A method for piezoelectric inkjet preparation of fluorine-doped YBCO superconducting thin films

Abstract

The application discloses a method for preparing fluorine-hybrid YBCO superconducting thin films by piezoelectric inkjet printing. By regulating the rheological properties of the precursor and constraining the printing interface thermodynamics, the problems of traditional coating formula in inkjet printing, such as stringing and splashing and uneven film formation, are solved, thereby realizing the continuous gradient preparation and mechanism screening of low-fluorine-no-fluorine hybrid YBCO system on a single substrate. The method comprises the following steps: preparing a no-fluorine precursor ink A and a fluorine-containing precursor ink B with propionic acid as a solvent, and limiting the volume concentration of ethyl cellulose to 0.1 vol% to 0.8 vol%; injecting the inks into a piezoelectric inkjet printing device, and printing a mixed precursor liquid film microzone array on a heated metal base strip by regulating the droplet ejection ratio of the ink A and the ink B in different microzones; and then sequentially performing low-temperature gradient pyrolysis and high-temperature epitaxial crystallization to obtain a YBCO superconducting thin film array with multiple microzones with different fluorine / barium molar ratios.

Description

Technical Field

[0001] This invention belongs to the field of superconducting tape technology, specifically relating to a method for preparing fluorine-hybridized YBCO superconducting thin films by piezoelectric inkjet printing. Background Technology

[0002] Rare earth barium copper oxide (REBa2Cu3O) 7-x YBCO (Reconstructed Biological Electrode) coated conductors are considered core materials driving the development of next-generation superconducting power and superconducting magnet technologies due to their excellent superconducting transition temperature and extremely high current-carrying capacity in strong magnetic fields at liquid nitrogen temperatures. Among the various REBCO superconducting thin film preparation processes, metal-organic deposition (MOD) has become one of the mainstream technologies in industry and academia due to its advantages such as not requiring vacuum equipment, easy large-area long-band continuous production, and low cost. Traditional MOD processes mainly use the trifluoroacetate (TFA-MOD) route. Although this route can prepare high-performance YBCO thin films, it releases highly toxic and corrosive hydrogen fluoride (HF) gas during heat treatment, seriously harming the environment and equipment; at the same time, the fluorine-containing precursor film undergoes severe skeleton shrinkage during pyrolysis, making it difficult to prepare thick films in one go and consuming a very long time. To solve this environmental and process bottleneck, fluorine-free metal-organic deposition technology (FF-MOD) has emerged and become a research hotspot in recent years. However, the pure fluorine-free system easily generates an extremely stable and difficult-to-decompose barium carbonate (BaCO3) mesophase during pyrolysis. Large BaCO3 particles severely disrupt the epitaxial growth of YBCO thin films, leading to random grain orientation and low superconducting critical current density. J c Significant degradation. In recent years, introducing trace amounts of fluorine-containing precursors into fluorine-free systems (i.e., the low-fluorine-free hybridization kinetic route) has proven to be an effective compromise between environmental protection and superconducting performance. Trace amounts of fluorine can preferentially induce the formation of nanoscale BaF2, serving as a flux and nucleation center for the subsequent high-temperature crystallization stage of BaCO3 decomposition. However, to find the optimal F / Ba molar hybridization ratio, the traditional trial-and-error method of "single-time solution preparation - single-time coating - single-time sintering" is extremely inefficient and cannot eliminate sintering environment errors between different batches.

[0003] High-throughput combinatorial materials science combined with piezoelectric inkjet printing technology offers a theoretical possibility for solving the aforementioned formulation screening challenges. By digitally controlling the mixing of multi-component microdroplets, dozens of formulation arrays can be generated simultaneously on an extremely small substrate area. However, directly applying traditional MOD precursor solutions to piezoelectric inkjet printing faces extremely severe hydrodynamic and thermodynamic challenges: micro-region cross-contamination caused by polymer viscoelasticity. Traditional macroscopic thick-film coating processes (such as spin coating, dip coating, or continuous slot coating) typically require the addition of high concentrations (e.g., ≥ 1.0 vol%) of polymers (such as ethyl cellulose) to maintain film thickness and prevent cracking. However, when such high-concentration, high-viscosity precursors are directly applied to piezoelectric inkjet printing with high shear rates above 1 MHz, the long polymer chains exhibit strong viscoelasticity, causing microdroplets to fail to break cleanly upon exiting the nozzle, resulting in severe "stringing" and uncontrollable satellite droplet splashing. These splashed droplets completely disrupt the boundaries of the micro-region array, leading to severe cross-contamination between samples of different concentration gradients, thus causing high-throughput screening to fail. Liquid flow and coffee ring effect at the baseband interface: When printing low-fluorine and fluorine-free inks in situ with wet-on-wet mixing on a very small area of ​​metal baseband, if the solvent evaporates too slowly, micro-regions of different concentrations will macroscopically dissolve and merge due to capillary forces; and there is generally outward capillary flow during the droplet drying process, which easily forms a "coffee ring" structure that is thin in the middle and thick at the edges, directly causing the film in the micro-region to lose its ability to epitaxially crystallize. Summary of the Invention

[0004] To address the problems in the prior art, this invention provides a method for preparing fluorinated hybrid YBCO superconducting thin films by piezoelectric inkjet printing. By controlling the rheological properties of the precursor and constraining the thermodynamics of the printing interface, the problems of stringing, splattering, and uneven film formation in traditional coating formulations during inkjet printing are solved, thereby achieving continuous gradient preparation and mechanism screening of low-fluorine to fluorine-free hybrid YBCO systems on a single substrate.

[0005] To achieve the above objectives, this invention provides a method for preparing fluorine-hybridized YBCO superconducting thin films by piezoelectric inkjet printing, comprising the following steps: (1) Ink preparation: Fluorine-free precursor ink A and fluorine-containing precursor ink B were prepared respectively; both fluorine-free precursor ink A and fluorine-containing precursor ink B used propionic acid as solvent and added ethyl cellulose as rheology modifier; the volume concentration of ethyl cellulose in fluorine-free precursor ink A and fluorine-containing precursor ink B was limited to between 0.1 vol% and 0.8 vol%; (2) Array printing: The metal substrate with an epitaxial buffer layer is fixed on the heating base plate. Using a piezoelectric inkjet printing device, by controlling the number and volume ratio of the jet droplets of the fluorine-free precursor ink A and the fluorine-containing precursor ink B in different micro-regions of the substrate, multiple discrete mixed precursor liquid film micro-region arrays with different fluorine contents are printed. (3) Heat treatment: The printed metal substrate was subjected to low-temperature gradient pyrolysis and high-temperature epitaxial crystallization in sequence to prepare a YBCO superconducting thin film array with multiple micro-regions with different fluorine / barium molar ratios.

[0006] Furthermore, the superconducting metal salt in the fluorine-free precursor ink A is a fluorine-free yttrium, barium, and copper carboxylate, which is selected from acetate or propionate.

[0007] Furthermore, the superconducting metal salt in the fluorine-containing precursor ink B is a mixed salt of fluorine-free yttrium and copper carboxylates and barium trifluoroacetate.

[0008] Furthermore, the nominal viscosity of the ethyl cellulose is 4 cP to 15 cP; the dynamic viscosity of the fluorine-free precursor ink A and the fluorine-containing precursor ink B after preparation is controlled between 2 mPa·s and 15 mPa·s at 25 °C, and the surface tension is controlled between 25 mN / m and 35 mN / m.

[0009] Furthermore, during array printing in step (2), the temperature of the heating base plate is maintained between 40 ℃ and 65 ℃, so that the droplets of the fluorine-free precursor ink A and the fluorine-containing precursor ink B in the micro-area can be dried and fixed in situ within 1 to 5 seconds after contacting the metal substrate.

[0010] Furthermore, during array printing in step (2), the mixed precursor liquid film micro-area array contains at least four independent discrete micro-areas; by adjusting the ratio of the number of jet droplets of fluorine-free precursor ink A and fluorine-containing precursor ink B in each micro-area, the total molar ratio of fluorine to barium in each micro-area of ​​the entire array is distributed in an increasing range from 0 to 2.0, and the gradient difference of the molar ratio of fluorine to barium between adjacent micro-areas is controlled between 0.1 and 0.5.

[0011] Furthermore, in step (3), the low-temperature gradient pyrolysis is carried out in a humid oxygen atmosphere, and the heating temperature is raised from room temperature to 500 ℃; wherein, within the temperature range of 300~500 ℃, the heating rate is controlled between 0.1 ℃ / min and 0.5 ℃ / min.

[0012] Furthermore, in step (3), the high-temperature epitaxial crystallization is carried out in a humid mixed atmosphere; the crystallization temperature is controlled between 750 ℃ ​​and 820 ℃, the mixed atmosphere is a nitrogen-oxygen mixture with an oxygen content of 10 ppm to 1000 ppm, and the dew point temperature of the mixed atmosphere is controlled between 15 ℃ and 30 ℃ by a water bath or humidifier.

[0013] Furthermore, the metal substrate with the epitaxial buffer layer has a Hastelloy or nickel-tungsten alloy as its base layer, and the epitaxial buffer layer comprises at least one layer of CeO2, LaMnO3, MgO and Y2O3.

[0014] Furthermore, the YBCO superconducting thin film array is located on the same metal substrate and contains at least 16 independent superconducting microregions; each superconducting microregion has the same c The micro-regions are epitaxially oriented, and the thickness of the monolayer film in each micro-region is between 100 nm and 500 nm, with each micro-region corresponding to a different F / Ba molar ratio.

[0015] Compared with existing technologies, this invention perfectly matches the hydrodynamic threshold of piezoelectric inkjet printing by defining an ultra-low concentration of rheology modifier (0.1~0.8 vol%) and a heating mechanism with a heating plate, fundamentally eliminating the viscoelastic stringing and splashing of traditional precursor liquids under micro-nozzles. Furthermore, it utilizes thermally induced reflux to suppress the "coffee ring" effect, achieving high-resolution micro-area array preparation and in-situ droplet pinning without cross-contamination. This invention utilizes digital micro-droplet control of piezoelectric nozzles to achieve in-situ hybridization of multi-component, continuous gradient low-fluorine to fluorine-free precursors on a single metal substrate in a single step. This completely eliminates the inefficient trial-and-error mode of traditional "single-time solution preparation - single-piece sintering," removes batch environmental errors, and achieves high-throughput combination screening of optimal hybridization ratios with extremely low material and time costs. The gradient hybridization process of this invention generates trace amounts of nano-BaF2 in situ within micro-regions, which significantly reduces the decomposition and activation energy of the stubborn BaCO3 phase in the fluorine-free system. Furthermore, the selected optimal hybridization ratio promotes the reconstruction of the YBCO lattice from a single weak pinning to a high-density "point-to-surface composite" defect network, greatly improving the critical current density and magnetic flux anisotropy of the superconducting thin film under complex strong magnetic fields. Attached Figure Description

[0016] Figure 1 These are the XRD patterns of YBCO in fluorine-free and low-fluorine regions prepared in Example 1 of this invention; Figure 2a These are the SEM results of the fluorine-free region YBCO prepared in Example 1 of this invention; Figure 2b These are the SEM results of the low-fluorine region YBCO prepared in Example 1 of this invention; Figure 3 This refers to the high-throughput YBCO superconducting thin film prepared in Example 1 of the present invention.J c Measurement results. Detailed Implementation

[0017] The present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0018] This invention provides a method for preparing fluorinated hybrid YBCO superconducting thin films by piezoelectric inkjet printing. It is a high-throughput combined printing scheme specifically tailored for microdroplet jetting. By maximally controlling the rheological properties of the precursor and precisely constraining the thermodynamics of the printing interface, it completely solves the problems of stringing, splattering and uneven film formation in inkjet printing of traditional coating formulations. This enables the continuous gradient preparation and mechanism screening of low-fluorine to fluorine-free hybrid YBCO systems on a single substrate. The method includes: preparing a fluorine-free precursor ink A and a fluorine-containing precursor ink B using propionic acid as a solvent, and strictly limiting the volume concentration of the rheology modifier ethyl cellulose to 0.1 vol% to 0.8 vol%, so that the dynamic viscosity of the ink is within the printable range of 2 to 15 mPa·s; injecting the above inks into a piezoelectric inkjet printer, and printing liquid film arrays containing multiple different F / Ba molar ratios on a metal substrate heated to 40 ℃ to 65 ℃ by digitally controlling the droplet ejection ratio of ink A and ink B in different micro-regions; subsequently performing heat treatment sequentially to obtain a YBCO superconducting thin film array with a continuous fluorine content gradient. This invention achieves efficient and high-throughput combination screening of low-fluorine-fluorine-free hybrid YBCO thin film formulations, significantly reducing research and development costs and time.

[0019] Specifically, the present invention will be described in detail below with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way. Unless otherwise specified, the raw materials used in the following embodiments and comparative examples are all common commercially available products that can be directly purchased in the art or prepared according to conventional methods existing in the art.

[0020] Example 1 High-throughput F / Ba gradient YBa2Cu3O was prepared using an optimal ratio of 0.4 vol% ethyl cellulose concentration. 7-x Taking the process of second-generation high-temperature superconducting tape array as an example, the specific implementation method of the process disclosed in this invention is illustrated.

[0021] First, fluorine-free precursor ink A (yttrium, barium, and copper propionates dissolved in pure propionic acid) and fluorine-containing precursor ink B (yttrium, barium, and copper trifluoroacetate dissolved in pure propionic acid) were prepared separately. Low molecular weight ethyl cellulose with a nominal viscosity of 4 cP was selected as a rheology modifier and added to ink A and ink B at a volume concentration of 0.4 vol%. The dynamic viscosity of both inks at 25 °C was measured to be approximately 6.5 mPa·s, and the surface tension was 28 mN / m. Next, Hastelloy substrates with a CeO2 buffer layer were used for array printing. The piezoelectric inkjet printer's base plate heating function was activated to maintain the substrate temperature at 50 °C. A 4x4 array (16 independent micro-regions) was designed on the baseband. The droplet ejection ratio of inks A and B in different micro-regions was controlled by a program, so that the F / Ba molar ratio of each micro-region increased stepwise from 0 to 1.5, and the gradient difference between adjacent micro-regions was controlled to be 0.1. After the mixed droplets contacted the baseband, in-situ drying and pinning were achieved within 2 seconds. Subsequently, the baseband was placed in a tube furnace for low-temperature gradient pyrolysis in a pure oxygen atmosphere, and a slow heating rate of 0.3 ℃ / min was strictly adopted within the critical temperature range of 300 ℃ to 500 ℃. Epitaxial crystallization was then carried out in a humid oxygen mixture at 800 ℃, an oxygen partial pressure of 200 ppm, and a dew point temperature of 20 ℃. The results showed that there was no stringing or splattering during the entire printing process, the boundaries of the liquid film micro-regions were clear, and there was no "coffee ring" phenomenon. Each micro-region has a film thickness of approximately 300 nm, is dense, and exhibits good epitaxy. The micro-region with an F / Ba ratio of 0.5 demonstrates the highest critical current density (4.8 MA / cm²) in this array. 2 ).

[0022] XRD and SEM analyses were performed on the YBCO superconducting thin film prepared in Example 1, see [link to relevant documentation]. Figure 1 The XRD patterns of YBCO in the fluorine-free and low-fluorine regions show that both the fluorine-free (FF-MOD) and low-fluorine (Low TFA-MOD) YBCO superconducting films exhibit strong (00l) peaks. This indicates that under optimized processes, the YBCO superconducting films prepared by fluorine-free (FF-MOD) and low-fluorine (Low TFA-MOD) methods possess good crystallinity. (See also...) Figure 2a SEM results of the fluorine-free region of YBCO show that a YBCO superconducting thin film prepared by FF-MOD can be obtained. Since no HF gas is released during the reaction process, the film surface is dense and flat. See also... Figure 2bSEM results of the low-fluorine region YBCO show that the YBCO superconducting film prepared by Low TFA-MOD exhibits numerous pores on the film surface, in addition to dense regions, due to the release of HF gas during the reaction process. Furthermore, the film surface also contains some large CuO particles. The critical current density of different regions of the high-flux YBCO superconducting film prepared in Example 1 was measured using magnetometry. Jc (See results) Figure 3 It can be seen that the F content has a certain impact on the current carrying capacity of YBCO superconducting films. In the region of extremely low F content, Jc The value even exceeded 4.8 MA / cm 2 .

[0023] Example 2 High-throughput YBa2Cu3O was prepared using the upper limit of 0.8 vol% ethyl cellulose concentration and a bottom plate heating condition of 65 °C. 7-x Taking the process of second-generation high-temperature superconducting tape array as an example, the specific implementation method of the process disclosed in this invention is illustrated.

[0024] First, using the same superconducting salts and solvents as in Example 1, ethyl cellulose with a nominal viscosity of 10 cP was added to inks A and B at a concentration of 0.8 vol% (the upper limit of concentration protected by this invention). The measured dynamic viscosity was approximately 14.5 mPa·s, which is within the upper limit of the hydrodynamic range for piezoelectric printing. Next, printing was performed on a Ni-W alloy substrate with a LaMnO3 buffer layer. The printing plate temperature was raised to 65 °C, and an array of 5 rows × 5 columns (a total of 25 independent micro-regions) was printed on the substrate. The F / Ba molar ratio was controlled to increase from 0 to 2.0, with a gradient difference of 0.08. Gradient pyrolysis was then performed. Since the polymer concentration reached the upper limit of this process, an extremely low heating rate of 0.1 °C / min was used in the range of 300 °C to 500 °C to prevent microcracks. After pyrolysis, epitaxial crystallization was performed at 780 °C. The results showed that the piezoelectric jetting process was stable, with no nozzle clogging, and the droplets dried rapidly within 1 second after contacting the 65 °C substrate. Due to the increased viscosity, the monolayer film thickness increased to approximately 450 nm. All 25 microregions of the high-throughput array successfully crystallized with smooth surfaces, and a wide range of F / Ba hybrid continuous phase diagrams were successfully obtained.

[0025] Example 3 Discrete YBa2Cu3O was prepared under limited conditions at an ultra-low ethyl cellulose concentration of 0.1 vol%. 7-x Taking the process of second-generation high-temperature superconducting tape micro-region array as an example, the specific implementation method of the process disclosed in this invention is illustrated.

[0026] First, ethyl cellulose with a nominal viscosity of 4 cP was added to the same ink system as in Example 1 at an extremely low concentration of 0.1 vol%, and the dynamic viscosity was measured to be approximately 2.5 mPa·s. Next, array printing was performed. The substrate heating temperature was set to 40 °C, and a discrete liquid film array of only 1 row × 6 columns (a total of 6 independent micro-regions) was printed on the substrate. The F / Ba molar ratios of the micro-regions were 0, 0.2, 0.4, 0.6, 0.8, and 1.0, respectively, with a gradient difference set to 0.2. Subsequently, a heat treatment process was performed. Due to the extremely low polymer content in the precursor, a relatively fast heating rate of 0.5 °C / min was used in the pyrolysis stage within the range of 300 °C to 500 °C to shorten the preparation cycle. Finally, epitaxial crystallization was performed at 820 °C. The results showed that the low-viscosity droplets spread very well on the substrate, and evaporation pinning was completed in approximately 4 seconds on a substrate at 40 °C. The final sintered film is relatively thin (approximately 150 nm), and each microregion is completely independent and immiscible, demonstrating that the combined screening method of this invention is equally applicable to the lower limit of the concentration process and small-scale arrays.

[0027] Comparative Example 1 Taking the process of attempting to print a high-throughput array using inkjet printing with a concentration of 1.2 vol% ethyl cellulose in the prior art as an example, this paper illustrates the necessity of limiting the specific range of rheological parameters and the unexpected technical effects of the present invention.

[0028] First, the same metal salt, solvent, and ethyl cellulose with a nominal viscosity of 4 cP were used as in Example 1. However, the concentration of ethyl cellulose was increased to 1.2 vol% (this concentration exceeds the protection scope of this invention and falls directly into the concentration range of conventional large-area coating processes). At this point, the dynamic viscosity of the ink was measured to soar to 28 mPa·s. Next, using the same printing equipment and substrate heating conditions as in Example 1, an attempt was made to print a 4-row × 4-column concentration gradient array on the substrate. The results showed that, due to the ethyl cellulose concentration ≥ 1.0 vol%, the ink rheological properties exceeded the tolerable operating range of the microscale piezoelectric nozzle; when a high-frequency piezoelectric driving waveform was applied, the long polymer chains exhibited extremely strong "viscoelasticity." The ink could not cleanly break into independent droplets upon leaving the nozzle, but instead stretched into ligation formations hundreds of micrometers long, which then broke uncontrollably into a large number of satellite splash droplets. These splash droplets severely contaminated adjacent micro-regions with different fluorine concentrations on the substrate, causing chaotic cross-dissolution of the preset F / Ba gradient. Ultimately, the inability to obtain discrete microregions with clear boundaries and known concentration gradients led to the complete failure of the high-throughput combinatorial screening experiment.

[0029] Examples 1, 2, and 3 are beneficial for studying the effect of rheology modifier (ethyl cellulose) concentration variations in the range of 0.1 vol% to 0.8 vol% on the hydrodynamic properties (viscosity and viscosity) of microdroplets. Z The influence of the number of micro-regions, the micro-area spreading morphology, and the final thickness of the single-layer superconducting film.

[0030] The comparison of the base plate heating conditions from 40 ℃ to 65 ℃ in Examples 1, 2 and 3 is helpful for studying the thermodynamic mechanism of evaporation pinning during the in-situ mutual dissolution of droplets in "wet-to-wet" contact, as well as the key role of the Marangoni reflux effect in suppressing "coffee rings" and ensuring the clarity of the high-resolution array boundary.

[0031] Based on the high-throughput gradient microregions within a single array in Example 1 or Example 2, the effects of different F / Ba molar hybridization ratios on the evolution dynamics of the pyrolysis intermediate competing phases (BaF2 and BaCO3), as well as the regulation of the internal defect reconstruction (point-surface composite pinning) and critical current density of the final superconducting thin film, can be systematically studied.

[0032] Based on the strong comparison between Examples 1-3 and Comparative Example 1, the critical threshold of polymer rheology for piezoelectric inkjet printing in the YBCO superconducting precursor liquid system can be clearly defined. This fully demonstrates that the polymer concentration (≥1.0 vol%) in the existing macroscopic coating process will cause fatal viscoelastic filamentation and array cross-contamination, thus highlighting the absolute necessity and unexpected technical effects of limiting specific concentration parameters in this invention.

[0033] Example 4 The method includes: (1) Ink preparation: Fluorine-free precursor ink A (yttrium, barium, and copper propionates dissolved in pure propionic acid) and fluorine-containing precursor ink B (yttrium, barium, and copper trifluoroacetate dissolved in pure propionic acid) are prepared respectively, and ethyl cellulose with a nominal viscosity specification of 15 cP is added as a rheology modifier in both inks; the volume concentration of ethyl cellulose in ink A and ink B is limited to 0.2 vol%; (2) Array printing: A metal substrate with an epitaxial buffer layer is fixed on a heating base plate. The metal bottom layer of the metal substrate is a nickel-tungsten alloy, and the epitaxial buffer layer contains an MgO layer. A piezoelectric inkjet printing device is used to control ink A and ink B. The number and volume ratio of water B jet droplets in different micro-regions of the baseband are used to print multiple discrete micro-region arrays of mixed precursor liquid film with different fluorine contents. The mixed precursor liquid film micro-region array contains 10 independent discrete micro-regions in 2 rows × 5 columns. By adjusting the ratio of the number of jet droplets of fluorine-free precursor ink A and fluorine-containing precursor ink B in each micro-region, the total molar ratio of fluorine to barium in each micro-region of the entire array is made to increase in the range of 0 to 2.0, and the gradient difference of the molar ratio of fluorine to barium between adjacent micro-regions is controlled between 0.1 and 0.5. The temperature of the heating plate is maintained at 45°C. ℃, so that the droplets of ink A and ink B in the micro-region can be dried and fixed in situ within 1 to 5 seconds after contacting the metal substrate; (3) Heat treatment: the printed metal substrate is subjected to low-temperature gradient pyrolysis and high-temperature epitaxial crystallization in sequence. The low-temperature gradient pyrolysis is carried out in a humid oxygen atmosphere, and the heating temperature is raised from room temperature to 500 ℃; in the temperature range of 300~500 ℃, the heating rate is controlled at 0.2 ℃ / min. The high-temperature epitaxial crystallization is carried out in a humid mixed atmosphere, and the crystallization temperature is controlled at 750 ℃. The mixed atmosphere is a nitrogen-oxygen mixture with an oxygen content of 10 ppm. The dew point temperature of the mixed atmosphere is controlled at 15℃ by a water bath or humidifier. YBCO superconducting thin film array with multiple micro-regions with different fluorine / barium molar ratios is prepared.

[0034] Example 5 The method includes: (1) Ink preparation: Fluorine-free precursor ink A (yttrium, barium, and copper propionates dissolved in pure propionic acid) and fluorine-containing precursor ink B (yttrium, barium, and copper trifluoroacetate dissolved in pure propionic acid) are prepared separately, and ethyl cellulose with a nominal viscosity specification of 6 cP is added as a rheology modifier in both inks; the volume concentration of ethyl cellulose in fluorine-free precursor ink A and fluorine-containing precursor ink B is limited to 0.6%. vol% %. (2) Array printing: The metal substrate with an epitaxial buffer layer is fixed on the heating base plate. The metal bottom layer of the metal substrate is Hastelloy, and the epitaxial buffer layer contains a Y2O3 layer. Using a piezoelectric inkjet printer, by controlling the number and volume ratio of the jet droplets of ink A and ink B in different micro-regions of the substrate, multiple discrete mixed precursor liquid film micro-region arrays with different fluorine contents are printed. The mixed precursor liquid film micro-region array contains 8 independent discrete micro-regions in 1 row × 8 columns. By adjusting the ratio of the number of jet droplets of fluorine-free precursor ink A and fluorine-containing precursor ink B in each micro-region, the total molar ratio of fluorine to barium in each micro-region of the entire array is increased in the range of 0 to 2.0, and the gradient difference of the molar ratio of fluorine to barium between adjacent micro-regions is controlled between 0.1 and 0.5. The temperature of the heating base plate is maintained at 55°C. ℃, so that the droplets of ink A and ink B in the micro-region can be dried and fixed in situ within 1 to 5 seconds after contacting the metal substrate; (3) Heat treatment: the printed metal substrate is subjected to low-temperature gradient pyrolysis and high-temperature epitaxial crystallization in sequence. The low-temperature gradient pyrolysis is carried out in a humid oxygen atmosphere, and the heating temperature is raised from room temperature to 500 ℃; in the temperature range of 300~500 ℃, the heating rate is controlled at 0.4 ℃ / min, and the high-temperature epitaxial crystallization is carried out in a humid mixed atmosphere; the crystallization temperature is controlled between 760 ℃, the mixed atmosphere is a nitrogen-oxygen mixture with an oxygen content of 500 ppm, and the dew point temperature of the mixed atmosphere is controlled at 25 ℃ by water bath or humidifier, so as to prepare a YBCO superconducting thin film array with multiple micro-regions with different fluorine / barium molar ratios.

[0035] Example 6 The method includes: (1) Ink preparation: Fluorine-free precursor ink A (yttrium, barium, and copper propionates dissolved in pure propionic acid) and fluorine-containing precursor ink B (yttrium, barium, and copper trifluoroacetate dissolved in pure propionic acid) are prepared separately, and ethyl cellulose with a nominal viscosity specification of 12 cP is added as a rheology modifier in both inks; the volume concentration of ethyl cellulose in both fluorine-free precursor ink A and fluorine-containing precursor ink B is limited to 0.7%. vol%; (2) Array printing: The metal substrate with an epitaxial buffer layer is fixed on the heating base plate. The metal bottom layer of the metal substrate is a nickel-tungsten alloy, and the epitaxial buffer layer contains MgO and Y2O3 layers. Using a piezoelectric inkjet printer, by controlling the number and volume ratio of the jet droplets of ink A and ink B in different micro-regions of the substrate, multiple discrete mixed precursor liquid film micro-region arrays with different fluorine contents are printed. The mixed precursor liquid film micro-region array contains 12 independent discrete micro-regions in 3 rows × 4 columns. By adjusting the ratio of the number of jet droplets of fluorine-free precursor ink A and fluorine-containing precursor ink B in each micro-region, the total molar ratio of fluorine to barium in each micro-region of the entire array is increased in the range of 0 to 2.0, and the gradient difference of the molar ratio of fluorine to barium between adjacent micro-regions is controlled between 0.1 and 0.5. The temperature of the heating base plate is maintained at 60°C. ℃; (3) Heat treatment: The printed metal substrate was subjected to low-temperature gradient pyrolysis and high-temperature epitaxial crystallization in sequence. The low-temperature gradient pyrolysis was carried out in a humid oxygen atmosphere, and the heating temperature was raised from room temperature to 500 ℃. In the temperature range of 300~500 ℃, the heating rate was controlled at 0.25 ℃ / min. The high-temperature epitaxial crystallization was carried out in a humid mixed atmosphere, and the crystallization temperature was controlled at 810 ℃. The mixed atmosphere was a nitrogen-oxygen mixture with an oxygen content of 1000 ppm. The dew point temperature of the mixed atmosphere was controlled at 30 ℃ by a water bath or humidifier. YBCO superconducting thin film array with multiple microregions with different fluorine / barium molar ratios was prepared.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of piezoelectric inkjet deposition of fluorine-doped YBCO superconducting thin films, characterized in that, Includes the following steps: (1) Ink preparation: Fluorine-free precursor ink A and fluorine-containing precursor ink B were prepared respectively; both fluorine-free precursor ink A and fluorine-containing precursor ink B used propionic acid as solvent and added ethyl cellulose as rheology modifier; the volume concentration of ethyl cellulose in fluorine-free precursor ink A and fluorine-containing precursor ink B was limited to between 0.1 vol% and 0.8 vol%; (2) Array printing: The metal substrate with an epitaxial buffer layer is fixed on the heating base plate. Using a piezoelectric inkjet printing device, by controlling the number and volume ratio of the jet droplets of the fluorine-free precursor ink A and the fluorine-containing precursor ink B in different micro-regions of the substrate, multiple discrete mixed precursor liquid film micro-region arrays with different fluorine contents are printed. (3) Heat treatment: The printed metal substrate was subjected to low-temperature gradient pyrolysis and high-temperature epitaxial crystallization in sequence to prepare a YBCO superconducting thin film array with multiple micro-regions with different fluorine / barium molar ratios.

2. The method for preparing fluorine-hybridized YBCO superconducting thin films by piezoelectric inkjet printing according to claim 1, characterized in that, The superconducting metal salt in the fluorine-free precursor ink A is a fluorine-free yttrium, barium, and copper carboxylate, which is selected from acetate or propionate.

3. The method of claim 1, wherein the piezoelectric inkjet method is used to fabricate a fluorine-doped YBCO superconducting thin film. The superconducting metal salt in the fluorine-containing precursor ink B is a mixed salt of fluorine-free yttrium and copper carboxylates and barium trifluoroacetate.

4. The method of claim 1 or 2 or 3 for the piezoelectric inkjet fabrication of fluorine-doped YBCO superconducting thin films, characterized in that, The nominal viscosity of the ethyl cellulose is 4 cP to 15 cP; the dynamic viscosity of the fluorine-free precursor ink A and the fluorine-containing precursor ink B after preparation is controlled between 2 mPa·s and 15 mPa·s at 25 °C, and the surface tension is controlled between 25 mN / m and 35 mN / m.

5. The method of claim 1, wherein the piezoelectric inkjet method is used to fabricate a fluorine-doped YBCO superconducting thin film. During array printing in step (2), the temperature of the heating base plate is maintained between 40 ℃ and 65 ℃, so that the droplets of fluorine-free precursor ink A and fluorine-containing precursor ink B in the micro-area can be dried and fixed in situ within 1 to 5 seconds after contacting the metal substrate.

6. The method of claim 1 or 5, wherein the piezoelectric inkjet method is used to fabricate a fluorine-doped YBCO superconducting thin film. When performing array printing in step (2), the mixed precursor liquid film micro-area array contains at least 4 independent discrete micro-areas; by adjusting the ratio of the number of jet droplets of fluorine-free precursor ink A and fluorine-containing precursor ink B in each micro-area, the total molar ratio of fluorine to barium in each micro-area of ​​the entire array is distributed in an increasing range from 0 to 2.0, and the gradient difference of the molar ratio of fluorine to barium between adjacent micro-areas is controlled between 0.1 and 0.

5.

7. The method for preparing fluorine-hybridized YBCO superconducting thin films by piezoelectric inkjet printing according to claim 1, characterized in that, In step (3), the low-temperature gradient pyrolysis is carried out in a humid oxygen atmosphere, and the heating temperature is raised from room temperature to 500 ℃; wherein, in the temperature range of 300~500 ℃, the heating rate is controlled between 0.1 ℃ / min and 0.5 ℃ / min.

8. The method of claim 1 or 7, wherein the piezoelectric inkjet method is used to fabricate a fluorine-doped YBCO superconducting thin film. In step (3), the high-temperature epitaxial crystallization is carried out in a humid mixed atmosphere; the crystallization temperature is controlled between 750 ℃ ​​and 820 ℃, the mixed atmosphere is a nitrogen-oxygen mixture with an oxygen content of 10 ppm to 1000 ppm, and the dew point temperature of the mixed atmosphere is controlled between 15 ℃ and 30 ℃ by a water bath or humidifier.

9. The method of claim 1, wherein the piezoelectric inkjet method is used to fabricate a fluorine-doped YBCO superconducting thin film. The metal base layer of the metal-based tape with an epitaxial buffer layer is Hastelloy or nickel tungsten alloy, and the epitaxial buffer layer comprises at least one layer of CeO2, LaMnO3, MgO and Y2O3.

10. The method for preparing fluorine-hybridized YBCO superconducting thin films by piezoelectric inkjet printing according to claim 1, characterized in that, The YBCO superconducting thin film array is located on the same metal substrate and contains at least 16 independent superconducting microregions; each superconducting microregion has the same c The micro-regions are epitaxially oriented, and the thickness of the monolayer film in each micro-region is between 100 nm and 500 nm, with each micro-region corresponding to a different F / Ba molar ratio.

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