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Ultrasonic investigations of the layered perovskite ceramic superconducting systems
Physica B 165&166 (1990) 1283-1284 North-Holland
ULTRASONIC INVESTIGATIONS OF THE LAYERED PEOOVSKITE CERAMIC SUPEROONDUCTING SYS'l»fS HE Yusheng, XIANG Jiong, JIN Sheng, HE Aisheng* and ZHANG Jincang**
Tsinghua University, Physics Department, Beijing, 100084, P.R. China *North University of Technology, Physics Division, Beijing, 100041, P.R. China **Henan Nonnal University, Physics Department, Xinxiang, 453002, P.R. China Ultrasonic measurements have been carried out on three type high T c perovskite ceramic superconductors La-Sr-Cu-o, Y-Ba-Cu-o and Bi(Pb)-Sr-Ca-eu-o. Anomalies in both sound velocity and attenuation of the above three systems were observed. The elastic constants and the Debye temperatures were also obtained and discussed.
1. INTRODUCTION The unit cells of the present superconducting multilayer perovskites can be represented in a universal formula as m(AO)+n(AOO3)' Systematic investigations of these three systems, e.g. Laa-.Sr.Cu04 (m:n=2:2), YBa aCu307-Y (m:n=0:3), (Bil-.Pb.)aSraCaCuzOs+ y (m:n=6:4) and (Bil-.Pb.)aSraCaaCu3010+Y (m:n=6:6) (hereafter referred to as LSCO, YBCO, B(P)SCCD 2212 and 2223 respectively), are necessary, not only to illuminate the similarities and differences between these systems, but also to reveal possible correlations between the superconducting and nonnal-state properties of high T c materials. 2. EXPERIMENTAL AND RESULTS
The samples studied were prepared by the standard method of solid state reaction. Ultrasonic measurements were carried out by using MATEC 7700 series equipnent. Details of the experimental techniques are the same as those discussed elsewhere (1). Typical results of ultrasonic attenuation of these three systems are stllllJl8rized in Table 1, 1~10
1.06 " - ' ,
o ~0.98
o .....
-
''!'r' "';~'4;1
~
1:0:11.02 o
II
B I _Yf J
;; 0.94
o
0.90
E/
I
FIGURE 1
Temperature dependence of elastic constants of La-Sr-eu-o system.
© 1990 -
1.05,~ G ~1.03 ~" : E~ :1.01.~.~ :::: 0.99
~ _./~ 0.86 ....' o 50 100 150200 250 300 Temperature (K)
0921-4526/90/$03.50
where Tpl, Tpz and ATp denote the temperatures of the first and the second anomalous attenuation peaks and the temperature hysteresis of the corresponding anomalous attenuation peaks between cooling and heating experiment;s. The longitudina"l and transverse sound velocities were also measured. Corrected to the void-free state by using the model given by Ledbetter and Datta (2) for the composite materials, the values of the following elastic constants: longitudinal modulus Ct, shear modulus G, bulk modulus B, Young's modulus E and Poisson ratio P and Debye Temperature On can be derived, and On is excellent agreement with that derived frOlll specific heat results On' (3) • Figures 1-4 show the typical temperature dependence of the elastic constants and Debye temperature On of the three systems. Table 2 summarized the superconducting transition temperature T c , the room temperature values of mass density D, sound velocity (Vt and VT) and the derived elastic constants, together with the corresponding parameters of the typical perovskite material SrTi03.
~
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~¥'
0.97
o•95
.-r:
.--,..I'
o
50 100 150 200 250 300 Temperature (K)
FIGURE 2
Temperature dependence of elastic constants of Y-Ba-eu-o system.
Elsevier Science Publishers B.V. (North-Holland)
Y. He,J.Xiang,S. nn,A.He,J. Zhang
1284
....:.J_~ <23
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1. 03
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;;1.Ql
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~~
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O. 871-......._ ........._-'-~~~..,.......,~ o 50 100 150 200 250 300 Temperature (K)
o
FIGURE 3
50 100 150 200 250 300 Temperature (K)
FIGURE 4
Temperature dependence of elastic constants of Bi(Pb)-Sr-<:a-Cu-o system.
Temperature dependence of Debye temperature of the three systems.
Table 1. VI trasonic anomalies ceramic superconductors
instability seems to be a cOlllllOn feature of all the three type perovskite ceramics, though the driving forces might be quite different from one to the other. The lattice instability seems very likely to appear at the temperatures near T=2T c, which is surprisingly similar to that of A15 compounds and may have close relation to their high T c • From Table 2, it can be seen that the differences between elastic constants for different perovskite families are striking (the shear modulus of SrTi03:LSCO:YBCO:BIP)SCCO =7.5: 3: 2.5: 1, nearly one order difference). The total layers Imtn) can be 1 (SrTi03), 3 (YBCO), 4 (lBCO) and 10-12 (B(P)SCCO), also one order difference. Such big difference in the nI.IIIbers of weakly interacting successive multilayers alOng c-axis can be expected to reduce the material stiffness dramatically. On the contrary, the values of the Poisson ratio P of all the perovskites studied are surprisingly close, suggesting that the dominant intra-layer interatomic bonding of these ceramics are very similar due to the similar intra-layer structure. Considering their T c increases from 0.1 K (for SrTiOs) to 110 K(for B(P)SCCO-2223l, it is thus suggested that the inter-layer interactions are the dominate forces for their high Tc superconductivity. Moreover, the opposite tendencies of 0 D of lBCO and YBCO result in a considerable difference in the low temperature values of OD, which also have some implications for the understanding of the mechanisms of their superconductivity.
lBCO YBCO
B(P)SCOO
TclK)
TpI(K)
38 90 80-110
75 160-180 200-210
of
high
Tc
~Tp(K)
235 250-270
/
o
10 30
Table 2. The elastic constants and related parameters of the metal-oxide superconductors. SrTi03 TdK)
<1
LSCO
YBCO
BSCCO 2212
38 90 74 6.22 5.69 5.35 Vdms-l) 8120 4834 4242 2846 VT(ms-1) 4800 2838 2599 1735 145 102 43.4 CdGPa) G(GPal 50.1 38.4 16.1 118 BIGPa) 78.5 51.2 21.9 180 124 92.2 38.8 190 E(GPa) P 0.23 0.24 0.20 0.20 OD(K) 410 480 250 690 OD'(K) 310-440 370-510 230-290
D(gcm- 3 ) 5.11
B(P)SCCO 2212 2223 80 5.02 2821 1784 39.9 16.0 18.6
37.3
0.17 270
108 4.35 2894 1813 36.4 14.3 17.4 33.7 0.18 280
4. DISCUSSIONS The different characteristics of the anomalies for each system can be attributed to the structure difference. The softening of sound velocity of LSCO near 100 K is accompanied with the tetragonal to orthorhombic transition and related to strong electron-phonon interaction (4), whereas for YBCO the ordering of oxygen vacancies in the one-dimensional chains leads to a broad attenuation peaks near 170 K (1), and the isothennal-like anomalous changes in both attenuation and velocity near 210 K in B(P)SCCO imply possible displacive fine structure changes, which may also relate to the superconductivity (5). However, the lattice
REFERENCES
II) (2)
(3) (4) (5)
Y.S. He et al, J. Phys. F17 (1987) L243. H.M. Ledbetter and S.K. Datta, J. Acoust. Soc. Am. 79 (20), 239 (1986). R.A. Fisher et al, J. Supercond. 10 (1989) L.F. Mattheiss, Phys. Rev. Lett. 58 (1987) 1028. Y.S. He et al. Phys. Rev. B40 (1989) 7384.
ULTRASONIC INVESTIGATIONS OF THE LAYERED PEOOVSKITE CERAMIC SUPEROONDUCTING SYS'l»fS HE Yusheng, XIANG Jiong, JIN Sheng, HE Aisheng* and ZHANG Jincang**
Tsinghua University, Physics Department, Beijing, 100084, P.R. China *North University of Technology, Physics Division, Beijing, 100041, P.R. China **Henan Nonnal University, Physics Department, Xinxiang, 453002, P.R. China Ultrasonic measurements have been carried out on three type high T c perovskite ceramic superconductors La-Sr-Cu-o, Y-Ba-Cu-o and Bi(Pb)-Sr-Ca-eu-o. Anomalies in both sound velocity and attenuation of the above three systems were observed. The elastic constants and the Debye temperatures were also obtained and discussed.
1. INTRODUCTION The unit cells of the present superconducting multilayer perovskites can be represented in a universal formula as m(AO)+n(AOO3)' Systematic investigations of these three systems, e.g. Laa-.Sr.Cu04 (m:n=2:2), YBa aCu307-Y (m:n=0:3), (Bil-.Pb.)aSraCaCuzOs+ y (m:n=6:4) and (Bil-.Pb.)aSraCaaCu3010+Y (m:n=6:6) (hereafter referred to as LSCO, YBCO, B(P)SCCD 2212 and 2223 respectively), are necessary, not only to illuminate the similarities and differences between these systems, but also to reveal possible correlations between the superconducting and nonnal-state properties of high T c materials. 2. EXPERIMENTAL AND RESULTS
The samples studied were prepared by the standard method of solid state reaction. Ultrasonic measurements were carried out by using MATEC 7700 series equipnent. Details of the experimental techniques are the same as those discussed elsewhere (1). Typical results of ultrasonic attenuation of these three systems are stllllJl8rized in Table 1, 1~10
1.06 " - ' ,
o ~0.98
o .....
-
''!'r' "';~'4;1
~
1:0:11.02 o
II
B I _Yf J
;; 0.94
o
0.90
E/
I
FIGURE 1
Temperature dependence of elastic constants of La-Sr-eu-o system.
© 1990 -
1.05,~ G ~1.03 ~" : E~ :1.01.~.~ :::: 0.99
~ _./~ 0.86 ....' o 50 100 150200 250 300 Temperature (K)
0921-4526/90/$03.50
where Tpl, Tpz and ATp denote the temperatures of the first and the second anomalous attenuation peaks and the temperature hysteresis of the corresponding anomalous attenuation peaks between cooling and heating experiment;s. The longitudina"l and transverse sound velocities were also measured. Corrected to the void-free state by using the model given by Ledbetter and Datta (2) for the composite materials, the values of the following elastic constants: longitudinal modulus Ct, shear modulus G, bulk modulus B, Young's modulus E and Poisson ratio P and Debye Temperature On can be derived, and On is excellent agreement with that derived frOlll specific heat results On' (3) • Figures 1-4 show the typical temperature dependence of the elastic constants and Debye temperature On of the three systems. Table 2 summarized the superconducting transition temperature T c , the room temperature values of mass density D, sound velocity (Vt and VT) and the derived elastic constants, together with the corresponding parameters of the typical perovskite material SrTi03.
~
,,'
~¥'
0.97
o•95
.-r:
.--,..I'
o
50 100 150 200 250 300 Temperature (K)
FIGURE 2
Temperature dependence of elastic constants of Y-Ba-eu-o system.
Elsevier Science Publishers B.V. (North-Holland)
Y. He,J.Xiang,S. nn,A.He,J. Zhang
1284
....:.J_~ <23
--
1. 03
1.07-~
;;1.Ql
E
l>:::
8CP)SCCO YBCO
~~
o
gO.99
g 0.99
u
o
.f-<
f-<
M'
.~
!LSCO
~
:::::r O • 95
::::: 0.97
,
z
~
~~O. 91
00.95
j
.'
o. 9 3~":.::··~·~_~-:-~~~!-::,-::~:--::-:!
O. 871-......._ ........._-'-~~~..,.......,~ o 50 100 150 200 250 300 Temperature (K)
o
FIGURE 3
50 100 150 200 250 300 Temperature (K)
FIGURE 4
Temperature dependence of elastic constants of Bi(Pb)-Sr-<:a-Cu-o system.
Temperature dependence of Debye temperature of the three systems.
Table 1. VI trasonic anomalies ceramic superconductors
instability seems to be a cOlllllOn feature of all the three type perovskite ceramics, though the driving forces might be quite different from one to the other. The lattice instability seems very likely to appear at the temperatures near T=2T c, which is surprisingly similar to that of A15 compounds and may have close relation to their high T c • From Table 2, it can be seen that the differences between elastic constants for different perovskite families are striking (the shear modulus of SrTi03:LSCO:YBCO:BIP)SCCO =7.5: 3: 2.5: 1, nearly one order difference). The total layers Imtn) can be 1 (SrTi03), 3 (YBCO), 4 (lBCO) and 10-12 (B(P)SCCO), also one order difference. Such big difference in the nI.IIIbers of weakly interacting successive multilayers alOng c-axis can be expected to reduce the material stiffness dramatically. On the contrary, the values of the Poisson ratio P of all the perovskites studied are surprisingly close, suggesting that the dominant intra-layer interatomic bonding of these ceramics are very similar due to the similar intra-layer structure. Considering their T c increases from 0.1 K (for SrTiOs) to 110 K(for B(P)SCCO-2223l, it is thus suggested that the inter-layer interactions are the dominate forces for their high Tc superconductivity. Moreover, the opposite tendencies of 0 D of lBCO and YBCO result in a considerable difference in the low temperature values of OD, which also have some implications for the understanding of the mechanisms of their superconductivity.
lBCO YBCO
B(P)SCOO
TclK)
TpI(K)
38 90 80-110
75 160-180 200-210
of
high
Tc
~Tp(K)
235 250-270
/
o
10 30
Table 2. The elastic constants and related parameters of the metal-oxide superconductors. SrTi03 TdK)
<1
LSCO
YBCO
BSCCO 2212
38 90 74 6.22 5.69 5.35 Vdms-l) 8120 4834 4242 2846 VT(ms-1) 4800 2838 2599 1735 145 102 43.4 CdGPa) G(GPal 50.1 38.4 16.1 118 BIGPa) 78.5 51.2 21.9 180 124 92.2 38.8 190 E(GPa) P 0.23 0.24 0.20 0.20 OD(K) 410 480 250 690 OD'(K) 310-440 370-510 230-290
D(gcm- 3 ) 5.11
B(P)SCCO 2212 2223 80 5.02 2821 1784 39.9 16.0 18.6
37.3
0.17 270
108 4.35 2894 1813 36.4 14.3 17.4 33.7 0.18 280
4. DISCUSSIONS The different characteristics of the anomalies for each system can be attributed to the structure difference. The softening of sound velocity of LSCO near 100 K is accompanied with the tetragonal to orthorhombic transition and related to strong electron-phonon interaction (4), whereas for YBCO the ordering of oxygen vacancies in the one-dimensional chains leads to a broad attenuation peaks near 170 K (1), and the isothennal-like anomalous changes in both attenuation and velocity near 210 K in B(P)SCCO imply possible displacive fine structure changes, which may also relate to the superconductivity (5). However, the lattice
REFERENCES
II) (2)
(3) (4) (5)
Y.S. He et al, J. Phys. F17 (1987) L243. H.M. Ledbetter and S.K. Datta, J. Acoust. Soc. Am. 79 (20), 239 (1986). R.A. Fisher et al, J. Supercond. 10 (1989) L.F. Mattheiss, Phys. Rev. Lett. 58 (1987) 1028. Y.S. He et al. Phys. Rev. B40 (1989) 7384.