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The filamentary (Nd0.33Sm0.33Gd0.33)1.18-Ba2.12Cu3.09Oy (NSG123) superconductors chemically doped with nominal Pt concentrations from 0 to 0.5 at% were fabricated by a solution spinning method. We investigated effects of the amount of Pt addition and cooling rate from partial melting temperature of 1050 degC during OCMG processing on superconducting properties and microstructure of filamentary samples. Pure NSG123 filaments cooled at 20 degC/h-50degC/h showed the Jc vale higher than 2.0 times 104 A / cm2 at 77 K and 0 T. Although the sample treated at fast cooling rate of 60 degC/h exhibited the Jc value of about 3.0 times 103A/cm2 at most, the NSG123 doped with 0.05 at% Pt cooled at 60 degC/h showed high Jc value of 2.0 times 104 A / cm2 at 77 K and 0 T. The field dependence of transport Jc value was also investigated at 77 K for samples cooled at 60 degC/h. The Jc value of 0.8 times 104 A / cm2 was maintained up to magnetic field of 5 T for the 0.05 at% Pt doped sample. The size of (Nd,Sm,Gd)2BaCuO5 particles in NSG123 matrix was reduced from about 3 to 0.5 mum with increasing Pt concentration from 0 to 0.5 at%. In addition, the connectivity in microstructure was improved with increasing Pt concentration. It was found that both Jc-B properties and the microstructure for the sample treated at fast cooling were effectively improved by Pt doping.

(Nd0.33Sm0.33Gd0.33)1.18Ba2.12Cu3.09Oy (NSG123) precursor filaments doped with Al were prepared by a solution spinning method and partially melted at 1050degC for 30 min in flowing 0.1% O2 + Ar gas. Samples were cooled at various rate of 10-60degC/h, and then oxygenated in pure O2 gas. It was found that the microstructural and superconducting properties were strongly influenced on the cooling rate from partial melting temperature to 900degC during OCMG processing. Although the sample without Al cooled at 20-50degC/h showed Jc value higher than 2.0 times 104 A / cm2 at 77 K and 0 T, the sample treated at fast cooling rate of 60degC/h exhibited the Jc value of about 3.0 times 103 A / cm2 at most. In contrast, the NSG123 doped with 0.05 at%Al even at a rate of 60degC/h cooling showed high Jc value of 1.5 times 104 A / cm2 at 77 K and 0 T, and exhibited a well aligned texture and a dense microstructure. From Jc measurements in applied magnetic fields, a Jc value higher than 103 A / cm2 was maintained up to 9 T for 0.05 at % Al doped filament. It was found that a small amount of Al doping into NSG123 was effective on refinement of the size of the NSG211 particle and reduction pores and cracks in microstructure for sample treated even at fast cooling, and thereby increased Jc values.

The effect of the starting composition on the superconducting properties for ternary system (Nd, Sm, Gd)–Ba–Cu–O filaments was systematically investigated. The filaments with the composition of (Nd 0.33 ,Sm 0.33 ,Gd 0.33 ) 1.18 Ba 2.12 Cu 3.09 O y (sample A), (Nd 0.50 ,Sm 0.25 ,Gd 0.25 ) 1.18 Ba 2.12 Cu 3.09 O y (sample B), (Nd 0.25 ,Sm 0.50 ,Gd 0.25 ) 1.18 Ba 2.12 Cu 3.09 O y (sample C) and (Nd 0.25 ,Sm 0.25 ,Gd 0.50 ) 1.18 Ba 2.12 Cu 3.09 O y (sample D) were prepared by a solution spinning method. All samples partially melted at temperature range of 1030–1080 °C in flowing 0.1% O 2 + Ar exhibited J c value higher than 10 4 A/cm 2 at 77.3 K and self-field. Among these samples, the best transport J c value of 7.2 × 10 4 A/cm 2 was attained in sample B with Nd-rich composition. The field dependence of transport J c value was also examined at various temperatures between 77.3 K and 90 K in applied magnetic fields up to 17 T. In the case of samples A, the J c value gradually decreased with increasing the applied magnetic field, and the J c value of 2.4 × 10 3 A/cm 2 at 77.3 K was maintained up to high magnetic fields of 17 T. On the contrary, the J c value of sample B decreased with increasing the applied magnetic field and the superconductivity disappeared at about 15 T. It was found that the three element ratio in NSG123 contributed to flux pinning in a different manner and affected in J c behavior in magnetic field.

Filamentary Gd-Ba-Cu-O superconductors doped with nominal Zr concentrations between 0 and 0.5 at% relative to Gdl23 were prepared by a solution spinning method. Samples were partially melted in flowing 20% O2 + Ar atmosphere gas at various partial melting temperatures and oxygenated in pure oxygen gas. High Jc value of 2 times 104 A/cm at 77 K and 0 T were obtained for the Gd123 + 0.1at%Zr sample optimally processed. In the case of doping levels less than 0.5 at %, Tc values, which were about 92 K with sharp transitions, were hardly influenced by Zr concentration. From transport critical current measurements in magnetic fields, the Jc value of the pure Gd123 filament sharply decreased with increasing applied field. Gd123 with 0.5 at%Zr doping processed under optimum conditions showed little deterioration of Jc values in low magnetic fields and Jc values higher than 103 A/cm was maintained up to 14 T. It was also found that Jcs in high magnetic field and the irreversibility field were improved by a small amount of Zr doping.

Precursor filaments with starting composition (Nd0.33,Sm0.33,Gd0.33) : Ba : Cu = 1.18 : 2.12 : 3.09 were prepared by a solution spinning method. Samples were partially melted at temperature range of 1020-1090degC in flowing 0.1%O2 + Ar, 1%O2 + Ar and 20%O2 + Ar and then oxygenated in pure 100%C>2 gas. The Tc value decreased from 91.3 K to 88.8 K with increasing oxygen concentration in atmosphere gas. A transport Jc value higher than 104 A/cm at 77 K and 0 T was showed over a wide temperature range of 1030-1080degC in 0.1%O2 + Ar and 1040-1090degC in 1%02 + Ar. Especially, the 0.1%O2 + Ar sample partially melted at 1050degC and the 1%02 + Ar sample at 1060degC exhibited the highest Jc value of 2.7 x 104 A/cm2 and 2.5 x 104 A/cm2, respectively. The transport Jc value of the sample melted in flowing 0.1%O2 + Ar was maintained higher than 2.4 x 103 A/cm2 at 77 K in applied magnetic fields up to 17 T. On the other hand, the maximum Jc value at 77 K and 0 T for the sample treated in 20%O2 + Ar melted at 1080degC showed 5.4 X 103 A/cm2 at most, and the superconductivity was disappeared at magnetic field of 7 T.

The effect of Zr and Zn doping on superconducting properties and microstructures of filamentary Eu–Ba–Cu–O superconductors prepared by a solution spinning method has been investigated. Samples doped with small amounts of Zr and Zn showed relatively high Jc values of around 2 × 104 A cm−2 at 77 K and 0 T, which was two times larger than that of the pure Eu123 filament. The temperature range for the partial melting in reduced oxygen partial pressure obtained the Jc value higher than 104 A cm−2 at 77 K became wider when Zr and Zn were added. From the SEM observation, a small amount of Zr and Zn doping was found to be useful to reduce the size of Eu211 particles, whereas it showed adverse effects on the dispersion of Eu211 particles and compositional homogeneity in a Eu123 matrix. In the case of Zn doping, although sample showed high Jc value larger than 104 A cm−2 at magnetic field lower than 2 T, a Jc value monotonically decreased at above 3 T and superconductivity was disappeared at 11 T. On the contrary, in spite of the fact that a Jc value of sample with 0.5 at.% Zr decreased by applying only a magnetic field of 0.2 T, superconductivity could be maintained up to 17 T at 77 K.

(Nd 0.33 Sm 0.33 Gd 0.33 ) 1.18 Ba 2.12 Cu 3.09 O y filaments have been successfully fabricated by a solution spinning method and OCMG processing. We have systematically investigated the relationship between cooling rate from the partial-melting temperature and transport J c value for filamentary samples treated in 0.1%O 2 + Ar. It was found that both the J c value and the microstructure of samples depended on the cooling rate. The samples partially melted at 1050°C and cooling rate of 10–50 °C/h showed J c value higher than 10 4 A/cm 2 . The maximum J c value of 3.0 × 10 4 A/cm 2 was obtained for 40 °C/h sample. The transport J c was also measured at 83–90 K in external magnetic fields up to 17 T. The 10 °C/h sample exhibited superior J c behavior and a J c value of 1.1 × 10 3 A/cm 2 at 83 K was maintained up to 17 T, in which fine (Nd,Sm,Gd) 2 BaCuO 5 particles about 1 μm in diameter were homogeneously dispersed.

High- T c screen-printed Ho–Ba–Cu–O films were prepared on YSZ substrates by a melt processing method. The films were fired at T s = 1000–1050 °C for 5 min and cooled to 450 °C by two steps in flowing O 2 . The maximum critical current density J c (77 K, 0 T) of 2.0 × 10 3 A cm − 2 was only attained under much limited firing conditions; T s = 1020 °C and cooled to 800 °C at a cooling rate of 400 °C h − 1 .

Dy-Ba-Cu-O filaments have been successfully fabricated by a solution spinning method. The relationship between the partial melting temperature and the transport Jc value at 77 K of the filamentary sample was systematically investigated. Two kinds of precursor filaments with starting composition of Dy:Ba:Cu = 1.18:2.12:3.09 (sample A)and Dy:Ba:Cu = 1.00:2.00:3.00 (sample B) were partially melted in 1%O2 + Ar atmospheric gas and oxygenated in pure 100% O2 gas. Samples partially melted at a wide temperature range of 990-1040 ?C had Jc values higher than 104 A/cm2. Both sample A and sample B partially melted at 1020 ?C exhibited the maximum Jc value higher than 4.2 ? 104 A/cm2 and 2.0 ? 104 A/cm2, respectively. These samples had a dense microstructure consisting predominantly of Dy123 and finely dispersed Dy211 particles. The Dy211 particles with a diameter of about 1?m were finely dispersed in sample A, while the particles with a diameter of about 5?m were observed in sample B. The Jc values of both samples were maintained about 2.0 ? 103 A/cm2 up to 14 T.

The effect of Zr and Zn doping on transport critical current density and microstructure of filamentary Dy-Ba-Cu-O superconductor was investigated. Precursor filaments prepared by a solution spinning method were partially melted in atmosphere gas and oxygenated. Samples doped with Zr and Zn showed dense microstructure, and finely dispersed Dy2BaCuO5 particles in the Dy123 matrix were observed. It was found that the superconducting properties of Dy123 filaments doped with Zr and Zn were strongly dependent on the heating condition and the atmosphere. A high Jc value more than 104 A/cm2 with good reproducibility was obtained when these samples partially melted in flowing 20%O2 + Ar gas. By controlling the heat treatment condition, the maximum Jc value of 2.7 × 104 A/cm2 at 77 K and self-field were attained for the sample doped with 0.1 at % Zr. In the case of the sample doped with 0.1 at % Zn, the Jc value around 2.5 × 104 A/cm2 was obtained, which was comparable with that of sample without doping. The relation between the field dependence of Jc and microstructure of the filamentary sample was also examined.

Carbon nanohorn (CNH) doping in MgB 2 wire prepared by suspension spinning was studied to enhance flux pinning. The mixed powders of MgB 2 and CNH with nominal composition of (MgB 2 ) 0.95 C 0.05 were suspended in a mixed poly(vinyl alcohol) solution. The as-drawn filaments were hot-pressed under 20 MPa at 200 °C for 8 h. The samples were enveloped by an iron sheet with a pellet of mixed powder of Mg and B and vacuum-sealed in a fused quartz tube, and then sintered at the temperature ranging from 885 °C to 900 °C for 2–3 h. The superconductivity of the samples was studied by electrical resistivity and SQUID method. Serious deterioration of T c was not observed for the doped sample. The CNH doping resulted in enhancement of the transport J c values at 4.2 K in high fields ranging from 6 T to 10 T by sintering at 885 °C for 2 h. The superconductivity at 4.2 K was maintained by applying the field of 14 T for the doped sample sintered at 900 °C for 3 h.

Precursor filaments of Dy-Ba-Cu-O super-conductor were prepared by a solution spinning method and partially melting in an atmosphere gas with various oxygen concentrations. It was found that the transport Jc value at 77 K and 0 T of the filamentary sample was strongly dependent on the partial-melting temperature and gas atmosphere. The samples partially melted under flowing 1%O/sub 2/+Ar gas exhibited Jc values larger than 10/sup 4/ A/cm/sup 2/ over a wide temperature range of 980-1040/spl deg/C and a dense microstructure. The filamentary sample with the starting composition of Dy:Ba:Cu=1.18:2.12:3.09 treated at 1020/spl deg/C under flowing 1%O/sub 2/+Ar showed a transport Jc value greater than 4.3/spl times/10/sup 4/ A/cm/sup 2/ at 77 K and 0 T, and the Jc value of 2.0/spl times/10/sup 3/ A/cm/sup 2/ was maintained up to the magnetic fields of 14 T. The samples partially melted in 20%O/sub 2/+Ar gas and 100%O/sub 2/ gas showed relatively low Jc value of 6.0/spl times/10/sup 3/ A/cm/sup 2/ and 1.2/spl times/10/sup 2/ A/cm/sup 2/ at most.

The filamentary Sm123 precursor was prepared by a solution spinning method. The precursor was partially melted in flowing 0.1%O 2 + Ar and 1%O 2 + Ar. The transport J c value for the filamentary Sm123 superconductors was examined at 77 K in applied magnetic fields up to 10 T. The J c value higher than 10 4 A/cm 2 was maintained up to 4 T for the samples melted in flowing 1%O 2 + Ar. The J c value gradually decreased with increasing applied magnetic fields from 4 to 6 T and the superconductivity rapidly deteriorated by applying the fields above 8 T. On the contrary, the J c values drastically decreased for the samples melted in flowing 0.1%O 2 + Ar by applying the fields higher than 1 T, and the superconductivity at 77 K was disappeared around 4 T.

YBCO films of approximately 7–8-μm thickness on YSZ substrate were fabricated by spraying a suspension consisting of YBCO powders. The film with 10 wt.% Ag fired at 920°C showed relatively high J c values of approximately 3.3×10 3 Acm −2 (77 K, 0 T) as compared to approximately 1.0×10 3 Acm −2 for the undoped films.

Nd-Ba-Cu-O thick films were fabricated onto (100) YSZ substrates by screen printing method. Two kinds of powders with different nominal compositions were used to form the ink for printing. In order to supress film-substrate interaction, the printed films were fired at relatively low temperature of Ts=990°C in various kinds of gases; Ar, Ar+0.1%O2, Ar+3%O2 and N2. After being fired at Ts for 5min, the films were cooled from Ts to 500°C by two steps. The superconducting properties of the films were found to strongly depend on the preprocessed powder for ink, the kind of flowing gas and the cooling conditions. The film, which was cooled rapidly from Ts to 890°C at a rate of 400°C/h and then cooled to 500°C at a rate of 50°C/h in Ar+0.1%O2, showed relatively a high Jc value of about 500 A·cm-2 (77K, 0T).

Y1Ba2Cu3Ox films of about 50–60 μm thickness on Ni substrates were fabricated by spraying a suspension consisting of YBCO powders. The films which were fired under flowing argon and then annealed in oxygen showed relatively high Jc values of about 500 A/cm2 (77 K, 0T) over a firing temperature range from 910–950°C. When the films were fired at 960°C, the Ni whose concentration was about 4 at.% and large-size cracks were found to be present on the surface of the film, resulting in the destruction of the superconducting properties of the film. The reaction products produced near the interface regions and on the surface of the films were also studied.

Y 1 Ba 2 Cu 3 O x films, ranging in thickness from 1.5 to 7.5 μm, on (100) YSZ substrates were fabricated by spraying a suspension consisting of YBCO powders. The films were sintered at 940°C for 2 min under flowing argon and then exposed to oxygen. It was found that the spraying conditions such as the flow rate of carrier gas and the aperture of spray nozzle had a great influence on both the mechanical and the superconducting properties of YBCO films. The maximum critical current density J c (77 K) of about 4200 A cm − 2 was obtained by reducing the droplet size.

YBCO films of 3–5 μm thickness were fabricated on YSZ substrate by spray atomization and deposition technique. The films that were sintered at 930–945°C under flowing argon and then annealed in oxygen showed relatively high Jc values of about 2–3×103 A cm−2 (77 K, 0T).

The improvement of the critical current density Jc of YBCO thick films has been attempted by adding BaSnO3 powder and ultrafine Sn particles, whose diameter is about 2 μm and 7 × 10−2 μm, respectively. It was found that the addition of a small amount of these particles was effective for the enhancement of Jc of thick films prepared by a liquid-phase processing method. The 1 wt.% BaSnO3 films fired at Ts = 1040−1060°C and the 3 wt.% Sn films (Ts = 1030−1060°C) showed Jc values (77 K, 0 T) of about 2.1−2.4 × 103 Acm−2 and 3.1−3.5 × 103 Acm−2, respectively, as compared to 2.0 × 103 Acm−2 for the undoped films.

The transport J c for filamentary Eu123 superconductors prepared by a solution spinning method was examined at 77 K in magnetic fields up to 10 T. The samples which partially melted under flowing 0.1%O2+Ar and 1%O2+Ar had a well-aligned structure along the filament diameter as well as the length. Excellent behavior in the field dependence of J c was detected for the filamentary Eu123 superconductors which partially melted in flowing 0.1%O2+Ar. Significant angular dependence along the diameter of the J c value was not detected and a high J c value of around 104 A/cm2 at 77 K and 10 T was maintained.

Y-Ba-Cu-O.Ag metal mixed thick films were prepared on YSZ substrates by the screen-printing technique. It was found that the addition of fine Ag particles greatly enhanced the superconducting property of the films.