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Control of phase transition in TaSe3
Mat. Res. B u l l . , Vol. 22, p p . 1341-1345, 1987. P r i n t e d i n t h e USA. 0025-5408/87 $3.00 + .00 C o p y r i g h t (c) 1987 P e r g a m o n J o u r n a l s Ltd.
CONTROL OF PHASE TRANSITION IN TaSe 3
K.Hayashi, A.Kawamura and K.Komai Laboratory for Solid State Chemistry Okayama University of Science 1-1,Ridai-cho, Okayama, Japan
(Received April I I ,
1986; R e f e r e e d )
ABSTRACT Stabilization factors of the high and low temperature phases of TaSe 3 are investigated. The low temperature phase is stabilized by zirconium or titanium impurity. The high temperature phase is stabilized by oxygen impurity. Without oxygen impurity, the low temperature phase is stable up to decomposition temperature and the phase transition is completely suppressed by zirconium impurity. MATERIALS INDEX:
selenides,
tantalum
INTRODUCTION Transition metal trichalcogenides have been extensively investigated in terms of crystal structures,charge density waves, superconductivity and other exotic properties(l,2). The crystal structures of transition metal trichalcogenides are constructed with the trigonal prismatic (MX3)n chains. Three types of the structures, ZrSe3(3),NbSe3(4),and TaSe3(5) types have been determined. Each structure is distinguished with arrangement of the (MX3)n chains. Recently a new phase of TaSe3 was prepared under high selenium pressure(6,7). The crystal structure of the new phase was supposed the NbSe3-1ike structure, but the crystal structure of this new phase has never been confirmed yet. The superconductivity on-set temperature of this new phase is slightly higher than that of the conventional phase(8). It is necessary to grow single crystals for developing the above studies. Before growing crystals it is necessary to know the stability of the phases. In the present investigation, the stabilization factors of the new and the conventional phases are investigated andthe stable region of each phase is determined. It is suggested that the new phase can be stabilized up to high temperature not only by high selenium pressure but also by impurity doping.
1341
1342
K.
HAYASHI,
e t al.
Vol.
22,
No.
10
EXPERIMENTAL preparation: The low temperature phase of TaSe3 was prepared in the following procedure; The stoichiometric mixture of tantalum metal powder(99.9%,Wako) and selenium shot(6N,Wako) was sealed in a silica glass tube under vacuum. This mixture was heated at 320"C for one week and the reaction was completed at 430°C for one week. After quenching the low temperature phase was obtained. The high temperature phase of TaSe3 was prepared by heating the low temperature phase above 450eC for several days. The low temperature phase of ZrxTal-xSe S was prepared by the following procedure; The zirconium metal powder(99.9%,Wako), the tantalum metal powder, and the selenium shot were mixed in the calculated ratio(x:O.05, 0.i0, 0.20, and 0.30). The mixture was heated in a silica glass ampoule at 320°C for one week and reaction completed at 500°C for one week. After quenching, ZrxTal-xSe3 sample was obtained. The impurity gas doping was performed by the following procedure; The various gases and liquid(H2, H20, 02, and CHsOH : 0.005 molt each) were introduced into a silica glass tube with metal trichaleogenide sample. Then the tube was sealed and heated at desired temperatures(between 500"C and 800°C) for one week. The Se/Metal ratio was determined by combustion method. The Zr/Ta ratio of the starting charge was taken to be that of the product. The decomposition temperature of ZrxTal-xSe3 was determined by DTA(heating rate; lO°C/min.). The phases were identified and the lattice parameters determined by powder X-ray diffraction(NBS method; using Si-standard). RESULTS AND DISCUSSION Phase transition in pure TaSe3: The phase transition from the low temperature phase to the high temperature phase is very sluggish in TaSe3, and it is impossible to detect this phase transition by DTA. Usually two days heating is necessary for completing the phase transition from the low temperature phase to the high temperature phase. This phase transition is considered irreversible in the present experimental limit; No trace of the phase transition from the high temperature phase to the low temperature phase is found in TaSes sample after one week at 400°C. This phase transition temperature is not affected by a small excess of selenium. The Se/Ta ratio of the present sample is 2.98(2.9 by Kikkawa(7); His high pressure sample decomposed at 250°C but the same phase was prepared at 450°C under normal pressure.). Phase transition in zirconium substituted TaSes(ZrxTal-xSe3): The powder X-ray diffraction pattern of the low temperature phase of ZrxTal-xSe S is similar to that of the low temperature phase of the pure TaSe3 sample(see Table I in reference(6).). This low temperature phase of ZrxTal-xSe3 sample is very stable. No ZrxTal-xSe3 sample(x:O.05, 0.i0, 0.20,and 0.30) shows the phase transition from the low temperature phase to high temperature phase. The selenium deficient sample, Zro.2Tao.8Se S is not transformed into the high temperature phase. The low temeprature phase of ZrxTal-xSe3 decomposes into diselenides and selenium without passing the high temperature phase. The decomposition proceeds in two steps(DTA curve is shown in Fig. i.). In the first step, ZrxTal-xSeS decomposes into ZrxTal-xSe 2 and Se. Then in the second step, the diselenide ZrxTal_xSe2 decomposes into two diselenides, ZrSe2 and TaSe2. The decomposition temperature of ZrxTal-xSe3 is shown in Fig.2. The decomposition temperature is slightly raised up by increasing the zirconium concentration. This decomposition tempera-
Vol. 22, No.
10
TaSe 3
1343
800
DISELENIDE ~. Se
700'
g
720
600
]E
L - PHASE
w
.lt-
-
0r-t z
3
500
I,U
760 800 Temperat ure('13)
Fig. i. DTA curves of TaSe3 and ZrxTal_xSe3 in decomposition.
400
J i , 0.1 0.2 0.3 X of ZrxTal_xSe 3
Fig. 2. Decomposition temperature of the low temperature phase of ZrxTal_xSe 3 without oxygen impurity.
ture was determined by DTA. Therefore the equilibrium value may be smaller than the value obtained by DTA(about 30°C lower). The low temperature phase of TaSe3 is also stabilized by titanium substitution. In the Tio.osTao.95Se3 sample, the low temperature phase is stable and phase transition is absent up to the decomposition temperature. The T i x T a l - x S e 3 ( x ~ O . l ) sample could not be prepared. A limit of titanium substitution may exist in TixTal_xSe 3. Those IVa transition metal substituted TaSe3 samples show no phase transition and only the low temperature phase is observed below the decomposition temperature. Revival of the phase transition in the ZrxTal-xSe3 samples by oxygen impurity: The impurity doping experiments reveal that oxygen impurity can induce the phase transition in the ZrxTal-xSe3 samples. After doping with oxygen and heating at 700°C, the low temperature phase of ZrxTal_xSe 3 sample is transformed into the high temperature phase. The powder X-ray diffraction pattern of the high temperature phase of Z r x T a l - x S e 3 ( x ~ 0 . 2 ) is similar to that of the high temperature phase of the pure TaSe 3 sample. Therefore the low temperature phase of ZrxTal-xSe 3 is surely transformed into the high temperature phase. The transition temperature versus x diagram is shown in Fig. 3. The transition temperature is raised as the x-value increases. The transition temeprature varies from 450°C to 715°C according to thex-value variation from 0.0 to 0.2 in ZrxTal-xSe3. This tendency of the transition temperature is also evidence for the stabilization of the low temperature phase of ZrxTal-xSe3 by zirconium substitution. In Fig. 3, the decomposition temperature of the high temperature phase is also plotted. This decomposition temeprature is same as that of the
1344
800
K. HAYASHI,
A
DISELENIDE ÷ Se
-j
60o L - PHASE 500
40(
I
I
0.! 0.2 X of Z~Tal_xSe 3
Vol.
I
03
Fig. 3. Phase transition temperature of ZrxTal_xSe 3 with oxygen impurity.
L- ZrxTa,-xSe3 I0.0£
Fig. 4. Variation of lattice parameters of the low temperature phase(L) and the high 3.50 temperature phase(H) of the ~A)3.48 ZrxTal-xSe3" 3.4( 15.6~ 15.67 c ~)]5.65 15.63
0 0
0
0
0
3.511" 3.50F 3.491"
0
O
O
o O
o o
o
o 0
9.841" 9.83 I-
106.6F ]06.4F }06.2F I06.0F
0 0
o~0 oi, o12 o13 X of ZrxTa1-xSe3
0 0
o o o
0
0 0
346}" 345}" 344F 343}-
51
o
o o
9.86}" 9.551"
0
51~ 51:
10.391"
0
I09.~
VC~)5 ~'
0
0
1 lO.C I09~
~(')109.E
0
H-Zrx Tal- xSe3 10.42t~0.41 I10.401-
0
O(A)K).04 10.02 10.00
22, No. i 0
low temperature phase within experimental error(±5~C). In the figure both the decomposition temperature and the phase transition temperature are raised by zirconium substitution, and the phase transition temeprature is more affected by zirconium substitution than the decomposition temeprature is. Therefore the high temeprature phase can be prepared in a wide temperature region at the low x-value of ZrxTal-xSe3. On the other hand the low temeprature phase can be prepared in a wide temperature region at high xvalue of ZrxTal-xSe3. Concerning the concentration of oxygen impurity, the oxygen impurity of 0.005moi% is desirable to induce the phase transition in ZrxTal-xSe3. The oxygen impurity less than 0.002 mol% cannot bring the phase transition in ZrxTal-xSe3 and the oxygen impurity more than 0.008 mol% produces a small amount of the zirconium oxide in ZrxTal-xSe3 sample. This result suggests that the stability of the high temperature phase depends on the concentration of the oxygen impurity but it is not certain that the transition temperature is also oxygen impurity-dependent.
H PHASE
700
et al.
0
o o
o
Slg~. 516
o
0~0
0'l O2 0'l~ ~I 3 X of ZrxTa1-xSe3
Vol.
22, No.
I0
TaSe 3
1345
The other impurities, hydrogen, methanol, and water, do not stabilize the high temperature phase and do not induce the phase transition in ZrxTal-xSe 3 samples. Only the oxygen impurity induces the phase transition and stabilizes the high temeprature phase in ZrxTal-xSe 3. Lattice parameters of ZrxTal-xSe3: The lattice parameters of the low temperature phase and the high temeprature phase of ZrxTal-xSe3(x~0.3) are shown in Fig. 4. In both phases, the b-parameter does not vary with zirconium concentration. The b-parameter represents the length of (TaSe3)n chain. Therefore the invariant b-parameter suggests that the length of (TaSe3)n chain is not affected by zirconium substitution in ZrxTal-xSe3. The a-parameter and the c-parameter of the high temperature phase become large as the x-value of ZrxTal-xSe3 increases. The a-parameter and the cparameter represent the interchain distances. Therefore the above result suggests that the interchain interaction of the high temperature phase becomes weak as the zirconium concentration increases. On the other hand the aparameter and the c-parameter of the low temperature phase become small as the x-value increases. This result suggests that the interchain interaction of the low temperature phase becomes large as the zirconium concentration increases. Consequently the stability of the low temperature phase may be enhanced as the zirconium concentration increases in ZrxTal-xSe 3. Those results are consistent with the fact that the phase transition temperature from the low temeprature phase to the high temperature phase is raised up by zirconium substitution. CONCLUSIONS The low temperature phase of TaSe 3 is stabilized up to the decomposition temperature by zirconium substitution. On the other hand the high temperature phase of the zirconium substituted TaSe3 is stabilized by oxygen impurity. The phase transition from the low temeprature phase to the high temeprature phase is induces by the oxygen impurity, but the transition temeprature is affected by the zirconium concentration of ZrxTal_xSe3( This phase transition is irreversible.). The stabilization of the low temperature phase by the zirconium substitution is also observed in the variation of the lattice parameters of ZrxTal_xSe 3. The length of (TaSe3)n chain is not affected by the zirconium substitution but the interchain distance of the low temperature phase becomes shorter with increasing the zirconium concentration. Thus the variation of the lattice parameters suggests that the interchain interaction of the low temperature phase is enhanced by the zirconiu~ substitution. The present results induced the direction of wreparation of the high and the low temperature phase of the tantalum triselenides by impurity control. REFERENCES 1. 2. 3. 4. 5. 6. 7. 8.
F.Hulliger "Structural Chemistry of Layered-Type Phases" D.Reidel, Dordrecht (1976) p247. P.Monceau, "Electronic Properties of Inorganic Quasi-one-Dimensional Compounds" part I and part II, D.Reidel, Dordrecht (198B). L.Brattas and A.Kjerkshus, Acta Chem.Scand., 26, 3441(1972). A.Meerchaut and J.Rouxel, J.Less-Common Metals, 39, 197(1975). A.Bjerkelund, J.H.Fermor and A.Kjerkshus, Acta Chem. Scand., 20, 1836(1966). S.Kikkawa, N.Ogawa, M.Koizumi and Y.Onuki, J.Solid State Chem., 41,31B(1982). S.Kikkawa, K.Shinya and M.Koizumi, J.Solid State Chem., 41, 323(1982). T.Sambongi, M.Yamamoto, K.Tsutsumi, Y.Shiozaki, K.Yamaya and Y.Abe, J.Phys. Soc. Jn., 42, 1421(1977).
CONTROL OF PHASE TRANSITION IN TaSe 3
K.Hayashi, A.Kawamura and K.Komai Laboratory for Solid State Chemistry Okayama University of Science 1-1,Ridai-cho, Okayama, Japan
(Received April I I ,
1986; R e f e r e e d )
ABSTRACT Stabilization factors of the high and low temperature phases of TaSe 3 are investigated. The low temperature phase is stabilized by zirconium or titanium impurity. The high temperature phase is stabilized by oxygen impurity. Without oxygen impurity, the low temperature phase is stable up to decomposition temperature and the phase transition is completely suppressed by zirconium impurity. MATERIALS INDEX:
selenides,
tantalum
INTRODUCTION Transition metal trichalcogenides have been extensively investigated in terms of crystal structures,charge density waves, superconductivity and other exotic properties(l,2). The crystal structures of transition metal trichalcogenides are constructed with the trigonal prismatic (MX3)n chains. Three types of the structures, ZrSe3(3),NbSe3(4),and TaSe3(5) types have been determined. Each structure is distinguished with arrangement of the (MX3)n chains. Recently a new phase of TaSe3 was prepared under high selenium pressure(6,7). The crystal structure of the new phase was supposed the NbSe3-1ike structure, but the crystal structure of this new phase has never been confirmed yet. The superconductivity on-set temperature of this new phase is slightly higher than that of the conventional phase(8). It is necessary to grow single crystals for developing the above studies. Before growing crystals it is necessary to know the stability of the phases. In the present investigation, the stabilization factors of the new and the conventional phases are investigated andthe stable region of each phase is determined. It is suggested that the new phase can be stabilized up to high temperature not only by high selenium pressure but also by impurity doping.
1341
1342
K.
HAYASHI,
e t al.
Vol.
22,
No.
10
EXPERIMENTAL preparation: The low temperature phase of TaSe3 was prepared in the following procedure; The stoichiometric mixture of tantalum metal powder(99.9%,Wako) and selenium shot(6N,Wako) was sealed in a silica glass tube under vacuum. This mixture was heated at 320"C for one week and the reaction was completed at 430°C for one week. After quenching the low temperature phase was obtained. The high temperature phase of TaSe3 was prepared by heating the low temperature phase above 450eC for several days. The low temperature phase of ZrxTal-xSe S was prepared by the following procedure; The zirconium metal powder(99.9%,Wako), the tantalum metal powder, and the selenium shot were mixed in the calculated ratio(x:O.05, 0.i0, 0.20, and 0.30). The mixture was heated in a silica glass ampoule at 320°C for one week and reaction completed at 500°C for one week. After quenching, ZrxTal-xSe3 sample was obtained. The impurity gas doping was performed by the following procedure; The various gases and liquid(H2, H20, 02, and CHsOH : 0.005 molt each) were introduced into a silica glass tube with metal trichaleogenide sample. Then the tube was sealed and heated at desired temperatures(between 500"C and 800°C) for one week. The Se/Metal ratio was determined by combustion method. The Zr/Ta ratio of the starting charge was taken to be that of the product. The decomposition temperature of ZrxTal-xSe3 was determined by DTA(heating rate; lO°C/min.). The phases were identified and the lattice parameters determined by powder X-ray diffraction(NBS method; using Si-standard). RESULTS AND DISCUSSION Phase transition in pure TaSe3: The phase transition from the low temperature phase to the high temperature phase is very sluggish in TaSe3, and it is impossible to detect this phase transition by DTA. Usually two days heating is necessary for completing the phase transition from the low temperature phase to the high temperature phase. This phase transition is considered irreversible in the present experimental limit; No trace of the phase transition from the high temperature phase to the low temperature phase is found in TaSes sample after one week at 400°C. This phase transition temperature is not affected by a small excess of selenium. The Se/Ta ratio of the present sample is 2.98(2.9 by Kikkawa(7); His high pressure sample decomposed at 250°C but the same phase was prepared at 450°C under normal pressure.). Phase transition in zirconium substituted TaSes(ZrxTal-xSe3): The powder X-ray diffraction pattern of the low temperature phase of ZrxTal-xSe S is similar to that of the low temperature phase of the pure TaSe3 sample(see Table I in reference(6).). This low temperature phase of ZrxTal-xSe3 sample is very stable. No ZrxTal-xSe3 sample(x:O.05, 0.i0, 0.20,and 0.30) shows the phase transition from the low temperature phase to high temperature phase. The selenium deficient sample, Zro.2Tao.8Se S is not transformed into the high temperature phase. The low temeprature phase of ZrxTal-xSe3 decomposes into diselenides and selenium without passing the high temperature phase. The decomposition proceeds in two steps(DTA curve is shown in Fig. i.). In the first step, ZrxTal-xSeS decomposes into ZrxTal-xSe 2 and Se. Then in the second step, the diselenide ZrxTal_xSe2 decomposes into two diselenides, ZrSe2 and TaSe2. The decomposition temperature of ZrxTal-xSe3 is shown in Fig.2. The decomposition temperature is slightly raised up by increasing the zirconium concentration. This decomposition tempera-
Vol. 22, No.
10
TaSe 3
1343
800
DISELENIDE ~. Se
700'
g
720
600
]E
L - PHASE
w
.lt-
-
0r-t z
3
500
I,U
760 800 Temperat ure('13)
Fig. i. DTA curves of TaSe3 and ZrxTal_xSe3 in decomposition.
400
J i , 0.1 0.2 0.3 X of ZrxTal_xSe 3
Fig. 2. Decomposition temperature of the low temperature phase of ZrxTal_xSe 3 without oxygen impurity.
ture was determined by DTA. Therefore the equilibrium value may be smaller than the value obtained by DTA(about 30°C lower). The low temperature phase of TaSe3 is also stabilized by titanium substitution. In the Tio.osTao.95Se3 sample, the low temperature phase is stable and phase transition is absent up to the decomposition temperature. The T i x T a l - x S e 3 ( x ~ O . l ) sample could not be prepared. A limit of titanium substitution may exist in TixTal_xSe 3. Those IVa transition metal substituted TaSe3 samples show no phase transition and only the low temperature phase is observed below the decomposition temperature. Revival of the phase transition in the ZrxTal-xSe3 samples by oxygen impurity: The impurity doping experiments reveal that oxygen impurity can induce the phase transition in the ZrxTal-xSe3 samples. After doping with oxygen and heating at 700°C, the low temperature phase of ZrxTal_xSe 3 sample is transformed into the high temperature phase. The powder X-ray diffraction pattern of the high temperature phase of Z r x T a l - x S e 3 ( x ~ 0 . 2 ) is similar to that of the high temperature phase of the pure TaSe 3 sample. Therefore the low temperature phase of ZrxTal-xSe 3 is surely transformed into the high temperature phase. The transition temperature versus x diagram is shown in Fig. 3. The transition temperature is raised as the x-value increases. The transition temeprature varies from 450°C to 715°C according to thex-value variation from 0.0 to 0.2 in ZrxTal-xSe3. This tendency of the transition temperature is also evidence for the stabilization of the low temperature phase of ZrxTal-xSe3 by zirconium substitution. In Fig. 3, the decomposition temperature of the high temperature phase is also plotted. This decomposition temeprature is same as that of the
1344
800
K. HAYASHI,
A
DISELENIDE ÷ Se
-j
60o L - PHASE 500
40(
I
I
0.! 0.2 X of Z~Tal_xSe 3
Vol.
I
03
Fig. 3. Phase transition temperature of ZrxTal_xSe 3 with oxygen impurity.
L- ZrxTa,-xSe3 I0.0£
Fig. 4. Variation of lattice parameters of the low temperature phase(L) and the high 3.50 temperature phase(H) of the ~A)3.48 ZrxTal-xSe3" 3.4( 15.6~ 15.67 c ~)]5.65 15.63
0 0
0
0
0
3.511" 3.50F 3.491"
0
O
O
o O
o o
o
o 0
9.841" 9.83 I-
106.6F ]06.4F }06.2F I06.0F
0 0
o~0 oi, o12 o13 X of ZrxTa1-xSe3
0 0
o o o
0
0 0
346}" 345}" 344F 343}-
51
o
o o
9.86}" 9.551"
0
51~ 51:
10.391"
0
I09.~
VC~)5 ~'
0
0
1 lO.C I09~
~(')109.E
0
H-Zrx Tal- xSe3 10.42t~0.41 I10.401-
0
O(A)K).04 10.02 10.00
22, No. i 0
low temperature phase within experimental error(±5~C). In the figure both the decomposition temperature and the phase transition temperature are raised by zirconium substitution, and the phase transition temeprature is more affected by zirconium substitution than the decomposition temeprature is. Therefore the high temeprature phase can be prepared in a wide temperature region at the low x-value of ZrxTal-xSe3. On the other hand the low temeprature phase can be prepared in a wide temperature region at high xvalue of ZrxTal-xSe3. Concerning the concentration of oxygen impurity, the oxygen impurity of 0.005moi% is desirable to induce the phase transition in ZrxTal-xSe3. The oxygen impurity less than 0.002 mol% cannot bring the phase transition in ZrxTal-xSe3 and the oxygen impurity more than 0.008 mol% produces a small amount of the zirconium oxide in ZrxTal-xSe3 sample. This result suggests that the stability of the high temperature phase depends on the concentration of the oxygen impurity but it is not certain that the transition temperature is also oxygen impurity-dependent.
H PHASE
700
et al.
0
o o
o
Slg~. 516
o
0~0
0'l O2 0'l~ ~I 3 X of ZrxTa1-xSe3
Vol.
22, No.
I0
TaSe 3
1345
The other impurities, hydrogen, methanol, and water, do not stabilize the high temperature phase and do not induce the phase transition in ZrxTal-xSe 3 samples. Only the oxygen impurity induces the phase transition and stabilizes the high temeprature phase in ZrxTal-xSe 3. Lattice parameters of ZrxTal-xSe3: The lattice parameters of the low temperature phase and the high temeprature phase of ZrxTal-xSe3(x~0.3) are shown in Fig. 4. In both phases, the b-parameter does not vary with zirconium concentration. The b-parameter represents the length of (TaSe3)n chain. Therefore the invariant b-parameter suggests that the length of (TaSe3)n chain is not affected by zirconium substitution in ZrxTal-xSe3. The a-parameter and the c-parameter of the high temperature phase become large as the x-value of ZrxTal-xSe3 increases. The a-parameter and the cparameter represent the interchain distances. Therefore the above result suggests that the interchain interaction of the high temperature phase becomes weak as the zirconium concentration increases. On the other hand the aparameter and the c-parameter of the low temperature phase become small as the x-value increases. This result suggests that the interchain interaction of the low temperature phase becomes large as the zirconium concentration increases. Consequently the stability of the low temperature phase may be enhanced as the zirconium concentration increases in ZrxTal-xSe 3. Those results are consistent with the fact that the phase transition temperature from the low temeprature phase to the high temperature phase is raised up by zirconium substitution. CONCLUSIONS The low temperature phase of TaSe 3 is stabilized up to the decomposition temperature by zirconium substitution. On the other hand the high temperature phase of the zirconium substituted TaSe3 is stabilized by oxygen impurity. The phase transition from the low temeprature phase to the high temeprature phase is induces by the oxygen impurity, but the transition temeprature is affected by the zirconium concentration of ZrxTal_xSe3( This phase transition is irreversible.). The stabilization of the low temperature phase by the zirconium substitution is also observed in the variation of the lattice parameters of ZrxTal_xSe 3. The length of (TaSe3)n chain is not affected by the zirconium substitution but the interchain distance of the low temperature phase becomes shorter with increasing the zirconium concentration. Thus the variation of the lattice parameters suggests that the interchain interaction of the low temperature phase is enhanced by the zirconiu~ substitution. The present results induced the direction of wreparation of the high and the low temperature phase of the tantalum triselenides by impurity control. REFERENCES 1. 2. 3. 4. 5. 6. 7. 8.
F.Hulliger "Structural Chemistry of Layered-Type Phases" D.Reidel, Dordrecht (1976) p247. P.Monceau, "Electronic Properties of Inorganic Quasi-one-Dimensional Compounds" part I and part II, D.Reidel, Dordrecht (198B). L.Brattas and A.Kjerkshus, Acta Chem.Scand., 26, 3441(1972). A.Meerchaut and J.Rouxel, J.Less-Common Metals, 39, 197(1975). A.Bjerkelund, J.H.Fermor and A.Kjerkshus, Acta Chem. Scand., 20, 1836(1966). S.Kikkawa, N.Ogawa, M.Koizumi and Y.Onuki, J.Solid State Chem., 41,31B(1982). S.Kikkawa, K.Shinya and M.Koizumi, J.Solid State Chem., 41, 323(1982). T.Sambongi, M.Yamamoto, K.Tsutsumi, Y.Shiozaki, K.Yamaya and Y.Abe, J.Phys. Soc. Jn., 42, 1421(1977).