Title of Invention	A PROCESS FOR THE PREPARATION OF NOVEL CERAMIC SUBSTRATE Ba2DyMO5.5, FOR BI-CUPRATE SUPERCONDUCTORS
Abstract	A process for the preparation of novel ceramic substrates, Ba2DyMO5.5 for Bi-cuprate superconductors by reacting salts of dysprosium, barium and Zr, Sn or Hf in an organic medium, pressing the resultant mixture in the form of pellets, calcining the pellets by heating at a temperature in the range of 1000 to 1200°C, repeating the calcinations process for 30-45 h, preferably 12h for each calcinations, at a temperature in the range of 1000-1200°C until a highly homogeneous mixture is formed, grinding the calcined material and pelletising at a pressure in the range of 3 to 4 tons/cm2, and sintering the resultant product at a temperature in the range of 1200 to 1600°C for a period of 10 to 30 h, and then cooled to room temperature by conventional method to obtain BaaDyMOs.s.

Title of Invention

A PROCESS FOR THE PREPARATION OF NOVEL CERAMIC SUBSTRATE Ba2DyMO5.5, FOR BI-CUPRATE SUPERCONDUCTORS

Abstract

A process for the preparation of novel ceramic substrates, Ba2DyMO5.5 for Bi-cuprate superconductors by reacting salts of dysprosium, barium and Zr, Sn or Hf in an organic medium, pressing the resultant mixture in the form of pellets, calcining the pellets by heating at a temperature in the range of 1000 to 1200°C, repeating the calcinations process for 30-45 h, preferably 12h for each calcinations, at a temperature in the range of 1000-1200°C until a highly homogeneous mixture is formed, grinding the calcined material and pelletising at a pressure in the range of 3 to 4 tons/cm2, and sintering the resultant product at a temperature in the range of 1200 to 1600°C for a period of 10 to 30 h, and then cooled to room temperature by conventional method to obtain BaaDyMOs.s.

Full Text	This invention relates to a process for the preparation of novel ceramic substrates, Ba2DyMO5.5 for Bi-cuprate superconductors. The immediate application of high Tc superconductors is likely to be in the form of thick and thin films in electronic devices [Alford N. McN et al., Supercond. Sci. Technol, 4 (1991) 433; pinto R. et.al. applied superconductivity (1993) 1]. In the preparation of superconducting films, substrates play a vital role and the high chemical reactivity of Bi-cuprate superconductors imposes severe restrictions on the materials available for their use as substrates for Bi-cuprate superconductors [McGinnis, W.C. et. Al. J. Mater, Res. 7 (1992) 585]. Besides for microwave applications, the substrate should have a low dielectric constant and loss factor at GHz frequencies [Preng, L.H. et. al., Supercond. Sci. Technol. 3 (1990) 233]. To the best of our knowledge, MgO is the only substrate suitable for Bi-cuparate films for microwave applications. However the Bi(Pb)SrCaCuO [BiSCCO] films developed on MgO contained mixed phases of both low Tc, Bi(2212) [TC(0)=80K] and high To, Bi(2223) [TC(0)=110K] [McGinnis, W.C. et.al., J. Mater, Res.7 (1992) 585; Agarwal, A. et. Al., Supercond. Sci Technol. 6 (1993) 670]. Other commercially available substrates such as Si, SiO2, Al2O3, SrTiO3 are either chemically reactive with BiSCCO superconductor or hrwe high dielectric constant and loss factor which makes them unsuitable or less attractive for microwave applications. Recently we have developed new substrate materials, Ba2DyMO5.5 (M=Zr, Sn and Hf) which are found to be non-reacting with BiSCCO superconductor even at extreme processing conditions and have low dielectric constant and loss factors. We have produced phase pure Bi(2223) and Bi(2223)-Ag thick films with Tc(0) =110 K and high critical current density (-104 A/cm2) on these substrates. Thus the main objective of the present invention is to develop a process for the preparation of ceramic substrates of Ba2DyMO5.5 (M=Zr, Sn and Hf) and to develop a process for the preparation of single phase Bi(2223)-Ag thick films of Tc(0) = 110 K and high critical current density on these substrates. Thus the present invention provides novel ceramic substrates, BaaDyMOs.s and a process for the preparation of superconducting Bi(2223) and Bi(2223)-Ag thick films on these new substrates. Accordingly, the present invention provides a process for the preparation of novel ceramic substrates, Ba2DyMO5.5 for Bi-cuprate superconductors where M represents at least one of the metals Zr, Sn & Hf which comprises : (i) reacting salts of dysprosium, barium and Zr, Sn or Hf in an organic medium, (ii) pressing the resultant mixture in the form of pellets, (iii) calcining the pellets by heating at a temperature in the range of 1000 to 1200°C, (iv) repeating the calcinations process for 30-45 h, preferably 12h for each calcinations, at a temperature in the range of 1000-1200°C until a highly homogeneous mixture is formed, (v) grinding the calcined material and pelletising at a pressure in the range of 3 to 4 tons/cm2, and (vi) sintering the resultant product at a temperature in the range of 1200 to 1600°C for a period of 10 to 30 h, and then cooled to room temperature by conventional method to obtain Ba2DyMO5.5. The salt of Disprosium, barium and other metals used may be selected from oxides, carbonates or nitrates. The purity of the salts may be of 99.9%. The organic medium used may be selected from organic solvents such as acetone, ethyl alcohol, isopropyl alcohol. Three multiple calcinations of the pellets may be conducted at a temperature 1000 to 1200°C for a period ranging from 10 to 15 h for each calcinations. The sintering of the final product may be effected for a period of 10 to 30 h preferably for 20 h. In view of the suitability of Ba2DyMO5.5 substrates, we have successfully screen-printed/dip-coated thick films of Bi(2223) and Bi(2223)-Ag with a zero resistivity superconducting transition at 110 K on these substrates. Thus, yet another aspect of the present invention relates to a process for the preparation of superconducting Bi(2223) and Bi(2223)-Ag thick films on new ceramic substrates of the formula Ba2DyM05.5 where M represents metals, Zr, 'Sn and Hf, useful for the preparation of superconducting films which comprises: (i) mechanically polishing the ceramic substrate of the above said formula to get highly smooth and shining surfaces, (ii) preparing thick films of Bi(2223) and Bi(2223)-Ag composites with 5-10 vol% of Ag by known methods, (iii)(a) screen printing Bi(2223) and Bi(2223)-Ag on said polished Ba2DyM05,5 substrates using a mesh size in the range of 325, or (b) dip-coating Bi(2223) and Bi(2223)-Ag on said polished Ba2DyM05 5 using a suspension of the respective powder with an organic solvent, (iv) drying the resulting films at a temperature in the range of 100 to 150°C, (v) heating the dried films at a rate of 200 to 300°C/h upto 860-880°C and soaking at this temperature for 1 to 5 minutes, (vi) cooling the film at a rate of 10°C/h to bring down the temperature to 845°C and keeping the films at this temperature for a period of 2-4 h, and (vii) cooling the film at a rate of 200°C/h upto room temperature. All the above steps are being carried out in the presence of air. The details of the invention is described in the Examples given below which are provided by way of illustration only and should not be construed to limit the scope of the invention. Example 1 Preparation of ceramic substrates of the formula Ba2DyZrO5.s Ba2DyZr05,5 was prepared by solid state reaction method. Dy203, BaCO3 and Zr02 (purity 99.9%) were taken in stoichiometric ratio, mixed thoroughly in acetone medium and calcined in air at 1150°C for 45 h with two intermediate grindings. The resultant mixture was powdered and pressed at a pressure of 5 tons/cm2, in the form of circular pellets and sintered in air at 1450° for 20 h. Example 2 Preparation of ceramic substrate of the formula Ba2DySnO5.5 Ba2DySnO5.5 was prepared by solid state reaction method. Dy203, BaCO3 and SnO2 (purity 99.9%) were taken in stoichiometric ratio, mixed thoroughly in acetone medium and calcined in air at 1100°C for 36 h with two intermediate grindings. The resultant mixture was powdered and pressed at a pressure of 4 tons/cm2 in the form of circular pellets and sintered in air at 1360°Cfor20h. Structure determination The structure of the sintered materials was examined by X-ray diffraction (XRD) method and it is found that all these materials are isostructural having a cubic perovskite structure as shown in the XRD patterns in Fig.1 (Sheet No.1) of the drawings accompanying this specification for two typical samples Ba2DyZrO5.5 (Example 1) and Ba2DySn05.5 (Example 2). In table 1a and b, we have given the computerised XRD data for these materials. Dielectric properties The dielectric properties of the substrate materials were measured in the range 30 Hz to 13 MHz frequencies and values of the dielectric constant (e1) and loss factor (tan 8) at 13 MHz frequency are 12 and 10'3 respectively at room temperature. At GHz frequencies the values of E' and tan 8 are found to be 10 and 10~5 respectively, which are ideally suitable for microwave applications. Chemical compatibility of Ba2DyMO5.5 with Bi(2223) superconductor The most important characteristics of a material to be used as a substrate for superconductors is its chemical non-reactivity with the Table 1(a): X-ray diffraction data of Ba2DyZrO5.6 (Table Removed) Table 1(b): X-ray diffraction data of Ba2DySnO5.5 (Table Removed) superconductor at the processing temperature. The chemical reactivity between Ba2DyMO5.5 and Bi(2223) was studied by mixing 1:1 vol% of Ba2DyMO5.5 and Bi(2223) and annealing the pressed pellet at 850°C for 20 h. The XRD pattern of the annealed 1:1 vol% mixture of Ba2DySnO5,5 and Bi(2223) is shown in fig.2 (Sheet No.2). The XRD pattern in the two phases in fig.2c is compared with those of pure Bi(2223) (fig.2a) and pure Ba2DySnO5.5 (fig.2b). Fig.2 shows that there is no additional phase formed, not even Bi(2212) in the annealed composite sample other than those of Bi(2223) and Ba2DySn05 5. This clearly indicates that there is no chemical reaction between Ba2DySnO5.5 and Bi(2223), even at the extreme processing conditions. Detailed percolation studies carried on Ba2DyM05,5-Bi(2223) composites confirmed that the Bi(2223) and Ba2DyM05 5 are found to remain as separate phases with their own characteristic even under severe heat treatment suggesting that Ba2DyMO5 5 can be an ideal substrate material for Bi(2223) superconductor. Ba2DyM05.5 are insulating perovskite oxides with resistivity of the order of 1010 ohm. cm. In view of the suitability of Ba2DyMO5.5 substrates, we have successfully screen-printed/dip-coated thick films of Bi(2223) and Bi(2223)-Ag with TC(0)=110 K on these new substrates. Our process for fabrication of Bi(2223) and Bi(2223)-Ag by screen-printing/dip-coating thick films on Ba2DyM05 5 substrates is given below: Before screen-printing/dip-coating Bi(2223) and Bi(2223)-Ag, Ba2DyM05,5 substrates were mechanically polished to get highly smooth and shining surfaces. For screen printing thick film paste of Bi(2223) and Bi(2223)-Ag were made by mixing respective powder with an organic vehicle. Film thickness was controlled via viscosity control of the thick film paste. This thick film paste was then screen-printed on Ba2DyMO5.5 substrates using a mesh size of 325. In the case of dip-coating the suspension of Bi(2223) and Bi(2223)-Ag were prepared by mixing their respective fine powders separately in an organic medium and the viscosities were controlled by the addition of commercially available fish oil. Thick films of Bi(2223) and Bi(2223)-Ag were prepared by dipping polished Ba2DyM05.5 substrates into respective suspension. Screen printed/dip-coated films were dried at 100° to 150°C for 2 to 3 h. Dried films were heated in a programmable furnace at a rate of 200° to 300°C/h upto 860-880°C and soaked at this temperature for 1-5 min. The films were cooled down at a rate of 10°C/h and brought down to 845°C and kept at this temperature for 2-4 h and films were then cooled down to room temperature at a rate of 200°C. All the above processes were done in air. The structure of the films were examined by X-ray diffraction method and XRD patterns of these typical thick films of Bi(2223) on Ba2DyM05 5 are shown in Fig.3 (given on sheet Nos.3,4&5). The XRD patterns of these Bi(2223) thick films showed that except for the characteristic peaks of Ba2DyM05.5 substrates, all other peaks could be assigned to a phase pure Bi(2223) superconductor. The following examples illustrate the preparation of superconducting films employing the novel substrates: Example 3 Preparation of Superconducting Bi(2223) thick film on ceramic substrate of formula Ba2DyZrO5.s Highly polished polycrystalline Ba2DyZrO5.5 substrate was used for the fabrication of Bi(2223) thick film. Thick film paste of Bi(2223) was prepared by mixing Bi(2223) with n-butanol. The viscosity of the paste was controlled by the addition of commercially available fishoil. This paste was then screen printed on Ba2DyZrO5.5 substrate using a screen of 325 mesh size. The printed film was then dried in an oven at 200°C for 3 h. The film was then heated in a programmable furnace in air at a rate of 200°C/h upto 880°C and was kept at this temperature for two minutes. It was then cooled at a rate of 10°C/h upto 845°C and kept at this temperature for 3 h and finally furnace cooled to room temperature. Example 4 Preparation of superconducting Bi(2223) thick film on ceramic substrate of formula Ba2DySnO5.s The thick film suspension of Bi(2223) for dip coating was prepared by mixing fine powder of Bi(2223) with n-butanol and the viscosity was controlled by the addition offish oil. The thick film of Bi(2223) was prepared by dipping highly polished Ba2DySnO5 5 substrate in the Bi(2223) suspension. The film is then dried in an electric oven at 150°C for 3 h. The dried film was then heated in a programmable furnace at a rate of 200°C/h upto 880°C and kept at this temperature for 3 min. The film was then cooled down upto 845°C at a rate of 10°C/h and kept at this temperature for 3 h. It was then cooled at a rate of 200°C/h to room temperature. The entire process was carried out in air. Example 5 Preparation of superconducting Bi(2223)-Ag thick film on ceramic substrate of formula Ba2DySnO5.5 Thick film suspension of Bi(2223)-Ag for dip-coating was made by mixing superconducting Bi(2223)-Ag composite powder with n-butanol. Thick film of Bi(2223)-Ag composite having 7 vol% of Ag was fabricated by dipping highly polished Ba2DySnO5.5 substrate in this suspension. The coated film was kept in an electric oven at 200°C for 3 h, to remove the organic solvent present in the film. The film was then heated in a programmable furnace in air at a rate of 300°C/h upto 870°C and kept at this temperature for 2 min and cooled at a rate of 10°C/h upto 845°C and kept at this temperature for 3 h. The film was then cooled at room temperature. The structure of the film was examined by X-ray diffraction technique. The XRD patterns of three typical thick films on Ba2DyZr05.5 (Example 3), Ba2DySn05.5 (Example 4) and Ba2DySnO5 5 (Example 5) substrates are shown in Fig.3 of the drawings (Sheet Nos.3,4 & 5) accompanying this specification. The XRD pattern of these Bi(2223) thick films showed that except for the characteristic peaks of Ba2DyM05,s substrates, all other peaks could be assigned to a phase pure Bi(2223) superconductor. Superconductivity in hese Bi(2223) thick films on Ba2DyMO5 5 substrates were studied by temperature-resistance measurements shown in fig.4 (Sheet No.6,7&8). The films show a metallic behaviour in the normal state and give zero resistivity superconducting transition at 110 K. We claim : 1. A process for the preparation of novel ceramic substrates, Ba2DyMO5.5 for Bi-cuprate superconductors where M represents at least one of the metals Zr, Sn & Hf which comprises : 1 -^o. > (i) reactingjsalts of dysprosium, barium and Zr, Sn or Hf in an organic medium, (ii) pressing the resultant mixture in the form of pellets, (iii) calcining the pellets by heating at a temperature in the range of 1000to1200°C, (iv) repeating the calcinations process for 30-45 h, preferably 12h for each calcinations, at a temperature in the range of 1000-1200°C until a highly homogeneous mixture is formed, (v) grinding the calcined material and pelletising at a pressure in the range of 3 to 4 tons/cm2, and (vi) sintering the resultant product at a temperature in the range of 1200 to 1600°C for a period of 10 to 30 h, and then cooled to room temperature by conventional method to obtain BaaDyMOs.s. 2. A process as claimed in claim 1 wherein the salts of dysprosium, barium and other metals used are selected from oxides, carbonates or nitrates. 3. A process as claimed in claims 1-2 wherein the organic medium used is acetone, alcohol. 4. A process as claimed in claims 1-3 wherein the multiple cancination of the pellets is effected for a period ranging from 30 to 45 h, preferably 12h, for each calcination. 5. A process as claimed in claims 1-4 wherein the sintering of the final product is effected for a period of 10 to 30 h, preferably for 20 h. 6. A process for the preparation of novel ceramic substrates, Ba2DyMO5.5 for Bi-cuprate superconductors substantially as herein described with reference to the examples.

Full Text

This invention relates to a process for the preparation of novel ceramic substrates, Ba2DyMO5.5 for Bi-cuprate superconductors.
The immediate application of high Tc superconductors is likely to be in the form of thick and thin films in electronic devices [Alford N. McN et al., Supercond. Sci. Technol, 4 (1991) 433; pinto R. et.al. applied superconductivity (1993) 1]. In the preparation of superconducting films, substrates play a vital role and the high chemical reactivity of Bi-cuprate superconductors imposes severe restrictions on the materials available for their use as substrates for Bi-cuprate superconductors [McGinnis, W.C. et. Al. J. Mater, Res. 7 (1992) 585]. Besides for microwave applications, the substrate should have a low dielectric constant and loss factor at GHz frequencies [Preng, L.H. et. al., Supercond. Sci. Technol. 3 (1990) 233]. To the best of our knowledge, MgO is the only substrate suitable for Bi-cuparate films for microwave applications. However the Bi(Pb)SrCaCuO [BiSCCO] films developed on MgO contained mixed phases of both low Tc, Bi(2212) [TC(0)=80K] and high To, Bi(2223) [TC(0)=110K] [McGinnis, W.C. et.al., J. Mater, Res.7 (1992) 585; Agarwal, A. et. Al., Supercond. Sci Technol. 6 (1993) 670]. Other commercially available substrates such as Si, SiO2, Al2O3, SrTiO3 are either chemically reactive with BiSCCO superconductor or hrwe high dielectric constant and loss factor which makes them unsuitable or less attractive for microwave applications.
Recently we have developed new substrate materials, Ba2DyMO5.5 (M=Zr, Sn and Hf) which are found to be non-reacting with BiSCCO superconductor even at extreme processing conditions and have low dielectric constant and loss factors. We have produced phase pure Bi(2223) and Bi(2223)-Ag thick films with Tc(0) =110 K and high critical current density (-104 A/cm2) on these substrates. Thus the main objective of the present invention is to develop a process for the preparation of ceramic substrates of Ba2DyMO5.5 (M=Zr, Sn and Hf) and to develop a process for the preparation of single phase Bi(2223)-Ag thick films of Tc(0) = 110 K and high critical current density on these substrates.
Thus the present invention provides novel ceramic substrates, BaaDyMOs.s and a process for the preparation of superconducting Bi(2223) and Bi(2223)-Ag thick films on these new substrates.
Accordingly, the present invention provides a process for the preparation of novel ceramic substrates, Ba2DyMO5.5 for Bi-cuprate superconductors where M represents at least one of the metals Zr, Sn & Hf which comprises :
(i) reacting salts of dysprosium, barium and Zr, Sn or Hf in an organic
medium,
(ii) pressing the resultant mixture in the form of pellets, (iii) calcining the pellets by heating at a temperature in the range of 1000 to 1200°C,
(iv) repeating the calcinations process for 30-45 h, preferably 12h for each calcinations, at a temperature in the range of 1000-1200°C until a highly homogeneous mixture is formed,
(v) grinding the calcined material and pelletising at a pressure in the range of 3 to 4 tons/cm2, and
(vi) sintering the resultant product at a temperature in the range of 1200 to 1600°C for a period of 10 to 30 h, and then cooled to room temperature by conventional method to obtain Ba2DyMO5.5.
The salt of Disprosium, barium and other metals used may be selected from oxides, carbonates or nitrates. The purity of the salts may be of 99.9%. The organic medium used may be selected from organic solvents such as acetone, ethyl alcohol, isopropyl alcohol. Three multiple calcinations of the pellets may be conducted at a temperature 1000 to 1200°C for a period ranging from 10 to 15 h for each calcinations. The sintering of the final product may be effected for a period of 10 to 30 h preferably for 20 h.
In view of the suitability of Ba2DyMO5.5 substrates, we have successfully screen-printed/dip-coated thick films of Bi(2223) and Bi(2223)-Ag with a zero resistivity superconducting transition at 110 K on these substrates.
Thus, yet another aspect of the present invention relates to a process for the preparation of superconducting Bi(2223) and Bi(2223)-Ag thick films on new ceramic substrates of the formula Ba2DyM05.5 where M represents
metals, Zr, 'Sn and Hf, useful for the preparation of superconducting films which comprises:
(i) mechanically polishing the ceramic substrate of the above said formula to get highly smooth and shining surfaces,
(ii) preparing thick films of Bi(2223) and Bi(2223)-Ag composites with 5-10 vol% of Ag by known methods,
(iii)(a) screen printing Bi(2223) and Bi(2223)-Ag on said polished
Ba2DyM05,5 substrates using a mesh size in the range of 325, or
(b) dip-coating Bi(2223) and Bi(2223)-Ag on said polished Ba2DyM05 5 using a suspension of the respective powder with an organic solvent,
(iv) drying the resulting films at a temperature in the range of 100 to 150°C,
(v) heating the dried films at a rate of 200 to 300°C/h upto 860-880°C and soaking at this temperature for 1 to 5 minutes,
(vi) cooling the film at a rate of 10°C/h to bring down the temperature to 845°C and keeping the films at this temperature for a period of 2-4 h, and
(vii) cooling the film at a rate of 200°C/h upto room temperature. All the above steps are being carried out in the presence of air.
The details of the invention is described in the Examples given below which are provided by way of illustration only and should not be construed to limit the scope of the invention.
Example 1
Preparation of ceramic substrates of the formula Ba2DyZrO5.s
Ba2DyZr05,5 was prepared by solid state reaction method. Dy203, BaCO3 and Zr02 (purity 99.9%) were taken in stoichiometric ratio, mixed
thoroughly in acetone medium and calcined in air at 1150°C for 45 h with two intermediate grindings. The resultant mixture was powdered and pressed at a pressure of 5 tons/cm2, in the form of circular pellets and sintered in air at 1450° for 20 h.
Example 2
Preparation of ceramic substrate of the formula Ba2DySnO5.5
Ba2DySnO5.5 was prepared by solid state reaction method. Dy203, BaCO3 and SnO2 (purity 99.9%) were taken in stoichiometric ratio, mixed
thoroughly in acetone medium and calcined in air at 1100°C for 36 h with two intermediate grindings. The resultant mixture was powdered and pressed at a pressure of 4 tons/cm2 in the form of circular pellets and sintered in air at 1360°Cfor20h.
Structure determination
The structure of the sintered materials was examined by X-ray diffraction (XRD) method and it is found that all these materials are isostructural having a cubic perovskite structure as shown in the XRD patterns in Fig.1 (Sheet No.1) of the drawings accompanying this specification for two typical samples Ba2DyZrO5.5 (Example 1) and
Ba2DySn05.5 (Example 2). In table 1a and b, we have given the computerised XRD data for these materials.
Dielectric properties
The dielectric properties of the substrate materials were measured in the range 30 Hz to 13 MHz frequencies and values of the dielectric constant (e1) and loss factor (tan 8) at 13 MHz frequency are 12 and 10'3 respectively at room temperature. At GHz frequencies the values of E' and tan 8 are found to be 10 and 10~5 respectively, which are ideally suitable for microwave applications.
Chemical compatibility of Ba2DyMO5.5 with Bi(2223) superconductor
The most important characteristics of a material to be used as a substrate for superconductors is its chemical non-reactivity with the

Table 1(a): X-ray diffraction data of Ba2DyZrO5.6
(Table Removed)
Table 1(b): X-ray diffraction data of Ba2DySnO5.5
(Table Removed)
superconductor at the processing temperature. The chemical reactivity between Ba2DyMO5.5 and Bi(2223) was studied by mixing 1:1 vol% of Ba2DyMO5.5 and Bi(2223) and annealing the pressed pellet at 850°C for 20 h. The XRD pattern of the annealed 1:1 vol% mixture of Ba2DySnO5,5 and Bi(2223) is shown in fig.2 (Sheet No.2). The XRD pattern in the two phases in fig.2c is compared with those of pure Bi(2223) (fig.2a) and pure Ba2DySnO5.5 (fig.2b). Fig.2 shows that there is no additional phase formed,
not even Bi(2212) in the annealed composite sample other than those of Bi(2223) and Ba2DySn05 5. This clearly indicates that there is no chemical
reaction between Ba2DySnO5.5 and Bi(2223), even at the extreme processing conditions. Detailed percolation studies carried on Ba2DyM05,5-Bi(2223) composites confirmed that the Bi(2223) and Ba2DyM05 5 are found
to remain as separate phases with their own characteristic even under severe heat treatment suggesting that Ba2DyMO5 5 can be an ideal substrate
material for Bi(2223) superconductor. Ba2DyM05.5 are insulating perovskite oxides with resistivity of the order of 1010 ohm. cm.
In view of the suitability of Ba2DyMO5.5 substrates, we have
successfully screen-printed/dip-coated thick films of Bi(2223) and Bi(2223)-Ag with TC(0)=110 K on these new substrates.
Our process for fabrication of Bi(2223) and Bi(2223)-Ag by screen-printing/dip-coating thick films on Ba2DyM05 5 substrates is given below:
Before screen-printing/dip-coating Bi(2223) and Bi(2223)-Ag, Ba2DyM05,5 substrates were mechanically polished to get highly smooth
and
shining surfaces. For screen printing thick film paste of Bi(2223) and Bi(2223)-Ag were made by mixing respective powder with an organic vehicle. Film thickness was controlled via viscosity control of the thick film paste. This thick film paste was then screen-printed on Ba2DyMO5.5 substrates using a
mesh size of 325. In the case of dip-coating the suspension of Bi(2223) and Bi(2223)-Ag were prepared by mixing their respective fine powders separately in an organic medium and the viscosities were controlled by the addition of commercially available fish oil. Thick films of Bi(2223) and Bi(2223)-Ag were prepared by dipping polished Ba2DyM05.5 substrates into respective suspension. Screen printed/dip-coated films were dried at 100° to 150°C for 2 to 3 h. Dried films were heated in a programmable furnace at a rate of 200° to 300°C/h upto 860-880°C and soaked at this temperature for 1-5 min. The films were cooled down at a rate of 10°C/h and brought down to 845°C and kept at this temperature for 2-4 h and films were then cooled down to room temperature at a rate of 200°C. All the above processes were done in air. The structure of the films were examined by X-ray diffraction method and XRD patterns of these typical thick films of Bi(2223) on Ba2DyM05 5 are
shown in Fig.3 (given on sheet Nos.3,4&5). The XRD patterns of these Bi(2223) thick films showed that except for the characteristic peaks of Ba2DyM05.5 substrates, all other peaks could be assigned to a phase pure
Bi(2223) superconductor.
The following examples illustrate the preparation of superconducting films employing the novel substrates:
Example 3
Preparation of Superconducting Bi(2223) thick film on ceramic substrate of formula Ba2DyZrO5.s
Highly polished polycrystalline Ba2DyZrO5.5 substrate was used for
the fabrication of Bi(2223) thick film. Thick film paste of Bi(2223) was prepared by mixing Bi(2223) with n-butanol. The viscosity of the paste was
controlled by the addition of commercially available fishoil. This paste was then screen printed on Ba2DyZrO5.5 substrate using a screen of 325 mesh
size. The printed film was then dried in an oven at 200°C for 3 h. The film was then heated in a programmable furnace in air at a rate of 200°C/h upto 880°C and was kept at this temperature for two minutes. It was then cooled at a rate of 10°C/h upto 845°C and kept at this temperature for 3 h and finally furnace cooled to room temperature.
Example 4
Preparation of superconducting Bi(2223) thick film on ceramic substrate of formula Ba2DySnO5.s
The thick film suspension of Bi(2223) for dip coating was prepared by mixing fine powder of Bi(2223) with n-butanol and the viscosity was controlled
by the addition offish oil. The thick film of Bi(2223) was prepared by dipping highly polished Ba2DySnO5 5 substrate in the Bi(2223) suspension. The film
is then dried in an electric oven at 150°C for 3 h. The dried film was then heated in a programmable furnace at a rate of 200°C/h upto 880°C and kept at this temperature for 3 min. The film was then cooled down upto 845°C at a rate of 10°C/h and kept at this temperature for 3 h. It was then cooled at a rate of 200°C/h to room temperature. The entire process was carried out in air.
Example 5
Preparation of superconducting Bi(2223)-Ag thick film on ceramic substrate of formula Ba2DySnO5.5
Thick film suspension of Bi(2223)-Ag for dip-coating was made by mixing superconducting Bi(2223)-Ag composite powder with n-butanol. Thick film of Bi(2223)-Ag composite having 7 vol% of Ag was fabricated by dipping highly polished Ba2DySnO5.5 substrate in this suspension. The coated film
was kept in an electric oven at 200°C for 3 h, to remove the organic solvent present in the film. The film was then heated in a programmable furnace in air at a rate of 300°C/h upto 870°C and kept at this temperature for 2 min and cooled at a rate of 10°C/h upto 845°C and kept at this temperature for 3 h. The film was then cooled at room temperature.
The structure of the film was examined by X-ray diffraction technique. The XRD patterns of three typical thick films on Ba2DyZr05.5 (Example 3), Ba2DySn05.5 (Example 4) and Ba2DySnO5 5 (Example 5) substrates are
shown in Fig.3 of the drawings (Sheet Nos.3,4 & 5) accompanying this specification. The XRD pattern of these Bi(2223) thick films showed that
except for the characteristic peaks of Ba2DyM05,s substrates, all other
peaks could be assigned to a phase pure Bi(2223) superconductor. Superconductivity in hese Bi(2223) thick films on Ba2DyMO5 5 substrates
were studied by temperature-resistance measurements shown in fig.4 (Sheet No.6,7&8). The films show a metallic behaviour in the normal state and give zero resistivity superconducting transition at 110 K.

We claim :
1. A process for the preparation of novel ceramic substrates, Ba2DyMO5.5 for
Bi-cuprate superconductors where M represents at least one of the metals
Zr, Sn & Hf which comprises :
1 -^o. > (i) reactingjsalts of dysprosium, barium and Zr, Sn or Hf in an organic
medium,
(ii) pressing the resultant mixture in the form of pellets, (iii) calcining the pellets by heating at a temperature in the range of
1000to1200°C, (iv) repeating the calcinations process for 30-45 h, preferably 12h for
each calcinations, at a temperature in the range of 1000-1200°C
until a highly homogeneous mixture is formed, (v) grinding the calcined material and pelletising at a pressure in the
range of 3 to 4 tons/cm2, and (vi) sintering the resultant product at a temperature in the range of
1200 to 1600°C for a period of 10 to 30 h, and then cooled to room
temperature by conventional method to obtain BaaDyMOs.s.
2. A process as claimed in claim 1 wherein the salts of dysprosium, barium and
other metals used are selected from oxides, carbonates or nitrates.
3. A process as claimed in claims 1-2 wherein the organic medium used is
acetone, alcohol.
4. A process as claimed in claims 1-3 wherein the multiple cancination of the
pellets is effected for a period ranging from 30 to 45 h, preferably 12h, for
each calcination.
5. A process as claimed in claims 1-4 wherein the sintering of the final product
is effected for a period of 10 to 30 h, preferably for 20 h.
6. A process for the preparation of novel ceramic substrates, Ba2DyMO5.5 for
Bi-cuprate superconductors substantially as herein described with reference
to the examples.

Documents:

1028-del-1996-abstract.pdf

1028-del-1996-claims.pdf

1028-del-1996-correspondence-others.pdf

1028-del-1996-correspondence-po.pdf

1028-del-1996-description (complete).pdf

1028-del-1996-drawings.pdf

1028-del-1996-form-1.pdf

1028-del-1996-form-2.pdf

1028-del-1996-form-4.pdf

1028-del-1996-petition-138.pdf

1028-del-1996-petition-others.pdf

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Patent Number

214935

Indian Patent Application Number

1028/DEL/1996

PG Journal Number

10/2008

Publication Date

07-Mar-2008

Grant Date

18-Feb-2008

Date of Filing

16-May-1996

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI- 110 001, INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	ASHA MARY JONE	SENIOR RESEARCH FELLOW,REGIONAL RESEARCH LABORATORY (CSIR), TRIVENDRUM -695019, INDIA
2	DR. ALATHUR DAMODARAN	DIRECTOR,REGIONAL RESEARCH LABORATORY (CSIR), TRIVENDRUM -695019, INDIA
3	JOSE KURIAN	SENIOR RESEARCH FELLOW,REGIONAL RESEARCH LABORATORY (CSIR), TRIVENDRUM -695019, INDIA
4	POO KODAN SAJITH	SENIOR RESEARCH FELLOW,REGIONAL RESEARCH LABORATORY (CSIR), TRIVENDRUM -695019, INDIA
5	KRISHNAN SUDERSAN KUMAR	RESEARCH SCHOLAR,REGIONAL RESEARCH LABORATORY (CSIR), TRIVENDRUM -695019, INDIA
6	RAJAN JOSE	JUNIOR FELLOW,REGIONAL RESEARCH LABORATORY (CSIR), TRIVENDRUM -695019, INDIA
7	PROF. JACOB KOSHY	SCIENTIST E-II,REGIONAL RESEARCH LABORATORY (CSIR),TRIVANDRUM-695019,INDIA

PCT International Classification Number

C04B 35/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA