CN101333655A - Process for preparing La2Zr2O7 cushioning layer film of high-temperature superconductivity coating conductor - Google Patents

Abstract

The invention discloses a preparation process of a La2Zr2O7 buffer layer film used for a high temperature superconducting coating conductor, which uses a chemical solution method to prepare a biaxial texture La2Zr2O7 buffer layer film. A lanthanum acetylacetonate powder and a zirconium acetylacetone powder with the same molar ratio are dissolved in propionic acid, and are roasted after agitation for getting a precursor solution; and a substrate is roasted after coating or spin coating in the precursor solution, then the vacuum annealing is conducted, thereby obtaining the even and compact La2Zr2O7 buffer layer film with biaxial texture. The concentration of the precursor solution in use is appropriate at 0.4 to 0.8mol/l.

Description

Conductor of high-temperature superconductor coat La 2Zr 2O 7Buffer layer thin film preparation technology

Technical field

The present invention relates to a kind of La of conductor of high-temperature superconductor coat ₂Zr ₂O ₇Buffer layer thin film preparation technology belongs to the high-temperature superconducting thin film technical field of material.

Background technology

The technology of preparing of the cushioning layer material of conductor of high-temperature superconductor coat all is a guardian technique that is restricting the development of s-generation belt material of high temperature superconduct all the time.A lot of materials all once were used as buffer layer, early stage people attempt to adopt noble metals such as Ag, Pt, Pd as buffer layer, but join problem with multiple texture owing to there is lattice vector, they are also unsuccessful, the stable zirconium white (YSZ) of yttrium was found to be the buffer layer of RABiTS band preferably afterwards, and X.D.Wu in 1991 etc. have reported CeO ₂Be the better buffer layer of YBCO growth, it quite mates with YBCO on lattice, and is chemically highly stable with YBCO.Goyal in 1996 etc. utilize PLD with CeO ₂With YSZ as buffer layer, obtained nearly 1MA/cm first ²The coating conductor of critical current density (77K).From then on CeO ₂Be widely used in the cushioning layer material of grow oxide superconductor on various monocrystalline and the metallic matrix.Takahashi etc. once utilized CeO ₂As buffer layer the Ag of texture with on obtain the YBCO of good biaxial texture.Yet CeO ₂Individual defective is arranged, promptly when its thickness surpasses certain value (being about 50nm) it just have crackle to occur, so Ni/CeO ₂/ YSZ/YBCO just becomes standard construction, wherein a CeO of early stage coating conductor ₂Thin (＜50 μ m) and YSZ thicker (1 μ m).Because YSZ and YBCO not fine coupling on lattice increase the thin CeO of one deck thereon ₂Can effectively improve the YBCO quality.

But because multi-buffering-layer structure technical matters more complicated, the preparation difficulty is bigger, so people are seeking effective single cushioning layer material always.La for example _0.7Si _0.3MnO ₃, SrRuO ₃, LaMnO ₃, LaNiO ₃And NdGaO ₃Once attempted as single cushioning layer material Deng all, especially preceding two kinds of quilts are had an optimistic view of especially, because they conduct electricity, are expected to strengthen the electric stability of whole coating conductor.The short sample coating conductor of single buffer layer once had Jc (77K) to surpass 1MA/cm ²Report, but do not see as yet that so far important breakthrough is arranged.People will Ni base alloy/CeO now ₂/ YSZ/CeO ₂/ RE123 is considered as the standard construction of RABITS technological line, and has been successfully used to the long band preparation of Reel-to-Reel.

2000, Paranthaman etc. (ORNL) reported and have utilized the Sol-Gel method to prepare a kind of novel buffer layer La on the Ni matrix ₂Z ₂RO ₇, the biaxial texture better performances is utilized vacuum method epitaxy YSZ/CeO again ₂Behind/YBCO the layer, Jc (77K, self-fields) reaches 0.48MA/cm ²After 2 years, they bring up to 1.2MA/cm to the Jc value ²2005, IFW Dresden reported by the Sol-Gel legal system and has been equipped with double-layer bumper layer La ₂Zr ₂O ₇/ CeO ₂, FWHM can reach below 7 ° in the face.Because LZO has pyrochlore constitution, with the lattice mismatch of Ni less than 8%, with the lattice mismatch of YBCO less than 1%, have high chemical stability and thermostability simultaneously, even in the time of 1500 ℃, can not undergo phase transition.Therefore, La ₂Zr ₂O ₇More and more be subject to people's attention as a kind of very potential cushioning layer material.

Summary of the invention

The present invention is directed to present individual layer buffer layer thin film and can not play the effect of efficient buffer layer, and the technology of preparing of multilayer film is too complicated, and the cost height.By chemical solution deposition (CSD) method, be the La of feedstock production biaxial texture with methyl ethyl diketone lanthanum and methyl ethyl diketone zirconium ₂Zr ₂O ₇The buffer layer thin film technical matters.Its concrete steps are as follows:

(1) is the ratio of identical mol ratio in methyl ethyl diketone lanthanum and methyl ethyl diketone zirconium, takes by weighing an amount of methyl ethyl diketone lanthanum (La[CH respectively ₃COCHCOCH ₃] ₃XH ₂O) and methyl ethyl diketone zirconium (Zr[CH ₃COCHCOCH ₃] ₄) the organic salt powder, powder dissolution in an amount of propionic acid, is at room temperature stirred 6～10h, treat can stop to stir behind the solution homogeneous transparent; Solution put in the baking oven at 70～90 ℃ obtaining precursor aqueous solution behind baking 5～7h down;

(2) with the LaAlO of biaxial texture ₃Monocrystal chip cleans 20min in the acetone ultrasonic wave, clean and dry up with dehydrated alcohol again, during coating, make substrate in precursor aqueous solution, stop 10～20s after, withdraw from solution with 3～4cm/min again; Or the employing spin coating, the rotating speed of sol evenning machine is 800～2000 commentaries on classics/min, the spin coating time is 20～40s;

(3) substrate that will scribble precursor aqueous solution 70～100 ℃ of baking 20～30min in baking oven, put into vacuum tube furnace then, temperature rise rate before 180 ℃ is 3～5 ℃/min, stop 20～30min at 180 ℃, and temperature rise rate is 10 ℃/min after 180 ℃, be warmed up to 700～1000 ℃ of annealing 2～4h, last furnace cooling can obtain the La of biaxial texture and even compact ₂Zr ₂O ₇Buffer layer thin film.

The concentration of precursor aqueous solution is 0.4～0.8mol/L.In the above-mentioned temperature-rise period, should make substrate stop 30min, to slough the moisture that it contains at 180 ℃.Temperature rise rate is lower before 180 ℃, and about 3～5 ℃/min makes roughness of film become big to avoid violent organic reaction.Be the thin film crystallization stage afterwards, it is 10 ℃/min that its temperature rise rate is brought up to, until reaching top temperature.

The invention provides the technology of preparing of a kind of novel buffer layers of high-temperature superconducting coating conductors under non-vacuum condition.Epitaxially grown La on monocrystalline ₂Zr ₂O ₇The strong halfwidth in peak of the inside and outside texture of the face of buffer layer thin film reaches 5.7 ° and 4.8 ° respectively, and the surface keeps uniform and smooth and do not have a crackle, this its on the epitaxy superconducting layer good texture template is provided.

Description of drawings

Fig. 1. single crystal La AlO ₃On La ₂Zr ₂O ₇The X-ray diffractogram of film

Fig. 2. single crystal La AlO ₃On La ₂Zr ₂O ₇The utmost point figure of film

Fig. 3 .La ₂Zr ₂O ₇(222) φ scintigram of buffer layer thin film

Fig. 4 .La ₂Zr ₂O ₇(222) ω scintigram of buffer layer thin film

Fig. 5. single crystal La AlO ₃On La ₂Zr ₂O ₇The atomic force microscope figure of film

Embodiment

Below in conjunction with several concrete examples the present invention is set forth

Embodiment 1

Take by weighing methyl ethyl diketone lanthanum (La[CH ₃COCHCOCH ₃] ₃XH ₂O) 1.92g, methyl ethyl diketone zirconium (Zr[CH ₃COCHCOCH ₃] ₄) 1.91g, after the baking two kinds of acetylacetonates are joined in the 10ml propionic acid solution and at room temperature stir 8h, up to solution present faint yellow and homogeneous transparent till, the concentration of using the propionic acid regulator solution again is to 0.4mol/L.Solution is put into baking oven obtain precursor aqueous solution after about 7 hours in 80 ℃ of bakings.

Get the LaAlO of 1 * 1cm biaxial texture ₃Monocrystal chip cleans and dries up with dehydrated alcohol again with acetone ultrasonic cleaning 20min.Substrate is immersed in the solution behind about 15s, and the speed with about 3cm/min withdraws from solution again.Substrate 80 ℃ of baking 20min in baking oven of precursor aqueous solution will be scribbled, put into vacuum tube furnace then and be warmed up to 180 ℃ and stop 30min with 4 ℃/min, be warming up to 900 ℃ of annealing 2h with 10 ℃/min again, last furnace cooling, the inside and outside good La of texture of the face that can obtain ₂Zr ₂O ₇Buffer layer thin film.Fig. 1 has provided 2 θ scintigrams of X-ray diffraction, and as seen it presents extraordinary C axle orientation.Fig. 2 is La ₂Zr ₂O ₇(111) face utmost point figure measuring result, texture halfwidth (FWHM) was respectively 5.7 ° and 4.8 ° inside and outside the φ of Fig. 3 and Fig. 4 scanning and ω scanning result showed its face.Fig. 5 is La ₂Zr ₂O ₇The scanning electron microscope diagram sheet of film, the as seen very even and flawless appearance in its surface.

Embodiment 2

The preparation technology of embodiment 2 is substantially the same manner as Example 1, the different methods that just with coating the time, adopt spin coating.The substrate that scribbles precursor aqueous solution is placed on the glue evenning table, and the rotating speed of setting sol evenning machine is 900 commentaries on classics/min, and the time of spin coating is 25s.Pass through the annealing thermal treatment described in the example 1 again, also can obtain biaxial texture and the uniform and smooth La in surface ₂Zr ₂The O7 buffer layer thin film.

Claims (2)

1. La who is used for conductor of high-temperature superconductor coat ₂Zr ₂O ₇Buffer layer thin film preparation technology is characterized in that: with chemical solution method (CSD) preparation biaxial texture La ₂Zr ₂O ₇Buffer layer thin film, this method may further comprise the steps:

(1) is the ratio of identical mol ratio in methyl ethyl diketone lanthanum and methyl ethyl diketone zirconium, takes by weighing an amount of methyl ethyl diketone lanthanum (La[CH respectively ₃COCHCOCH ₃] ₃XH ₂O) and methyl ethyl diketone zirconium (Zr[CH ₃COCHCOCH ₃] ₄) the organic salt powder, powder dissolution in an amount of propionic acid, is at room temperature stirred 6～10h, treat can stop to stir behind the solution homogeneous transparent; Solution put in the baking oven at 70～90 ℃ obtaining precursor aqueous solution behind baking 5～7h down;

(2) with the LaAlO of biaxial texture ₃Monocrystal chip cleans 20min in the acetone ultrasonic wave, clean and dry up with dehydrated alcohol again, during coating, make substrate in precursor aqueous solution, stop 10～20s after, withdraw from solution with 3～4cm/min again; Or the employing spin coating, the rotating speed of sol evenning machine is 800～2000 commentaries on classics/min, the spin coating time is 20～40s;

(3) substrate that will scribble precursor aqueous solution 70～100 ℃ of baking 20～30min in baking oven, put into vacuum tube furnace then, temperature rise rate before 180 ℃ is 3～5 ℃/min, stop 20～30min at 180 ℃, and temperature rise rate is 10 ℃/min after 180 ℃, be warmed up to 700～1000 ℃ of annealing 2～4h, last furnace cooling can obtain the La of biaxial texture and even compact ₂Zr ₂O ₇Buffer layer thin film.

2. La according to claim 1 ₂RZr ₂O ₇Thin-film technique, the concentration that it is characterized in that precursor aqueous solution is 0.4～0.8mol/L.

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