METHOD FOR FABRICATION OF A HTS COATED TAPE

Abstract

A method for manufacturing an HTS coated tape (34) includes providing a substrate tape (1), depositing a textured buffer layer (3) onto a front side (7) of the substrate tape, depositing an HTS layer (32) onto the front side, and depositing a functional layer (2) onto a bottom side (6) of the substrate tape. The functional layer exerts a mechanically deforming effect on the substrate tape opposing a mechanically deforming effect on the substrate tape exerted by the textured buffer layer deposited on the front. The functional layer is at least partially deposited before and/or during the depositing of the textured buffer layer. This permits an HTS coated tape, with which higher critical currents of the HTS layer are achieved, to be produced.

Claims

1. A method for manufacturing a high temperature superconductor (HTS) coated tape, comprising providing a substrate tape, depositing a textured buffer layer onto a front side of the substrate tape, depositing an HTS layer onto the front side of the substrate tape, and depositing a functional layer onto a bottom side of the substrate tape, wherein the functional layer exerts a mechanically deforming effect on the substrate tape opposing a mechanically deforming effect on the substrate tape exerted by the textured buffer layer deposited on the front side of the substrate tape, and wherein the depositing of the functional layer is done at least partially before and/or during the depositing of the textured buffer layer.

2. A method according to claim 1, wherein at least a part of the functional layer is deposited onto the bottom side of the substrate tape before the textured buffer layer is deposited onto the front side of the substrate tape.

3. A method according to claim 1, wherein said depositing of the textured buffer layer includes a plurality of buffer layer deposition steps, and wherein said depositing of the functional layer includes a plurality of functional layer deposition steps, and wherein at least some of the buffer layer deposition steps alternate with at least some of the functional layer deposition steps.

4. A method according to claim 1, wherein said depositing of the textured buffer layer and said depositing of the functional layer comprise depositing buffer layer material on the front side concurrently with depositing functional layer material on the bottom side at a same longitudinal position of the substrate tape.

5. A method according to claim 1, wherein said depositing of the textured buffer layer comprises depositing with IBAD or ABAD or ISD.

6. A method according to claim 1, wherein said depositing of the functional layer comprises sputtering.

7. A method according to claim 1, wherein the functional layer comprises an oxide material.

8. A method according to claim 7, wherein the oxide material comprises at least one of YSZ, GdZrO and MgO.

9. A method according to claim 1, wherein the textured buffer layer and the functional layer are formed of a mutually same material.

10. A method according to claim 1, wherein the substrate tape has a width (W) of at least 3 mm and/or wherein the substrate tape has an aspect ratio A=W/T, wherein A40, with W: width of the substrate tape and T: thickness of the substrate tape.

11. A method according to claim 10, wherein the substrate tape has a width (W) of at least 12 mm, and/or wherein the substrate tape has an aspect ratio A200.

12. A method according to claim 1, further comprising: repeatedly or continuously monitoring a degree of substrate tape strain during the manufacturing of the HTS coated tape, and using the monitored degree to feedback-control said depositing of the textured buffer layer and/or said depositing of the functional layer.

13. A method according to claim 12, wherein said monitoring of the degree of substrate tape strain comprises monitoring a substrate tape curvature with respect to a width direction of the substrate tape.

14. A method according to claim 1, further comprising limiting a substrate tape curvature with respect to a width direction of the substrate tape such that a maximum mutual inclination of surface areas of the substrate tape does not exceed 4 at any time during said depositing of the textured buffer layer.

15. A method according to claim 14, wherein the substrate tape curvature with respect to the width direction of the substrate tape is limited such that the maximum mutual inclination of the surface areas of the substrate tape does not exceed 2 at any time during said depositing of the textured buffer layer.

16. A method according to claim 1, further comprising: during said depositing of the textured buffer layer and said depositing of the functional layer, translating the substrate tape between two reservoirs at least once, and during said translating between the two reservoirs, passing the substrate tape through at least one deposition zone for depositing buffer layer material and/or functional layer material on the substrate tape.

17. A method according to claim 16, wherein said depositing of the textured buffer layer and said depositing of the functional layer comprises translating the substrate tape between the two reservoirs back and forth multiple times.

18. A method according to claim 16, wherein said translating between the two reservoirs comprises: using a multipath translation area with multiple windings of the substrate tape, and twisting the substrate tape at least once by a half turn within the multipath translation area.

19. A method according to claim 1, wherein said depositing of the textured buffer layer and said depositing of the functional layer comprise cancelling out deforming effects in total, to cancel out a degree of strain in the HTS coated tape.

20. A high temperature superconductor (HTS) coated tape, comprising a substrate tape, a textured buffer layer and an HTS layer on a front side of the substrate tape, and a functional layer on a bottom side of the substrate tape, wherein mechanically deforming strain on the substrate tape of the layers on the front side and on the bottom side are in total cancelled out, such that the HTS coated tape is without strain.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0043] Embodiments for illustrating the invention are shown in the drawing.

[0044] FIG. 1 shows a schematic side view and strain status of a substrate tape being coated with functional layer material and buffer layer material during a translation process in accordance with the invention, wherein the functional layer is deposited before the textured buffer layer is deposited;

[0045] FIG. 2 shows a schematic side view and strain status of a substrate tape being coated with functional layer material and buffer layer material during a translation process in accordance with the invention, wherein the a part of the functional layer is deposited before the textured buffer layer is deposited, and a part of the functional layer is deposited after the textured buffer layer is deposited;

[0046] FIG. 3 shows a schematic side view and strain status of a substrate tape being coated with functional layer material and buffer layer material during a translation process in accordance with the invention, wherein the functional layer is deposited concurrently with the textured buffer layer at the same longitudinal position;

[0047] FIG. 4 shows a schematic side view and strain status of a substrate tape being coated with buffer layer material during a translation process according to the state of the art;

[0048] FIG. 5 shows a schematic side view and strain status of a substrate tape being coated with functional layer material and buffer layer material during a translation process in accordance with the invention, wherein deposition of functional layer material and buffer layer material is done in alternating steps;

[0049] FIG. 6A shows a schematic perspective view of a winding rack for a substrate tape being coated with buffer layer material in a first deposition zone and functional layer material in a second deposition zone, wherein in each deposition zone multiple windings of the substrate tape run in parallel, in accordance with the invention;

[0050] FIG. 6B shows a schematic side view of the winding rack of FIG. 6A;

[0051] FIG. 7A shows a schematic perspective view of a winding rack for a substrate tape being coated with buffer layer material and functional layer material in a common deposition zone, wherein the substrate type is twisted between some of the windings of the substrate tape running in parallel in the deposition zone, in accordance with the invention;

[0052] FIG. 7B shows a schematic side view of the winding rack of FIG. 7A;

[0053] FIG. 8 shows a cross-section of a HTS coated tape perpendicular to the longitudinal direction, produced in accordance with the invention.

DETAILED DESCRIPTION

[0054] It should be noted that the figures are schematic in nature, and some features may be shown in an exaggerated or understated way, in particular thicknesses of functional layer and textured buffer layer, in order to show particular features of an inventive HTS conductor tape or an inventive production method more clearly.

[0055] FIG. 1 illustrates a first variant of an inventive method for producing an HTS coated tape, when a functional layer 2 and a textured buffer layer 3 are deposited on opposing sides of a substrate tape 1 (see upper part of FIG. 1). Note that for simplicity, subsequent deposition of a HTS layer is not illustrated (but compare FIG. 8).

[0056] In the variant illustrated, the substrate tape 1 is translated in FIG. 1 from left to right, wherein the substrate tape 1 passes subsequently two deposition zones 4, 5. The substrate tape 1 is initially flat, compare state S1 (see lower part of FIG. 1 for a cross-section of the substrate tape 1 perpendicular to the longitudinal direction LD). In particular, the substrate tape 1 is not bent along its width direction WD.

[0057] At the deposition zone 4, functional layer material is deposited on one side of the substrate tape 1, called the bottom side 6. The functional layer material may be deposited by any suitable process, in particular having a sputtering nature (origin), e.g. magnetron or diode sputtering, ion beam sputtering or RF sputtering. In some cases a PLD (pulsed laser deposition) process may be employed. The functional layer 2 (or the functional layer material and the method employed for its deposition, respectively) yields a mechanically deforming effect on the substrate tape 1, causing some bending along the width direction WD, see status S2 (negative deformation), here with the side edges of the substrate tape 1 being bent downwards.

[0058] Subsequently, at deposition zone 5, buffer layer material is deposited on the other side of the substrate tape 1, called the front side 7. The buffer layer material is here deposited by an ABAD process (alternating beam assisted deposition), resulting in the textured buffer layer 3. The textured buffer layer 3 (i.e. the buffer layer material and the method for its deposition, respectively) produces a mechanically deforming effect for the substrate tape 1, too, which is opposed to the deforming effect of the functional layer 2. Accordingly, during deposition of the buffer layer material, the previous bending (negative deformation) of the substrate tape 1 is reduced until the substrate tape 1 is flat again, and further deposited buffer layer material causes an increasing bending of the substrate tape 1 (positive deformation), here with the side edges of the substrate tape 1 being bent upwards, compare status S3.

[0059] The layer thicknesses, materials and regimes for their deposition are chosen here such that the absolute values of strain of the substrate tape 1 in state S2 and in state S3 are basically identical. The strain of the substrate tape 1 with respect to the width direction WD can be expresses as a maximum mutual inclination of surface areas of a side of the substrate tape 1, here at the opposing side edges of said side of the substrate tape 1, compare the angle between the tangents laid on the side edges in the cross-section. The absolute values of the maximum mutual inclinations MI2 and MI3 in state S2 and in state S3 are about the same, i.e. |MI2|=|MI3|, and during the manufacturing process, the absolute value of the momentary maximum mutual inclination will never be above |MI2|.

[0060] When directly depositing the textured buffer layer 3 on the substrate tape 1 without using any functional layer as in the state of the art, compare FIG. 4, then the strain will increase from a flat state S1 to a final state S2, resulting in a maximum mutual inclination MI2.sub.N, wherein |MI2.sub.N| is much larger than |MI2| of FIG. 1, assuming all other conditions (in particular substrate thickness and textured buffer layer thickness) are chosen identical. This means that in the state of the art, buffer layer material deposited later on will be deposited on a substrate tape 1 with a larger bending (or strain) as compared to the inventive method as shown in FIG. 1. In turn, the buffer layer material deposited in accordance with the invention will face a reduced deformation (strain) of the substrate tape 1 during the deposition, what can improve the texture quality of the textured buffer layer 3.

[0061] The inventive variants described in the following resemble the variant of FIG. 1, so above all the differences with respect to the variant of FIG. 1 are explained.

[0062] FIG. 2 illustrates a second variant of a method for producing a HTS coated tape with respect to functional layer and textured buffer layer deposition.

[0063] In the variant of the inventive method of FIG. 2, the functional layer 2 is deposited in two steps. The initially flat substrate tape 1, compare state S1, passes through three deposition zones 4, 5, 6 here. At deposition zone 4, a first part (layer thickness part) of the functional layer 2 is deposited, causing some negative deformation, compare state S2. At deposition zone 5, the complete textured buffer layer 3 is deposited, removing the negative deformation and causing some positive deformation, see state S3. The hitherto procedure of FIG. 2 corresponds to the procedure of FIG. 1. Then a second part (layer thickness part) of the functional layer 3 is deposited, and the deforming effect of this second part of the functional layer 3 is enough to cancel out the strain of the substrate tape 1 of state S3, so that the final substrate tape 1 at state S4 is flat again. Then winding the HTS coated tape made from the substrate tape 1 coated with the textured buffer layer 3 and the functional layer 2 into a coil is facilitated, and good coil geometries allowing a high magnetic field strength may be manufactured.

[0064] FIG. 3 illustrates a third variant of a method for producing a HTS coated layer with respect to functional layer and textured buffer layer deposition.

[0065] In this variant, the deposition zone 4 for depositing functional layer material and the deposition zone 5 for depositing buffer layer material act at identical positions (or position areas, respectively) on the substrate tape 1 with respect to the longitudinal direction LD, albeit on different sides 6, 7. The functional layer 2 is grown concurrently with the textured buffer layer 3; the layer thicknesses grow in parallel without offset with the progression (translation) of the substrate tape 1 through the deposition zones 4, 5. It is thereby possible to keep balanced the deforming effects of the functional layer 2 and the textured buffer layer 3 though the entire manufacturing time. The substrate tape 1, which is initially flat as can be seen in state S1, stays flat throughout the entire manufacturing time until it reaches its final state S2. In this way, the buffer layer material is always deposited on a substrate tape 1 with no strain (bending), allowing excellent texture quality for the textured buffer layer.

[0066] In the variant of FIG. 3, a sensor 9, here an optical sensor, is used to measure the strain (here bending with respect to the width direction) of the resulting substrate tape 1 after the concurrent deposition of functional layer 2 and the textured buffer layer 2. The measurements provided via the sensor 9 are analyzed by an electronic control device 8. Depending on the measured bending, the material outputs of the respective material sources of the deposition zones 4, 5 are readjusted by the control device 8, so as to obtain a flat final substrate tape 1 as shown in state S2 (feedback control). Typically, the control device 8 is programmed to the keep the strain of the substrate tape 1 below a defined limit value. Note that a corresponding feedback control may be applied in all inventive method variants illustrated above and below, for readjusting material deposition for the manufacturing process as a whole and/or for a particular step or steps of the manufacturing process, and also repeated measurements (and controls) at different stages of the manufacturing process can be applied.

[0067] In the variant illustrated in FIG. 5, the functional layer 2 is deposited in here five steps, wherein the substrate tape 1 passes through five deposition zones 4a-4e which are arranged subsequently with respect to the progression (translation) of the substrate tape 1 in longitudinal direction LD (note that the substrate tape 1 may be deflected along its translation in longitudinal direction LD). Note that the deposition zones 4a-4e can be realized separately, or can be realized as one deposition zone which is passed through five times to realize the five deposition steps. Analogously, the textured buffer layer 3 is deposited in five steps, wherein the substrate tape 1 passes five deposition zones 5a-5e which are arranged subsequently with respect to the progression (translation) of the substrate tape 1. Again, the deposition zones 4a-4e can be realized separately, or can be realized as one deposition zone which is passed through five times to realize the five deposition steps. Further note that the deposition zones 4a-4e and 5a-5e can be realized as one deposition zone which is passed through ten times, with the substrate tape being bent as needed so as to face the material source of the deposition zone with the required side 6, 7 of the substrate (compare FIGS. 7A, 7B).

[0068] The functional layer material deposition steps and the buffer layer material deposition steps alternate. Starting from the flat substrate tape in state S1, here a first part (layer thickness part) of the functional layer is deposited at deposition zone 4a, causing a light strain (bending) in the substrate tape 1, see state S2. Then a first part (layer thickness part) of the textured buffer layer 3 is deposited, enough to remove the strain again, see the flat substrate tape 1 in state S3. Then a second part of the functional layer 2 is deposited at deposition zone 4b, causing again some strain again, see state S4, and then a second part of the textured buffer layer 3 is deposited at deposition zone 5b, removing that strain again, see state S5, and so on. The final substrate tape 1 (after deposition of the last part of the textured buffer layer 3) carrying the complete functional layer 2 and the complete textured buffer layer 3, is flat again, see state SF.

[0069] During the entire manufacturing process, the strain (deformation) of the substrate tape 1 never exceeds the strain (bending) of state S2 here, i.e. the state after deposition of only a small part (layer thickness part) of here one fifth of (here) the final functional layer 2.

[0070] Note that the process of FIG. 5 could alternatively start with a deposition of part of the textured buffer layer, and end with the deposition of a part of the functional layer, allowing for a similar limitation of the strain of the substrate tape 1 during the manufacturing process.

[0071] FIG. 6A in a perspective view and FIG. 6B in a side view show a setup for manufacturing a HTS coated tape (with respect to the deposition of the functional layer and the textured buffer layer) in a fifth variant, wherein the textured buffer layer is grown in (here) four steps, and the functional layer is grown in (here) three steps.

[0072] Substrate tape 1 is transported from a first reservoir 10 to a second reservoir 11. During this transport, the substrate tape 1 is lead over a winding rack 12, which here has four axes 13 for guide rollers 14. The substrate tape 1 is wound in a multitude of windings over the guide rollers 14.

[0073] In the variant shown, the substrate tape 1 passes through a deposition zone 5 for depositing the textured buffer layer on a front side 7 of the substrate tape 1, and through a deposition zone 4 for depositing the functional layer on a bottom side 6 of the substrate tape 1.

[0074] At the deposition zone 4, a multipath translation area 15 with three parallel windings of the substrate tape 1 is provided. Each location on the substrate tape 1, during transport of the substrate tape 1 from the reservoir 10 to the reservoir 11, will pass through the deposition area 4 three times, resulting in three deposition steps of functional layer material. At the deposition zone 5, a multipath translation area 16 with four parallel windings of the substrate tape 1 is provided. Each location on the substrate tape 1, during transport of the substrate tape 1 from the reservoir 10 to the reservoir 11, will pass through the deposition area 5 four times, resulting in four deposition steps.

[0075] Incoming substrate tape 1 passes alternatingly through the deposition zones 4 and 5 (here starting and ending with deposition zone 5), so the textured buffer layer and the functional layer are grown in alternating deposition steps offset in longitudinal direction along the substrate tape 1 (compare the similar situation in FIG. 5).

[0076] The setup shown in FIGS. 6A, 6B is well suited for depositing different materials as functional layer material and textured buffer layer material. If desired, the same materials for the functional layer and the textured buffer layer may be used, though.

[0077] FIG. 7A in a perspective view and FIG. 7B in a side view show a setup for manufacturing a HTS coated tape (with respect to the deposition of the functional layer and the textured buffer layer) in a sixth variant, wherein the textured buffer layer is grown in (here) two steps, and the functional layer is grown in (here) two steps.

[0078] Again, substrate tape 1 is transported from a first reservoir 10 to a second reservoir 11. During this transport, the substrate tape 1 is lead over a winding rack 12, which here has four axes 13 for guide rollers 14a-14d. The substrate tape 1 is wound in a multitude of windings over the guide rollers 14a-14d.

[0079] In the variant shown, the substrate tape 1 passes through a deposition zone 17 for depositing both the textured buffer layer on a front side 7 of the substrate tape 1 and for depositing the functional layer on a bottom side 6 of the substrate tape 1. At the deposition zone 17, a multipath translation area 18 with four parallel windings of the substrate tape 1 is provided between the guide rollers 14a, 14b. Each location on the substrate tape 1, during transport of the substrate tape 1 from the reservoir 10 to the reservoir 11, will pass through the deposition zone 17 four times, resulting in four deposition steps. From winding to winding in the multipath translation area 18, the substrate tape 1 is twisted by 180, here between the guide rollers 14c and 14d, compare the three twists 20. As a result, in the multipath translation area 18, the windings of the substrate tape 1 face a material source 19 of the deposition zone 17, located below the winding rack 12 here, alternatingly with the front side 7 and the bottom side 6. Accordingly, material deposition from the material source 19 will in the course of the transport of the substrate tape 1 from reservoir 10 to reservoir 11 alternatingly hit the front side 7 and the bottom side 6, resulting in respective parts (layer thickness parts) of the textured buffer layer and the functional layer on the substrate tape 1.

[0080] In this variant, the same material is used for the functional layer and the textured buffer layer.

[0081] Note that in both variants of FIGS. 6A/6B and FIGS. 7A/7B, the winding rack 12 may be passed multiple times by the substrate tape 1 if desired, by winding the substrate tape 1 back and forth between the reservoirs 10, 11, in order to increase the number of deposition steps as desired. In the variant of FIGS. 7A/7B, where both the functional layer and the textured buffer layer are deposited via the same deposition zone 17, it may be useful to have functional layer deposition steps on the (with respect to the direction of the axes 13) outer windings of the multipath translation area 18, since texture quality tends to be worse here (but this is irrelevant for strain compensation), and textured buffer layer deposition steps on the inner windings of the multipath translation area 18 where the texture quality tends to be higher (so a high critical current may be achieved). Also note that the winding rack 12 may have some other geometry, such as comprising a large drum and a small drum between which the substrate tape 1 translates.

[0082] FIG. 8 shows in a cross section perpendicular to the longitudinal direction a HTS coated tape (or HTS coated conductor) 34 in accordance with the invention, prepared using the inventive method.

[0083] On a substrate tape 1 typically made of a flexible metallic material such as stainless steel, on a front side 7, a textured buffer layer 3 is deposited, e.g. made of YSZ (yttrium stabilized zirconia). On top of the textured buffer layer 3, in the example shown, there is a cap buffer layer 31 and further a HTS (high temperature superconductor) layer 32, here made from ReBCO material (rare earth barium copper oxide, for example YBCO yttrium barium copper oxide). On top of the HTS layer 32, there is a metallic envelope (also called shunt layer or capping layer) 33 made of copper or a noble metal such as silver or gold.

[0084] On a bottom side 6 of the substrate tape 1, there is deposited a functional layer 2.

[0085] The layers deposited on the front side 7, and above all the textured buffer layer 3, exert a deforming effect on the substrate tape 1. However, the functional layer 2 on the bottom side 6 also exerts a deforming effect on the substrate tape 1, opposing the deforming effect of the layers on the front side 7 of the substrate tape 1.

[0086] By depositing the functional layer 2 at least partially before and/or at least partially during the deposition of the textured buffer layer 3, a strain (in particular bending with respect to the width direction WD) of the substrate tape 1 may be limited. The invention is particularly suited for substrate tapes 1 with a high aspect ratio A=W/T, with W: width of the substrate tape and T: thickness of the substrate tape 1 (measured in normal direction, i.e. perpendicular to the width direction WD and the longitudinal direction), such as with A40, preferably A80, and most preferably A200.

LIST OF REFERENCE SIGNS

[0087] 1 substrate tape [0088] 2 functional layer [0089] 3 textured buffer layer [0090] 4 deposition zone (functional layer) [0091] 4a-4e deposition zones (functional layer) [0092] 5 deposition zone (textured buffer layer) [0093] 5a-5e deposition zones (functional layer) [0094] 6 bottom side [0095] 7 front side [0096] 8 control unit [0097] 9 sensor [0098] 10 reservoir [0099] 11 reservoir [0100] 12 winding rack [0101] 13 axis [0102] 14, 14a-14d guide rollers [0103] 15 multipath translation area [0104] 16 multipath translation area [0105] 17 deposition zone (common for functional layer and textured buffer layer) [0106] 18 multipath translation area [0107] 19 material source [0108] 20 twist [0109] 31 cap buffer layer [0110] 32 HTS layer [0111] 33 metallic envelope [0112] 34 HTS coated tape [0113] LD longitudinal direction [0114] MI2, MI3 maximum mutual inclination at states S2, S3 [0115] MI2.sub.N maximum mutual inclination not using a functional layer at state S2 [0116] S1-S5, SF states (substrate tape) [0117] T thickness [0118] W width [0119] WD width direction