During the sintering process of Ag-alloy sheathed Bi-2223 tapes, post-annealing (PA) played an important role on the final current capacity by forming a Pb-rich phase named (Pb,Bi)3Sr2Ca2CuOx (3221) and healing the cracks. Due to the different oxygen penetration rate between AgAu alloy and pure Ag, which is traditionally used in other Bi-2223 tapes, the influence of PA parameters on the 3221 phase content, microstructures, and current capacity of AgAu tapes should be systematically studied. In this study, PA processes with different temperatures of 770–800 °C have been performed on fully reacted 37-filamentary (Bi, Pb)-2223/AgAu tapes in the atmosphere of 7.5% O2 balanced with Ar. It is found that the 3221 phase appeared after PA with its amount first increasing then decreasing with increasing PA temperature. The critical temperature Tc and peak temperature (Tp) obtained with AC susceptibility measurement both increased with increasing PA temperature, and reached the maximum value at 780 °C then decreased with increasing PA temperature. Due to the improvement of Tc and intergrain connectivity, the critical current density (Jc) increased by 24% after PA at 780 °C. Meanwhile, the 3221 phase formation mechanism has also been systematically discussed by varying the amount of remnant liquid in tapes in HT1 process.

Oxygen partial pressure was the key factor to tune the phase evolution mechanism of Bi-2223 system. In order to investigate the influence of packing atmosphere on the phase formation rate of Bi-2223, microstructures‚ and the current capacity of final tapes‚ 37-filamentary Bi-2223/AgAu tapes were fabricated by powder-in-tube (PIT) process, and the powder packing process operated in the glove box under different atmosphere of pure O2‚ air, and N2–7.5%O2, with the oxygen partial pressure of 100%‚ 25%, and 7.5%, respectively. With different packing atmosphere, the phase formation rate of Bi-2223 increased obviously during the first heat treatment process (HT1). While, based on the same HT1 process, the maximum Bi-2223 phase content was obtained in the tapes with packing atmosphere of N2–7.5%O2‚ which should be attributed to the suitable Bi-2223 content and distribution. Due to the improvement of superconducting phase content and better texture structure, the critical current density increased with decreasing oxygen partial pressure of packing atmosphere and the maximum value of 19.9 kA/cm2 was reached. Moreover‚ the in-field current capacities of these Bi-2223/AgAu tapes have also been enhanced with low oxygen partial pressure in packing atmosphere, attributed to the improvements of intergrain connectivity.

Monofilament AgAu sheathed Bi-2223 tapes were fabricated by powder in tube (PIT) process. The influences of cooling rate during the second heat treatment process (HT2) on the phase composition, microstructures and transport properties of Bi-2223/AgAu tapes were investigated. Results show that after the HT2 process, the content of Pb-rich Pb3Sr2.5Bi0.5Ca2CuOy, (3321) phase increases with the decreasing cooling rate, while the size of CuO phase particles becomes bigger. With the cooling rate decreasing from 600 degrees C/h by 1 C/h, the critical current density J(c) increases from 7 kA/cm(2) to the maximum value of 11.5 kA/cm(2), which increases by 64%. Meanwhile the current capacities in magnetic field of these Bi-2223/AgAu tapes have also been enhanced with slow cooling process, attributed to the improvements of both the intergrain connectivity and the flux pinning properties.

Monofilament and 37-filamentary Bi-2223 tapes were fabricated by powder in tube (PIT) process. And the mono-filamentary wires were drawn from ϕ12mm to hexagon 1.51 mm with one and three times intermediate annealing, respectively. The influences of different intermediate annealing times on the core density, morphology and transport properties of Bi-2223 wires and tapes were systematically investigated. It was noticed that the density and the Vickers micro-hardness values of superconducting core on the cross-section of one time annealing wires were higher than those of three times annealing wires. Meanwhile, it was observed that the Ag/oxide core interfaces of the wire with one time annealing were more smooth than those of the three times annealing wire. With the intermediate annealing time decreasing from three to one, the critical current density Jc increased from 17.9 kA/cm2 to 20.5 kA/cm2. And the enhancement of Jc-B properties suggests the improvement of intergrain connections due to the increasing core density. Meanwhile one time annealing procedure was used to Ag-Au sheathed tape, Jc reached 16.3 kA/cm2, this value was also higher than those traditional wires in our previous experiments, which suggests that the decreasing of annealing times during drawing process is also effective in AgAu sheath tapes for the enhancement of current capacity.

Thirty-seven-filamentary AgAu-sheathed Bi-2223 tapes were fabricated by a powder-in-tube (PIT) process. And, the round wires ( ϕ 1.86 mm) were rolled to 0.35-mm tapes with 12, 7, 5, and 4 rolling passes through flat rolling, respectively. The influences of different rolling passes on the core density, deformation, and transport properties of Bi-2223/AgAu tapes were systematically investigated. It was noticed that after rolling, the Vickers microhardness of the superconducting core and deform homogeneity along both the horizontal and vertical directions on the cross section of seven-pass rolled tape were better than those on the tapes with other passes, which proved the larger core density and uniform deformation with the seven-pass rolling process. Meanwhile for the wires with 12 and 7 passes, the AgAu/superconducting core interfaces were much flatter. With the rolling passes decreasing from 12 to 4, the critical current density ( J c ) first increased and then decreased. Due to the better homogeneity and flatter interfaces, J c reached the maximum value of 17.3 kA/cm 2 on the seven-pass sample. Meanwhile, the enhancement of current capacities in magnetic field applied parallel to the Bi-2223/AgAu tape surface could also be recognized as the evidence of improving intergrain connections due to the higher density in seven-pass rolled tapes.

Coated conductors are the key practical materials for developing power applications at high temperatures of 77 K and high magnetic fields. The increase of number of buffer layers would result in the increase of the degree of difficulty for controlling growth, microscopy and interface structure. Therefore, simplifying architecture of buffer layers becomes important for the simplification of preparation technics and the reduction of cost for coated conductors. In this paper, we have explored the influence of thermal decomposition and preparation technics of film on the epitaxial growth of SrTiO3 (STO) buffer layers deposited on textured NiW substrates by chemical solution deposition (CSD). The results show that STO thin film with good c-axis texture and smooth surface could be obtained by choosing appropriate precursor solution and introducing seed layer before depositing the final oxide film.

The influence of oxygen partial pressure on epitaxy is systematically studied in La2Zr2O7 (LZO) thin films fabricated by metal organic deposition (MOD) on yttria stabilized zirconia (00l) single crystal substrates. The results show that oxygen partial pressure affects not only the epitaxial growth but also the morphology evolution of film. It is observed that the texture sharpness of LZO film improves while its surface flatness becomes worse with increasing oxygen partial pressure during the whole heat-treatment process. Further studies illustrate that high oxygen partial pressure at pyrolysis step favors the texture sharpening of LZO film, which is contributed to the complete decomposition of organic constitution and the decrease of residual carbon in oxide film. However, low oxygen partial pressure at crystalline step helps the improvement of surface flatness for LZO thin film. It is supposed to be linked with the decrease of oxygen vacancy defects and the increase of grain size along with the replenishment of oxygen content at the crystallization stage. Tailoring oxygen partial pressure at separate heat-treatment steps is important to improving texture sharpness and surface flatness of LZO buffer film as long as the oxidation of metallic substrate can be avoided in coated conductors.

We investigated the influence of the thermal decomposition behavior and the heat-treatment process route on the texture and morphology evolution of the LTO-gel (La3TaO7-gel) buffer layer prepared by CSD. The results show that LTO buffer layer with good c-axis texture and smooth surface could be obtained by choosing the suitable LTO precursor solution and adjusting the rapid elevated temperature processing method.

Influences of four parameters of CSD (chemical solution deposition) process to deposit LZO films on the epitaxial growth of the LZO films were studied. The results indicate that the intensity of (400) peak increases with increasing of the heating temperature, heating time and heating rate. The texture of LZO film is very sensitive to oxygen partial pressure during heat-treatment, and the oxygen partial pressure is more important than other parameters in obtaining a cube-textured LZO film. The influence of heating temperature, heating time, and heating rate could be explained by the classic nucleation and growth theory. However, oxygen partial pressure has a dual role, one is to decrease the content of residual carbon in the film, which is good for the growth of LZO grains, and the other is to weaken the inhibition of the spontaneous nucleation and growth of LZO grains due to decreasing of the content of residual carbon in the film, and finally the texture of LZO film is not a cube texture. So controlling or modifying the oxygen partial pressure at the different stages of heat-treatment may be a key to improving the kinetic of LZO grains and to not influencing the epitaxial growth of LZO film.

Texture and morphology evolution of modified Lanthanum Zirconium oxide (LaZr1.1Oy) films grown on biaxially textured Ni-5%W tapes by chemical solution deposition (CSD) method at different heat-treatment conditions has been investigated. Results show that both the growth orientation and surface morphology of films are dependent on the heating rate and annealing temperature during heat-treatment process. Compared with the annealing temperature, heating rate shows a greater influence on the orientation growth of CSD-LaZr1.1Oy film. Slow heating rate is beneficial to a single (00l) orientation growth of LaZr1.1Oy grains on textured Ni-5at.%W (Ni5W) substrate. However, the surface morphology analysis reveals a minor effect of heating rate on the grain size and surface roughness of LaZr1.1Oy film. We consider that a slow heating rate would lead to the homogeneity nucleation of LaZr1.1Oy grains and eventually forming the great textured film due to the narrow temperature interval of the complete decomposition for LaZr(1.1)Oy precursor gel. In any case, high-quality LaZr(1.1)Oy film has been achieved at annealing temperature of 900 degrees C with heating rate of 2 degrees C/min. Moreover, we have grown epitaxial CeO2 film on the textured Ni5W substrate covered by LaZr1.1Oy film using CSD approach. CeO2 precursor solution was spin-coated on short sample of Ni5W/LZO and then heat-treated at 1000 degrees C for 30 min in Ar-4%H-2. Detailed XRD and AFM studies indicate that CeO2 film has sharp bi-axial texture and smooth surface. These results demonstrate that a low-cost CSD LaZr1.1Oy film can act as a planarization template for the further production high J(c) YBCO-superconducting film. (C) 2016 Elsevier B.V. All rights reserved.

We developed a simple and stable precursor solution containing low fluorine content to fabricate YBa 2 Cu 3 O y (YBCO) films on CeO 2 /YSZ/CeO 2 buffered NiW substrates. The fluorine content in the precursor solution could be controlled at 23.1% by tuning the ratio of barium trifluoroacetate to barium acetate. Fast pyrolysis process and smooth surface of YBCO precursor films could be acquired by using the low-fluorine solution. The phase, texture, microstructure, and superconducting properties of YBCO film were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscope, and four-probe method, respectively. The crystallized YBCO film showed good out-of-plane and in-plane textures. A high critical current density J c of ~3 MA/cm 2 (77 K, 0 T) could be obtained in the YBCO/CeO 2 /YSZ/CeO 2 /NiW sample derived from the low-fluorine solution. The results indicate that the controllable fluorine content solution could be useful for epitaxial growth of YBCO films on buffered NiW substrates.

High quality YBCO precursor solution is the basis for the preparation of coated con-ductors by chemical solution deposition. In this paper, the change laws of the viscosity and re-fractive index of yttrium, barium, copper, and oxide (YBCO) precursor solutions with differ-ent concentrations and different solvents were detailed studied. The viscosity and refractive in-dex of precursor solution will increase with the increase of its concentration. The changes of properties of the solvent can also cause a significant change in the viscosity of the precursor so-lution. The viscosity of the precursor solution will increase with the increase of water content. However, the viscosity of the precursor will decrease slightly with the increase of the content of the propionic acid.

A novel room-temperature chemical synthesis technique for PbO-type FeSe superconducting nanocrystals was developed. Since no heat treatment was involved during the reaction process, the formation of non-superconducting hexagonal δ-FeSe phase has been effectively avoided and high purity of superconducting phase was guaranteed, which were proved by both X-ray diffractometer (XRD) and high-resolution transmission electron microscope (HRTEM). FeSe nanoparticles with the critical temperature, Tc of ∼ 8.9 K were obtained, which implied the effectiveness of this synthesis method. The influences of pH values on the morphology of FeSe nanoparticles and the reaction mechanisms were systematically analyzed. With the increase of pH values, the particle size decreased obviously. The reaction mechanisms with different pH values were also discussed based on the observed experimental phenomena and calculated standard electrode potentials.

In this paper, the sample of long length baseband of La2 Zr2 O7 (LZO) buffer layer with pyrochlore structure was fabricated on the NiW baseband of bi-axial texture by using of the roll to roll mode and the metal organic deposition ( MOD) technology, and X ray diffraction (XRD) and atomic force microscopy (AFM) were used to analyze the texture and surface mor-phology of the short length samples extracted from the different positions of long length baseband of buffer layer. The result indicates that the LZO film with good c axis texture and smooth sur-face is obtained. However, the texture sharpness of the long length baseband samples is less than the texture degree of the static short length sample, and we can think that in the heat treat-ment process, the walking speed of baseband that influencing the heating rate and the time of heat treatment in constant temperature is the key factor to obtain the long-length baseband buff-er layer sample with good performance.

In this paper, The La2 Zr2 O7 ( LZO) oxide thin film with pyrochlore structure was fabricated on bi-axial textured NiW substrates by chemical solution deposition ( CSD) method, and the influence of elevated temperature routes on epitaxial growth behavior of LZO films during the heat-treatment process was studied. The texture and surface morphology of LZO thin films under different heat treatments were characterized by X-ray diffraction (XRD) and a-tomic force microscopy (AFM). The result indicates that the elevated temperature rate has an important effect on the texture degree and surface morphology of LZO thin films on metallic sub-strates. It can be considered that LZO thin films with sharp texture degree and smooth surface could be obtained by choosing an appropriate heat-treatment route using CSD method. Moreo-ver, LZO thin film fabricated at the optimal heat-treatment condition is suitable to be used as the buffer layer for coated conductors.

The hierarchical carbon-coated lithium iron phosphate (LiFePO4) nano-grain microspheres are prepared by chemical co-precipitation method. The microstructure and cycling performance are compared for samples treated at 975K and 1025K. Transmission electron micrograph (TEM) analysis confirms the existence of ferric pyrophosphate phase of the general formula Fe4(P2O7)3. Reasons for the formation of the crystalline Fe4(P2O7)3 phase are intensively discussed. It is considered that a little amount of Fe4(P2O7)3 phase has no distinct detrimental effect on the cycling capacity of samples. Although there is a big decrease from 132 to 74.5mAh/g in discharge capacity at a current rate of 1C for the sample treated at 975K from 400 to 500 cycles. The capacities for the sample were observed to be recovered to its theoretical value in discharge at a current rate of 0.1C after 500 cycles. It is demonstrated that the degradation behavior for the sample treated at 975K is attributed to the increase of diffusion resistance of the lithium ions into the bulk of LiFePO4 electrode materials, which is not reported before in the literatures.

The hierarchical carbon-coated LiFePO4 nano-grain microspheres are prepared by a chemical co-precipitation method. The microstructure and electrochemical properties of LiFePO4/C composites treated at 950-1025 K are intensively investigated. The rate discharge capability has been obviously enhanced when sample is treated at 1025 K. This attributes to its improved electric conductivity of 0.09 S cm(-1) due to the in-situ formation of Fe2P phase. The cycling stabilities are excellent until 300 cycles for all the samples at the rate 1C in discharge, which is very difficult to reach for nano-grains with large specific surface area and high reaction activity. Our samples with hierarchical microstructures exhibit high Li-ion diffusion rate (10(-9)-10(-13) cm(2) S-1) with enhanced tap density (1.30 g cm(-3)). It is considered in our paper that the rate capacities increased by Li-ion diffusion rate are not as obvious as electric conductivity. Therefore, the LiFePO4/FePO4 reaction is a non-diffusional controlled process. (C) 2014 Elsevier B.V. All rights reserved.

为了制备能够满足YBCO涂层导体所需的高强、低磁性基带,采用轧制辅助双轴织构技术(RABiTS)制备Ni-5at％W(Ni5W)合金基带,在不同温度及热处理制度下进行再结晶热处理.采用背散射电子衍射技术对基带织构情况进行研究,结果表明,Ni5W合金基带的初始再结晶温度为700℃,随退火温度升高,轧制织构不断向立方织构转变,在1200℃时立方织构百分含量接近100％.采用700℃预退火30 min后在进行1200℃退火1h后,基带立方织构含量仍然很高,并且比一步退火法获得的立方织构更为锐利.

以镍粉和钨粉为起始原料,采用粉末冶金的方法形成Ni5W预合金锭,采用真空电弧炉去除杂质,实现均匀化.结合热轧、冷轧和再结晶热处理等工艺制备了厚度为80μm的Ni5W合金基带.讨论了道次加工率、总加工率对Ni5W合金基带轧制织构演变的影响.结果表明,较小的道次加工率和较大的总加工率有利于基带再结晶热处理后立方织构百分含量的提高,道次加工率对立方织构质量的影响小于总加工率.以5％的道次加工率和98％的总加工率进行冷轧后,获得了具有较高含量的S型织构和Copper型织构的基带.

Y0.9Gd0.1Ba2Cu3OY films were prepared by the chemical solution deposition method. The effect of intermediate annealing on the phase, texture and superconducting properties of the films were evaluated. The results show that the intermediate annealing process is beneficial to achieve highly c-axis oriented YGdBCO film. The YGdBCO film prepared with intermediate annealing temperature of 400 degrees C has demonstrated high performance.J(c) (77 K, self field) = 2.4 MA/cm(2).