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The structure of a high temperature phase in a cationic conductor, KAlSi2O6
SOLID
ElSEVIER
Solid State Ionics 79 (1995) 120-123
STATE IONICS
The structure of a high temperature phase in a cationic conductor, KAlSi,O, Yoshiaki Ito a2*, Scott Kuehner b, Subrata Ghose b aInstitute for Chemical Research, Kyoto Uniuersity, Vji, Kyoto 611, Japan b Mineral Physics Group, Department of Geological Science, University of Washington, Seattle, WA 98195, USA
Abstract The crystal structure of the high temperature phase of KAlSi,O, at 700°C has been refined to R(%) = 5.4 by the least-squares method using 309 reflections. The thermal oscillation of K atom is great and the equivalent temperature factor B,, = 15.871(27) A2. One of the principal axes of the thermal ellipsoids in K atom is close to the [ill] direction and the magnitude of rms amplitude in this axis is larger than in other axes. Keywordr:
Crystal structure; Ionic conduction;
X-ray diffraction;
Phase transition
1. Introduction The phase transition of this compound has long been studied by many workers using a variety of techniques: X-ray [l-7], Neutron [8], DTA and DSC [9,10], and NMR [ 1 l-131. Two different conclusions on the phase transition of leucite have been presented. Peacor [l] reported that this material had a single transition due to changing from tetrahedral (14,/a) to cubic (Ia3d) structure. Sadanaga and Ozawa [2], however, concluded that this transition was the second-order type as they found no evidence of an abrupt thermodynamic change (small peak in DTA [9]) at the transition. Furthermore, Mazzi et al. [4] analyzed a low temperature form of leucite proposed as space group 14,/a, but they were unable to obtain good structural analysis due to presence of twinning. * Corresponding
author.
0167-2738/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSDI 0167-2738(95)00041-O
Although it was considered that leucite had a transition from tetragonal (14,/a) to cubic (Ia3d) with an intermediate transient I4,/acd phase, recently, Ito et al. [7] observed the Bragg reflections of 200, 020, and 002 in the temperature range of 21900°C. This result suggests that the previous assumption that the space group for a low temperature form in the compound is 14,/a and one for a high temperature form being Ia3d is not correct. Ruscher et al. [14] reported on this compound that at low frequencies, dc conductivity is thermally activated with E, = 1.0 eV in the low temperature phase and the intermediate phase is characterised by a steep increase in conductivity which then shows a lower activation energy (0.5 eV) in the high temperature phase. In this work, the crystal structure of the high temperature phase of the compound was analyzed at 700°C in order to investigate the behaviour of the K ion at high temperature.
Y. Ito et al/Solid
2. Experimental X-ray diffraction measurements were made on a large (Huber 512) four-circle X-ray diffractometer (diameter of chi circle 520 mm) with MO target. The diffractometer was automated with a VAX 11/750 computer using electronics and computer programs developed by Strouse (University of California, Los Angeles). A crystal for X-ray study was formed into a spherical shape (diameter 0.30 mm) using a Bondtype grinder [151 and sealed in an evacuated quartz capillary. Single crystal diffractometer measurements showed this crystal to be composed of two pseudomerohedrically twinned individuals, the first and the second comprising each about 50%. A gas flow furnace was mounted on a x-y-z stage directly across from the goniometer cradle, which was offset 63.5 mm from the chi-circle plane. During the X-ray measurements the furnace and the goniometer cradle moved in tandem. This configuration allowed precise positioning of the furnace with respect to the crystal. Air flow was regulated through a flow valve at the rate of 2.0 l/min. The temperature calibration of the furnace was determined from the thermal expansion of NaCl [16] and the standard deviation in temperature was found within f6 K in the temperature range of room temperature to 900°C. The X-ray intensity data were measured up to 20 = 60” with a scan speed of 3”/min at 700°C. The intensity data were corrected for Lorentz and polar-
ization factors. Least square refinements were carried out using a full matrix least-squares program (RFINEII [17]), and anisotropic temperature factors. The atomic scattering factors including anomalous dispersion for K, Al, Si, and 0 were taken from International Tables for X-ray Crystallography, IV [18]. The initial atomic positional coordinates were taken from Bell et al. [19] for refinement of the structure of the high temperature phase (Zu3). The unit cell dimensions used for the structure refinement, number of the reflections, and R-factor are listed in Table 1, part (a). The final atomic positional and thermal parameters are listed in Table 1 parts (b) and (cl.
3. Results and discussion As seen in Fig. 1, the lattice parameters a and c were clearly separated below 675°C (Z&) but indistinguishable at this temperature. Above Tc,, the lattice constants of the compound became metrically cubic. An intensity data set was obtained at 700°C. After data collection, the crystal was quenched to the room temperature by dropping the furnace voltage and current to zero, in order to check the property of the memory. The twin size was almost constant after the physical damage. We did not observe an abrupt increase or decrease in lattice parameters which would correspond to the I4 1/a-14, /acd transition
Table 1 Tbe results of the refinements at 700°C: (a) Crystallographic data of KAlSi,O,; orientations of principal axes of thermal ellipsoids of K ions Cell constant (A) Space group Number of independent
(a)
(b) atomic parameters
x Y z B =I
63
Axis
of KAlSi,O,
and (c) magnitudes
a, = 13.547 (20) Ia 309 5.4
reflections
R (%)
(b)
121
State Ionics 79 (1995) 120-123
K
Si
01
02
0.12508(80) 0.12508(80) 0.12508(80) 15.871(27)
0.12486(H) 0.66215(14) 0.58783(14) 3.881(7)
0.46995(36) 0.38359(43) 0.14524(49) 8.300(15)
0.13172(44) 0.71941(37) 0.10244(47) 8.18504)
RMS amplitude (A)
angle to +a
angle to + b
angle to + c
35.2 65.9 54.7
114.0 144.7 54.7
(“I 1 2 3
0.4350) 0.426(l) 0.491(2)
114.0 65.9 54.7
and
122
Y. Ito et aL/Solid
ti, :
i
00
+
r g
t
c 13.50
t t
State Ionics 79 (1995) 120-123
1ttttjtt itttii,(,
-
I’il”
+
E K
a
0 .o z 2
. 13.00
t
to
’
+ + + 1 jttiit
1 It tt’
Tc,
675’C
t
I 100
I
I 300
/
, !/,
I 500
I 700
900 , Cl
Fig. 1. Relationship
between
lattice parameters
and temperature
[71.
in Fig. 1. To confirm the existence of 14,/a-14,/a& transition (the first type) and 14,/a& Zu3d (the second type) in this material, The intensities of the reflections (200, 020, 002, 600, 060, 006, 202, 303) were measured as a function of temperature. 200, 020, and 002 reflections were observed throughout the temperature interval from 21°C to
750°C. However, the 600 and 060 reflections disappeared at 655°C CT,,; Fig 2a). Furthermore, the intensity of the 202 and 303 reflections decreased with increasing temperature, and above T,,, the 303 reflection disappeared while the 202 reflection became constant (Fig. 2b). Therefore, we have confirmed that there are two transition points in this compound, T,, and c, and it follows that the 14,/a low temperature form and the Zu3d high temperature form do not exist, but the space group for the low temperature phase is Ibcu and one for the high temperature phase being Zu3 is possible since the existence of both space groups cannot be confirmed due to the non-disappearance of the reflections of 200, 020 and 002. At 700°C the refined final parameters agree well with those reported by Peacor [ll. Regarding the ionic conduction mechanism, the behavior of K ions is very important: in Iu3. The framework structure of the compound has tunnels close to the cubic body
Reilectlona 0200 -020 '002 .600 -060 i A006
I 500
I 900
Fig. 2(a). Structure factor corresponding to integrated intensity as a function of temperature. At T,, = 655”C, the compound undergoes the transition from a low temperature to an intermediate form [7]; (b) structure factor corresponding to integrated intensity as a function of temperature. At T,, = 675”C, the compound undergoes the transition from an intermediate form to a high temperature form [7].
Y. Ito et al. /Solid
State Ionics 79 (1995) 120-123
diagonal directions. K ions are located in these tunnels between “bottlenecks” each formed by a ring of six comer-linked (Al,Si)O, tetrahedra. From the structure analysis results, rms amplitude of K ions is significantly larger in the (111) direction (Table 1, part (c)J. The tunnels do not intersect in the crystal structure, but they are connected by direct links between two K ions in two different tunnels 1141. Therefore, it may be proposed that the high ionic conductivity is due to K ions migration along these directions.
Acknowledgements Y.I. is indebted to Prof. Thomas Dunne, University of Washington, Dr. Kevin Kveton, Chevron Company and Mr. Hiraku Ito, Mrs. Mieko Ito, and Prof. Kichiro Koto of Tokushima University for continuous encouragement, and also wishes to express his thanks to Mr. Roger Baker for his advice and maintenance of the Huber four-circle diffractometer.
References [l] D.R. Peacor, Z. Kristallogr. 127 (1968) 218. [2] R. Sadanaga and T. Ozawa, Miner. J. Japan 5 (1968) 321.
123
[31 M. Korekawa, Z. Kristallogr. 129 (1969) 343. [41 F. Mazzi, E. Galli and G. Gottardi, Am. Miner. 61 (1976) 108.
[51 D.C. Palmer, E.K.H. Salje and W.W. Schmahl, Phys. Chem. Miner. 16 (1988) 71.
161D.C. Palmer, E.K.H. Salje and W.W. Schmahl, Phys. Chem. Miner. 16 (1988) 298.
[71 Y. Ito, S. Kehner and S. Ghose, Z. Kristallogr.
197 (1991) 75. b31H. Boysen, Phase Transitions in Ferroelastic and &elastic Crystals, Cambridge Topics in Mineral Physics and Chemistry, ed. E.K.H. Salje (Cambridge University Press, Cambridge, 1990) p. 334. [91 G.T. Faust, Schweiz.Mineral Petrogr. Mitt. 43 (1963) 165. [lOI R.A. Lange, 1.S.E. Carmichael and J.F. Stebbins, Am. Mineral. 71 (1986) 937. illI I.W.M. Brown, C.M. Cardile, K.J.D. Mackenzie, M.J. Ryan and R.H. Meinhold, Phys. Chem. Minerals. 15, 78 (1987). 1121J.B. Murdoch, J.F. Stebbins, I.S.E. Carmichael, and A. Pines, Phys. Chem. Miner. 15 (1988) 370. [131 B.L. Phillips, R.J. Kirkpatrick and A. Putunis, Phys. Chem. Miner. 16 (19891 591. [141 C. Ruscher, M. Papendick, H. Boysen, A. Putnis and E. Salje, Z. Kristallogr. 179 (1987) 195. [151 W.L. Bond, Rev. Sci. Instrum. 22 (1951) 334. b51 D.E. Enck and G. Dommel, J. Appl. Phys. 55 (1965) 1963. [171 L.W. Finger, RFINE II, a Fortran IV computer program for structure factor calculation and least-squares refinement of crystal structures. (Geophys. Lab., Carnegie Inst. of Washington, Washington DC, 1972). Vol. IV [I81 International Tables for X-ray Crystallography. (Kynoch Press, Birmingham, 1974). 1191A.M.T. Bell, C.M.B. Henderson, S.A.T. Redfern, R.J. Cernik, P.E. Champness, A.N. Fitch and S.C. Kohn, Acta Cryst. B50 (1994) 31.
ElSEVIER
Solid State Ionics 79 (1995) 120-123
STATE IONICS
The structure of a high temperature phase in a cationic conductor, KAlSi,O, Yoshiaki Ito a2*, Scott Kuehner b, Subrata Ghose b aInstitute for Chemical Research, Kyoto Uniuersity, Vji, Kyoto 611, Japan b Mineral Physics Group, Department of Geological Science, University of Washington, Seattle, WA 98195, USA
Abstract The crystal structure of the high temperature phase of KAlSi,O, at 700°C has been refined to R(%) = 5.4 by the least-squares method using 309 reflections. The thermal oscillation of K atom is great and the equivalent temperature factor B,, = 15.871(27) A2. One of the principal axes of the thermal ellipsoids in K atom is close to the [ill] direction and the magnitude of rms amplitude in this axis is larger than in other axes. Keywordr:
Crystal structure; Ionic conduction;
X-ray diffraction;
Phase transition
1. Introduction The phase transition of this compound has long been studied by many workers using a variety of techniques: X-ray [l-7], Neutron [8], DTA and DSC [9,10], and NMR [ 1 l-131. Two different conclusions on the phase transition of leucite have been presented. Peacor [l] reported that this material had a single transition due to changing from tetrahedral (14,/a) to cubic (Ia3d) structure. Sadanaga and Ozawa [2], however, concluded that this transition was the second-order type as they found no evidence of an abrupt thermodynamic change (small peak in DTA [9]) at the transition. Furthermore, Mazzi et al. [4] analyzed a low temperature form of leucite proposed as space group 14,/a, but they were unable to obtain good structural analysis due to presence of twinning. * Corresponding
author.
0167-2738/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSDI 0167-2738(95)00041-O
Although it was considered that leucite had a transition from tetragonal (14,/a) to cubic (Ia3d) with an intermediate transient I4,/acd phase, recently, Ito et al. [7] observed the Bragg reflections of 200, 020, and 002 in the temperature range of 21900°C. This result suggests that the previous assumption that the space group for a low temperature form in the compound is 14,/a and one for a high temperature form being Ia3d is not correct. Ruscher et al. [14] reported on this compound that at low frequencies, dc conductivity is thermally activated with E, = 1.0 eV in the low temperature phase and the intermediate phase is characterised by a steep increase in conductivity which then shows a lower activation energy (0.5 eV) in the high temperature phase. In this work, the crystal structure of the high temperature phase of the compound was analyzed at 700°C in order to investigate the behaviour of the K ion at high temperature.
Y. Ito et al/Solid
2. Experimental X-ray diffraction measurements were made on a large (Huber 512) four-circle X-ray diffractometer (diameter of chi circle 520 mm) with MO target. The diffractometer was automated with a VAX 11/750 computer using electronics and computer programs developed by Strouse (University of California, Los Angeles). A crystal for X-ray study was formed into a spherical shape (diameter 0.30 mm) using a Bondtype grinder [151 and sealed in an evacuated quartz capillary. Single crystal diffractometer measurements showed this crystal to be composed of two pseudomerohedrically twinned individuals, the first and the second comprising each about 50%. A gas flow furnace was mounted on a x-y-z stage directly across from the goniometer cradle, which was offset 63.5 mm from the chi-circle plane. During the X-ray measurements the furnace and the goniometer cradle moved in tandem. This configuration allowed precise positioning of the furnace with respect to the crystal. Air flow was regulated through a flow valve at the rate of 2.0 l/min. The temperature calibration of the furnace was determined from the thermal expansion of NaCl [16] and the standard deviation in temperature was found within f6 K in the temperature range of room temperature to 900°C. The X-ray intensity data were measured up to 20 = 60” with a scan speed of 3”/min at 700°C. The intensity data were corrected for Lorentz and polar-
ization factors. Least square refinements were carried out using a full matrix least-squares program (RFINEII [17]), and anisotropic temperature factors. The atomic scattering factors including anomalous dispersion for K, Al, Si, and 0 were taken from International Tables for X-ray Crystallography, IV [18]. The initial atomic positional coordinates were taken from Bell et al. [19] for refinement of the structure of the high temperature phase (Zu3). The unit cell dimensions used for the structure refinement, number of the reflections, and R-factor are listed in Table 1, part (a). The final atomic positional and thermal parameters are listed in Table 1 parts (b) and (cl.
3. Results and discussion As seen in Fig. 1, the lattice parameters a and c were clearly separated below 675°C (Z&) but indistinguishable at this temperature. Above Tc,, the lattice constants of the compound became metrically cubic. An intensity data set was obtained at 700°C. After data collection, the crystal was quenched to the room temperature by dropping the furnace voltage and current to zero, in order to check the property of the memory. The twin size was almost constant after the physical damage. We did not observe an abrupt increase or decrease in lattice parameters which would correspond to the I4 1/a-14, /acd transition
Table 1 Tbe results of the refinements at 700°C: (a) Crystallographic data of KAlSi,O,; orientations of principal axes of thermal ellipsoids of K ions Cell constant (A) Space group Number of independent
(a)
(b) atomic parameters
x Y z B =I
63
Axis
of KAlSi,O,
and (c) magnitudes
a, = 13.547 (20) Ia 309 5.4
reflections
R (%)
(b)
121
State Ionics 79 (1995) 120-123
K
Si
01
02
0.12508(80) 0.12508(80) 0.12508(80) 15.871(27)
0.12486(H) 0.66215(14) 0.58783(14) 3.881(7)
0.46995(36) 0.38359(43) 0.14524(49) 8.300(15)
0.13172(44) 0.71941(37) 0.10244(47) 8.18504)
RMS amplitude (A)
angle to +a
angle to + b
angle to + c
35.2 65.9 54.7
114.0 144.7 54.7
(“I 1 2 3
0.4350) 0.426(l) 0.491(2)
114.0 65.9 54.7
and
122
Y. Ito et aL/Solid
ti, :
i
00
+
r g
t
c 13.50
t t
State Ionics 79 (1995) 120-123
1ttttjtt itttii,(,
-
I’il”
+
E K
a
0 .o z 2
. 13.00
t
to
’
+ + + 1 jttiit
1 It tt’
Tc,
675’C
t
I 100
I
I 300
/
, !/,
I 500
I 700
900 , Cl
Fig. 1. Relationship
between
lattice parameters
and temperature
[71.
in Fig. 1. To confirm the existence of 14,/a-14,/a& transition (the first type) and 14,/a& Zu3d (the second type) in this material, The intensities of the reflections (200, 020, 002, 600, 060, 006, 202, 303) were measured as a function of temperature. 200, 020, and 002 reflections were observed throughout the temperature interval from 21°C to
750°C. However, the 600 and 060 reflections disappeared at 655°C CT,,; Fig 2a). Furthermore, the intensity of the 202 and 303 reflections decreased with increasing temperature, and above T,,, the 303 reflection disappeared while the 202 reflection became constant (Fig. 2b). Therefore, we have confirmed that there are two transition points in this compound, T,, and c, and it follows that the 14,/a low temperature form and the Zu3d high temperature form do not exist, but the space group for the low temperature phase is Ibcu and one for the high temperature phase being Zu3 is possible since the existence of both space groups cannot be confirmed due to the non-disappearance of the reflections of 200, 020 and 002. At 700°C the refined final parameters agree well with those reported by Peacor [ll. Regarding the ionic conduction mechanism, the behavior of K ions is very important: in Iu3. The framework structure of the compound has tunnels close to the cubic body
Reilectlona 0200 -020 '002 .600 -060 i A006
I 500
I 900
Fig. 2(a). Structure factor corresponding to integrated intensity as a function of temperature. At T,, = 655”C, the compound undergoes the transition from a low temperature to an intermediate form [7]; (b) structure factor corresponding to integrated intensity as a function of temperature. At T,, = 675”C, the compound undergoes the transition from an intermediate form to a high temperature form [7].
Y. Ito et al. /Solid
State Ionics 79 (1995) 120-123
diagonal directions. K ions are located in these tunnels between “bottlenecks” each formed by a ring of six comer-linked (Al,Si)O, tetrahedra. From the structure analysis results, rms amplitude of K ions is significantly larger in the (111) direction (Table 1, part (c)J. The tunnels do not intersect in the crystal structure, but they are connected by direct links between two K ions in two different tunnels 1141. Therefore, it may be proposed that the high ionic conductivity is due to K ions migration along these directions.
Acknowledgements Y.I. is indebted to Prof. Thomas Dunne, University of Washington, Dr. Kevin Kveton, Chevron Company and Mr. Hiraku Ito, Mrs. Mieko Ito, and Prof. Kichiro Koto of Tokushima University for continuous encouragement, and also wishes to express his thanks to Mr. Roger Baker for his advice and maintenance of the Huber four-circle diffractometer.
References [l] D.R. Peacor, Z. Kristallogr. 127 (1968) 218. [2] R. Sadanaga and T. Ozawa, Miner. J. Japan 5 (1968) 321.
123
[31 M. Korekawa, Z. Kristallogr. 129 (1969) 343. [41 F. Mazzi, E. Galli and G. Gottardi, Am. Miner. 61 (1976) 108.
[51 D.C. Palmer, E.K.H. Salje and W.W. Schmahl, Phys. Chem. Miner. 16 (1988) 71.
161D.C. Palmer, E.K.H. Salje and W.W. Schmahl, Phys. Chem. Miner. 16 (1988) 298.
[71 Y. Ito, S. Kehner and S. Ghose, Z. Kristallogr.
197 (1991) 75. b31H. Boysen, Phase Transitions in Ferroelastic and &elastic Crystals, Cambridge Topics in Mineral Physics and Chemistry, ed. E.K.H. Salje (Cambridge University Press, Cambridge, 1990) p. 334. [91 G.T. Faust, Schweiz.Mineral Petrogr. Mitt. 43 (1963) 165. [lOI R.A. Lange, 1.S.E. Carmichael and J.F. Stebbins, Am. Mineral. 71 (1986) 937. illI I.W.M. Brown, C.M. Cardile, K.J.D. Mackenzie, M.J. Ryan and R.H. Meinhold, Phys. Chem. Minerals. 15, 78 (1987). 1121J.B. Murdoch, J.F. Stebbins, I.S.E. Carmichael, and A. Pines, Phys. Chem. Miner. 15 (1988) 370. [131 B.L. Phillips, R.J. Kirkpatrick and A. Putunis, Phys. Chem. Miner. 16 (19891 591. [141 C. Ruscher, M. Papendick, H. Boysen, A. Putnis and E. Salje, Z. Kristallogr. 179 (1987) 195. [151 W.L. Bond, Rev. Sci. Instrum. 22 (1951) 334. b51 D.E. Enck and G. Dommel, J. Appl. Phys. 55 (1965) 1963. [171 L.W. Finger, RFINE II, a Fortran IV computer program for structure factor calculation and least-squares refinement of crystal structures. (Geophys. Lab., Carnegie Inst. of Washington, Washington DC, 1972). Vol. IV [I81 International Tables for X-ray Crystallography. (Kynoch Press, Birmingham, 1974). 1191A.M.T. Bell, C.M.B. Henderson, S.A.T. Redfern, R.J. Cernik, P.E. Champness, A.N. Fitch and S.C. Kohn, Acta Cryst. B50 (1994) 31.