Smart meta-superconductor MgB2 constructed by the dopant phase of luminescent nanocomposite

Abstract

On the basis of the idea that the injecting energy will improve the conditions for the formation of Cooper pairs, a smart meta-superconductor (SMSC) was prepared by doping luminescent nanocomposite Y2O3:Eu3+/Ag in MgB2. To improve the superconducting transition temperature (TC) of the MgB2-based superconductor, two types of Y2O3:Eu3+/Ag, which has the strong luminescence characteristic, with different sizes were prepared and marked as m-Y2O3:Eu3+/Ag and n-Y2O3:Eu3+/Ag. MgB2 SMSC was prepared through an ex situ process. Results show that when the dopant content was fixed at 2.0 wt.%, the TC of MgB2 SMSC increased initially then decreased with the increase in the Ag content in the dopant. When the Ag content is 5%, the TC of MgB2 SMSC was 37.2–38.0 K, which was similar to that of pure MgB2. Meanwhile, the TC of MgB2 SMSC doped with n-Y2O3:Eu3+/Ag increased initially then decreased basically with the increase in the content of n-Y2O3:Eu3+/Ag, in which the Ag content is fixed at 5%. The TC of MgB2 SMSC doped with 0.5 wt.% n-Y2O3:Eu3+/Ag was 37.6–38.4 K, which was 0.4 K higher than that of pure MgB2. It is thought that the doping luminescent nanocomposite into the superconductor is a new means to improve the TC of SMSC.

Reinforcing Increase of ΔTc in MgB2 Smart Meta-Superconductors by Adjusting the Concentration of Inhomogeneous Phases

“…The optimal doping concentrations for a MgB 2 , b MgB 2 , and c MgB 2 were 0.5%, 0.8%, and 1.2%, respectively. The corresponding ΔT cs were 0.4 K, 0.9 K, and 1.2 K, which exhibit significant improvements compared with the ΔT cs (0.2–0.4 K) in previous work [ 36 , 37 , 38 , 39 , 40 ]. Such an improvement of T c is a novel property given that all the experiments before our work confirmed that doping a second phase decreased the T c of MgB 2 .…”

“…The results obtained in these studies show that unlike conventional chemical doping, which consistently reduces the T c of MgB 2 , the SMSC method of doping EL materials could help increase the T c of MgB 2 . The same conclusions were drawn from substituting the inhomogeneous phase with YVO 4 :Eu 3+ or luminescent nanocomposite Y 2 O 3 :Eu 3+ /Ag [ 39 , 40 ] and replacing MgB 2 with Bi(Pb)SrCaCuO [ 41 , 42 ]. The effectiveness of improving the T c of superconducting materials through the SMSC method by doping with EL inhomogeneous phases has been proven, but the ΔT c ( ΔT c = T c − T cpure ) values obtained are generally small (0.2–0.4 K).…”

“…Φ a , Φ b , and Φ c refer to the particle sizes of a MgB 2 , b MgB 2 , and c MgB 2 powders, which will be described in detail at the experiment section. The brown hexagons represent the MgB 2 particles, and the gray dashed lines represent the flakes of inhomogeneous phase with the surface size of approximately 20 nm and thickness of approximately 2.5 nm [ 40 , 45 ]. The flakes of Y 2 O 3 , Y 2 O 3 :Sm 3+ , Y 2 O 3 :Eu 3+ , and Y 2 O 3 :Eu 3+ /Ag mainly gather on the surfaces of the MgB 2 particles as shown in Figure 1 d. Figure 1 e–h present the schematics of Y 2 O 3 , Y 2 O 3 :Sm 3+ , Y 2 O 3 :Eu 3+ , and Y 2 O 3 :Eu 3+ /Ag, respectively.…”

“…The external field added during the measurement of the T c of SMSC with a four-probe method can excite the inhomogeneous phases to generate EL, achieving the purpose of strengthening the Cooper pairs, resulting the change of T c in macroscopic. A SMSC is a material whose T c can be adjusted and improved by the stimulus of external field, which is a new property and cannot be achieved by traditional doping with a second phase [ 36 , 37 , 38 , 39 , 40 , 41 , 42 ]. Our group subsequently conducted a series of studies, mainly using MgB 2 as the base superconducting material and Y 2 O 3 :Eu 3+ as the base EL material [ 36 , 37 , 38 ].…”

Relationship between the TC of Smart Meta-Superconductor Bi(Pb)SrCaCuO and Inhomogeneous Phase Content

“…The results showed that the doping of Y 2 O 3 :Eu 3+ EL materials increases the T C of MgB 2 . We believe that the Y 2 O 3 :Eu 3+ materials generate an EL under the action of an external electric field and that EL energy injection promotes the formation of Cooper pairs; the T C of MgB 2 is improved via EL [ 35 , 36 , 37 , 38 , 39 ]. At the same time, a smart meta-superconductor B(P)SCCO consists of the B(P)SCCO matrix and an inhomogeneous phase Y 2 O 3 :Eu 3+ or Y 2 O 3 :Eu 3+ +Ag was constructed in BSCCO superconductors.…”