 0.5 Se 0.5 superconducting wires. The critical current density estimated from magneto-optical images of flux penetration is also similar to this value. The upper critical field of the polycrystalline FeTe 0.5 Se 0.5 at T = 0 K estimated by Werthamer-Helfand-Hohenberg theory is 585 kOe, which is comparable to that of single crystals. This study gives some insight into how to improve the performance of FeTe 0.5 Se 0.5 superconducting wires.

Solid state synthesis and characterization of bulk FeTe0.5Se0.5superconductors

“…These phases are mainly antiferromagnetic hexagonal FeTe 0.5 Se 0.5 phase (marked with H) and unreacted Fe element (marked as asterisks). We did not detect common impurity phases such as, FeSe 2 , Fe 7 Se 8 and δ-FeSe and also oxide peaks as obtained in previous works by other groups [27,37,38]. The main peaks are indexed as tetragonal FeTe 0.5 Se 0.5 superconducting phase with a space group of P4/nmm, Lattice parameters and unit cell volume of the samples prepared were calculated to be a=3.7885(5) Å, c=5.9453(5) Å and 85.03 Å 3 respectively.…”

“…However, FeTe does not show superconductivity. The other investigation indicates that Se substitution suppressed and causing superconductivity [24][25][26][27]. The FeTe materials can be prepared either in polycrystalline or in single crystal form by using different methods [28][29][30].…”

Enhancement of superconducting properties in FeSe wires using a quenching technique

“…Since the discovery of superconductivity in an iron-based superconducting materials family [1][2][3][4][5] , great efforts have been devoted to the preparation of films [6][7][8] and wires [9][10][11][12][13][14][15] for practical applications. Among these iron-based superconductors, FeSe family such as FeSe, FeTe 1-x Se x and FeTe 1-x S x has several practical advantages over the pnictide.…”

Magneto-optical imaging and transport properties of FeSe superconducting tapes prepared by the diffusion method

“…1(a), which is not consistent with that of the Fe(Te,Se) polycrystals. 17 Although there are no impurity phases in the FeSe tape with a thickness of 25 μm prepared at 800 o C, optical image ( Fig. 1 (b)) indicates the surface of the tape is very rough.…”

“…These images are similar to the MO images of 1111 and low-temperature synthesized FeTe 0.5 Se 0.5 polycrytals. 17,[19][20][21] At all temperatures, bright intensities are restricted in small regions, implying that the intergranular current density is much smaller compared with the intragranular current density. The intragranular current density decreases gradually as the temperature is increased towards T c .…”