- Email: [email protected]
Preparation of BaHfO3 using a spray drying method
Materials Letters 15 (1993) North-Holland
Preparation
331-333
of BaHfO, using a spray drying method
J.L. Zhang and J.E. Evetts Departmmr
Received
qf Mater&
22 October
Science and .Wetallurg):
University
@“Cambridge,
P~wzhroke Wee!.
Cambridge
CR2 3Q.Z. 1JK
1992
Homogeneous powder of BaHfO, has been synthesised by the spray drying technique using HfOCi2~8H20and BaCO, as starting materials. The interaction bet,ween YBa&u30,_, (YBCO) and BaHR& was studied by X-ray diffraction after high-temperature heat treatment. The results suggest that BaHfO, is a promising material for YBCO film deposition and as a container material for bulk YBCO.
Since the discovery of high-temperature superconductor YBa2Cu307_-r (YBCO), many efforts have been made to obtain suitable substrate materials for thin film deposition and container materials for bulk materials and crystal growth. The basic requirement for these materials is that there should be negligible reaction between the superconductor and the material for the temperatures and reaction times of interest. Among the substrate materials previously investigated are non-metals such as Si, .41,05. SrTiO,, ZrOz and MgO, and metals such as Ag, Cu and Nb [ l-41. However, most of them react with YBCO. Some studies on the YBCO/Zr02 interface have shown that no further reaction occurs after a secondary phase BaZr03 is formed, which indicates that BaZrOs is a stable material with YBCO [ I ,2 1. Since hafnium and zirconium are quite similar with regard to their structure and chemical properties, we have studied the interaction between BaHfO, and YBCO to explore the possibility of using BaHfO, as a new material compatible with YBCO. In addition, in ordcr to solve problems associated with the solid state reaction method {high sintering temperature and less tlonlogeneous powder). the spray drying technique was used to prepare BaHfO,. In this paper, the method of synthesis of BaHf03 by spray drying is presented. and the interaction between YBCO and BaHfO, is investigated. Spray drying is the process by which a fluid fed material is transformed into a dry powder by spraying the feed into a hot drying medium. the method 0167-577x/93/$
06.00 8 1993 Elsevier Science Publishers
can produce a powder of uniform and reproducible character [5,6]. Since Hf is quite stable and hafnium nitrate is not available, hafnium oxychloride was used instead. The solution for spray drying was prepared by dissolving HfOC12.8Hz0 and BaC03 in distilled water by adding HCl to obtain a Ba:Hf atom ratio of 1 : 1. The spray drying process consisted of atomising the solution in a container of swirling hot air, followed by a drying step using a Buchi 190 spray dryer. The inlet and outlet temperatures were controlled at about 230 and 14O’C respectively. Differential thermal analysis, thermogravimetric analysis and X-ray diffraction analysis were carried out to determine a suitable calcination temperature. The results indicate that a temperature above 1 tOOcC is required to get rid of the chloride ion. The powders yielded by spray drying, were then calcined at 1150°C for about 20 h and the resulting powders were characterised by X-ray diffraction using Cu Ka radiation. YBCO powder was also made by the spray drying method from an aqueous solution of yttrium nitrate, barium nitrate and copper nitrate with a Y: Ba: Cu atom ratio of I : 2 : 3. The powder. from spray drying, was then calcined at about 800°C for 5 to 10 h. Fig. 1 shows the XRD pattern of BaHf03 from spray drying. As can be seen from the figure, a single phase of BaHfO, has been obtained and indexed. To study the possible reaction between YBCO and BaHfO,, YBCO-BaHfOll composite was made by mixing YBCO and BaHf03 powders with a nominal composition of 50 ~01% YBCO and 50 vol% BaHfOj.
B.V. 411 rights reserved.
331
Volume 15, number
MATERIALS
$6
January
LETTERS
I993
5000
4000
3000
2000
1000
0.0
Fig.
1.X-ray diffraction
pattern
for BaHfO,
from spray drying.
4000
lcountsl
II
'I:
YBC
3500 (HKL)
:
eatif 03
3000
2500
2000
15oc
1ooc
5oc
Fig. 2. X-ray diff~ction
pattern
The composites were formed to maximise the interfacial area between the reactants, and thus to speed up the possible reaction at a given temperature. The composites were then pressed and put into a furnace and sintered at 1000°C for 10 h. The samples were 332
for BaHfO,+YBCO
studied If there YBCO Fig. BaHfO,
at 1000°C for 10 h.
by XRD to investigate the possible reaction. had been a reaction, a third phase besides and BaHfD, could have been expected. 2 shows the XRD pattern of the YBCOcomposite after heat treatment. All the dif-
Volume
15,number 5,6
MATERIALS
fraction peaks can be indexed according to the peaks expected for YBCO and BaHfO+ So the YBCOBaHfO, composite sample shows no phase composition change even after heat treatment at 1000°C for 10 h, and there is no detectable reaction between them at this temperature. Also, because no signiticant degradation occurred under the most stringent conditions for chemical reaction, we believe that the solubility of yttrium and copper in BaHfO, is minimal. Since the temperature used for the deposition of YBCO films is usually below 900°C BaHfO, will be a stable substrate material for the deposition of YBCO films. In comparison, a YBCO-BaZr03 composite was also made and underwent similar heat treatment at 950°C for 5 h and 1000°C for 10 h, respectively. Xray diffraction analysis shows virtually no change between the XRD pattern at 95O’C for 5 h and that of the YBCO-BaZrO, composite without heat treatment. However. the diffraction peaks of YBCO decreased considerably after treatment at 1000°C for
LETTERS
January
1993
10 h, indicating that partial reaction occurred in the composite sample. In summary, homogeneous BaHfO, powder has been prepared by the spray drying method. The present investigation of the interaction between YBCO and BaHfO, suggests that BaHf03 is an inert material for YBCO and a potential substrate material for the deposition of YBCO films. Also, it is a promising material for use as a container for processing bulk material, and as a crucible material for crystal growth. In addition, BaHfO, seems to be a more stable material than BaZrO,.
References [ 1] C.T. Cheung and E. Ruckenstein,
J. Mater. Res. 4 (1989)
I.
[ 21 L.A. Tietz and C.B. Carter, J. Mater. Res. 4 ( 1989) 1072. [3] B.R. Powell and R.L. Bloink. J. Mater. Sci. 26 ( 1991) 6507. [ 41 S. Kikkawa and F. Kanama~, J. Mater. Sci. Letters 1I (1992) 9. [ 51S.J. Lukasiewicz, J. Am. Ceram. Sot. 72 ( 1989) 617. [6] K. Masters, Spray drying, 4th Ed. (Wiley, New York, 1985).
333
Preparation
331-333
of BaHfO, using a spray drying method
J.L. Zhang and J.E. Evetts Departmmr
Received
qf Mater&
22 October
Science and .Wetallurg):
University
@“Cambridge,
P~wzhroke Wee!.
Cambridge
CR2 3Q.Z. 1JK
1992
Homogeneous powder of BaHfO, has been synthesised by the spray drying technique using HfOCi2~8H20and BaCO, as starting materials. The interaction bet,ween YBa&u30,_, (YBCO) and BaHR& was studied by X-ray diffraction after high-temperature heat treatment. The results suggest that BaHfO, is a promising material for YBCO film deposition and as a container material for bulk YBCO.
Since the discovery of high-temperature superconductor YBa2Cu307_-r (YBCO), many efforts have been made to obtain suitable substrate materials for thin film deposition and container materials for bulk materials and crystal growth. The basic requirement for these materials is that there should be negligible reaction between the superconductor and the material for the temperatures and reaction times of interest. Among the substrate materials previously investigated are non-metals such as Si, .41,05. SrTiO,, ZrOz and MgO, and metals such as Ag, Cu and Nb [ l-41. However, most of them react with YBCO. Some studies on the YBCO/Zr02 interface have shown that no further reaction occurs after a secondary phase BaZr03 is formed, which indicates that BaZrOs is a stable material with YBCO [ I ,2 1. Since hafnium and zirconium are quite similar with regard to their structure and chemical properties, we have studied the interaction between BaHfO, and YBCO to explore the possibility of using BaHfO, as a new material compatible with YBCO. In addition, in ordcr to solve problems associated with the solid state reaction method {high sintering temperature and less tlonlogeneous powder). the spray drying technique was used to prepare BaHfO,. In this paper, the method of synthesis of BaHf03 by spray drying is presented. and the interaction between YBCO and BaHfO, is investigated. Spray drying is the process by which a fluid fed material is transformed into a dry powder by spraying the feed into a hot drying medium. the method 0167-577x/93/$
06.00 8 1993 Elsevier Science Publishers
can produce a powder of uniform and reproducible character [5,6]. Since Hf is quite stable and hafnium nitrate is not available, hafnium oxychloride was used instead. The solution for spray drying was prepared by dissolving HfOC12.8Hz0 and BaC03 in distilled water by adding HCl to obtain a Ba:Hf atom ratio of 1 : 1. The spray drying process consisted of atomising the solution in a container of swirling hot air, followed by a drying step using a Buchi 190 spray dryer. The inlet and outlet temperatures were controlled at about 230 and 14O’C respectively. Differential thermal analysis, thermogravimetric analysis and X-ray diffraction analysis were carried out to determine a suitable calcination temperature. The results indicate that a temperature above 1 tOOcC is required to get rid of the chloride ion. The powders yielded by spray drying, were then calcined at 1150°C for about 20 h and the resulting powders were characterised by X-ray diffraction using Cu Ka radiation. YBCO powder was also made by the spray drying method from an aqueous solution of yttrium nitrate, barium nitrate and copper nitrate with a Y: Ba: Cu atom ratio of I : 2 : 3. The powder. from spray drying, was then calcined at about 800°C for 5 to 10 h. Fig. 1 shows the XRD pattern of BaHf03 from spray drying. As can be seen from the figure, a single phase of BaHfO, has been obtained and indexed. To study the possible reaction between YBCO and BaHfO,, YBCO-BaHfOll composite was made by mixing YBCO and BaHf03 powders with a nominal composition of 50 ~01% YBCO and 50 vol% BaHfOj.
B.V. 411 rights reserved.
331
Volume 15, number
MATERIALS
$6
January
LETTERS
I993
5000
4000
3000
2000
1000
0.0
Fig.
1.X-ray diffraction
pattern
for BaHfO,
from spray drying.
4000
lcountsl
II
'I:
YBC
3500 (HKL)
:
eatif 03
3000
2500
2000
15oc
1ooc
5oc
Fig. 2. X-ray diff~ction
pattern
The composites were formed to maximise the interfacial area between the reactants, and thus to speed up the possible reaction at a given temperature. The composites were then pressed and put into a furnace and sintered at 1000°C for 10 h. The samples were 332
for BaHfO,+YBCO
studied If there YBCO Fig. BaHfO,
at 1000°C for 10 h.
by XRD to investigate the possible reaction. had been a reaction, a third phase besides and BaHfD, could have been expected. 2 shows the XRD pattern of the YBCOcomposite after heat treatment. All the dif-
Volume
15,number 5,6
MATERIALS
fraction peaks can be indexed according to the peaks expected for YBCO and BaHfO+ So the YBCOBaHfO, composite sample shows no phase composition change even after heat treatment at 1000°C for 10 h, and there is no detectable reaction between them at this temperature. Also, because no signiticant degradation occurred under the most stringent conditions for chemical reaction, we believe that the solubility of yttrium and copper in BaHfO, is minimal. Since the temperature used for the deposition of YBCO films is usually below 900°C BaHfO, will be a stable substrate material for the deposition of YBCO films. In comparison, a YBCO-BaZr03 composite was also made and underwent similar heat treatment at 950°C for 5 h and 1000°C for 10 h, respectively. Xray diffraction analysis shows virtually no change between the XRD pattern at 95O’C for 5 h and that of the YBCO-BaZrO, composite without heat treatment. However. the diffraction peaks of YBCO decreased considerably after treatment at 1000°C for
LETTERS
January
1993
10 h, indicating that partial reaction occurred in the composite sample. In summary, homogeneous BaHfO, powder has been prepared by the spray drying method. The present investigation of the interaction between YBCO and BaHfO, suggests that BaHf03 is an inert material for YBCO and a potential substrate material for the deposition of YBCO films. Also, it is a promising material for use as a container for processing bulk material, and as a crucible material for crystal growth. In addition, BaHfO, seems to be a more stable material than BaZrO,.
References [ 1] C.T. Cheung and E. Ruckenstein,
J. Mater. Res. 4 (1989)
I.
[ 21 L.A. Tietz and C.B. Carter, J. Mater. Res. 4 ( 1989) 1072. [3] B.R. Powell and R.L. Bloink. J. Mater. Sci. 26 ( 1991) 6507. [ 41 S. Kikkawa and F. Kanama~, J. Mater. Sci. Letters 1I (1992) 9. [ 51S.J. Lukasiewicz, J. Am. Ceram. Sot. 72 ( 1989) 617. [6] K. Masters, Spray drying, 4th Ed. (Wiley, New York, 1985).
333