Overview of our work on cation order in tunnel compounds. Presented on the ECM24 in Caen.

1. 1/48Hadermann
Cation ordering in tunnel
manganites solved by TEM
Joke Hadermann

2. 2/48Hadermann
Acknowledgements
Moscow State University: A.M. Abakumov,
M. Kovba, E.V. Antipov
CRISMAT, Ensicaen: L. Gillie, C. Martin, M.
Hervieu, O. Pérez, E. Suard
EMAT: G. Van Tendeloo

3. 3/48Hadermann
Overview
• Introduction:
- What are tunnel manganites?
- The possible frameworks (hosts) in a logical
order...
- The guests
• Generalization of the description and new
examples of tunnel manganites
- SrMn3O6
- CaMn3O6
- Todorokite with rock salt type tunnel contents

4. 4/48Hadermann
MnO6
octahedra
connect octahedra
into infinite chains
by edge sharing
What are tunnel manganites?
connect chains
by
edge- and/or
corner sharing in
a circular manner
chains of MnO6
octahedra
tunnel
framework

5. 5/48Hadermann
MnO6
Pyrolusite
Rutile-type tunnels
Indicated as "R“
1 x 1
Ref.: A.S. John, Phys.Rev.21(1923)389
a=b= 4.40 Å
c= 2.87 Å
Pyrolusite or β-MnO2: 1 x 1

6. 6/48Hadermann
Ref.: Bystroem, A.M., Acta Chemica Scandinavica (1949), 3, 163-173
Ramsdellite: 2 x 1
a= 4.46 Å
b= 9.32 Å
c= 2.85 Å

7. 7/48Hadermann
alpha-MnO2
Ref.: Kondrashev, Yu.D.;Zaslavskii, A.I.,
Izvestiya Akademii Nauk SSSR, Seriya Fizicheskaya (1951), 15, 179-186
Ramsdellite

8. 8/48Hadermann
Hollandite
Ref.: Bystroem, A.;Bystroem, A.M., Acta Crystallographica (1950), 3, 146-154
BaMn8O16
a= 4.46 Å
b= 9.32 Å
c= 2.85 Å

9. 9/48Hadermann
And in the same manner...
Pyrolusite Ramsdellite
Hollandite Romanechite
Todorokite
1 x 1 2 x 1
2 x 2 3 x 2
3 x 3
Woodruffite
4 x 3

10. 10/48Hadermann
Pyrolusite Ramsdellite Hollandite

11. 11/48Hadermann
Pyrolusite Ramsdellite Hollandite
approx.
2.85 Å

12. 12/48Hadermann
Marokite: hexagonal tunnels
Ref.: Lepicard, G.;Protas, J., Comptes Rendus Hebdomadaires des Seances de
l'Academie des Sciences (1964), 258, 1847-1849
CaMn2O4
a= 9.71 Å
b= 10.03 Å
c= 3.162 Å

13. 13/48Hadermann
More complex forms
Ref.:
N.Floros,C.Michel,
M.Hervieu,B.Raveau,JSSC
(2001), 162, 34-41
Na1.1Ca1.8Mn9O18Ba6Mn24O48
Ref.:
P.Boullay,M.Hervieu,
B.Raveau,
JSSC (1997), 132, 239-
248
CaMn4O8
Ref.: N.Barrier,C.Michel,
A.Maignan,M.Hervieu,
B.Raveau,
J. Mat. Chem.(2005), 15,
386-393

14. 14/48Hadermann
NaScTiO4: 8-shaped tunnels
A.F.Reid, A.D.Wadsley, M.J.Sienko, Inorganic
Chemistry (1968), 7, 112-118

15. 15/48Hadermann
More complex forms
Ref.:
N.Floros,C.Michel,
M.Hervieu,B.Raveau,JSSC
(2001), 162, 34-41
Na1.1Ca1.8Mn9O18Ba6Mn24O48
Ref.:
P.Boullay,M.Hervieu,
B.Raveau,
JSSC (1997), 132, 239-
248
CaMn4O8
Ref.: N.Barrier,C.Michel,
A.Maignan,M.Hervieu,
B.Raveau,
J. Mat. Chem.(2005), 15,
386-393

16. 16/48Hadermann
More complex forms
Ba6Mn24O48
Ref.:
P.Boullay,M.Hervieu,
B.Raveau,
JSSC (1997), 132, 239-
248
Ref.:
N.Floros,C.Michel,
M.Hervieu,B.Raveau,JSSC
(2001), 162, 34-41
Na1.1Ca1.8Mn9O18CaMn4O8
Ref.: N.Barrier,C.Michel,
A.Maignan,M.Hervieu,
B.Raveau,
J. Mat. Chem.(2005), 15,
386-393

17. 17/48Hadermann
The guest cations
AxMnO2
•Size of guests determines size and shape of tunnels
•The charges on the tunnel cations are balanced by
the substitution of some Mn+3 by Mn+4
Mn+3 - Mn+4 charge order in hollandite,
romanechite and todorokite
•Different repeat periods guest and framework
often incommensurately modulated

18. 18/48Hadermann
Overview
• Introduction:
- What are tunnel manganites?
- The possible frameworks (hosts) in a logical
order...
- The guests
• Generalization of the description and new
examples of tunnel manganites
- SrMn3O6
- CaMn3O6
- Todorokite with rock salt type tunnel contents

19. 19/48Hadermann
SrMn3O6: 8-shaped tunnels
Gillie et al., JSSC 177 (2004) 3383-3391

20. 20/48Hadermann
JSSC, 177 (2004) 3383
[001]
SrMn3O6

21. 21/48Hadermann
q= 0.52a* + 0.28c*
JSSC, 177 (2004) 3383
2000
0010
0001
0002
00032011
-
2011
2012
-
2013
-
2010
SrMn3O6

22. 22/48Hadermann
q= 0.52a* + 0.28c* q= 0.54a* + 0.29c*
q= 0.66a* + 0.33c*q= 0.52a* + 0.31c*
SrMn3O6
JSSC, 177
(2004) 3383

23. 23/48Hadermann
CaMn2O4
N.Barrier,C.Michel,A.Maignan,M.Hervieu,B.Raveau,
J. Mat. Chem.(2005), 15, 386-393
Lepicard, G.;Protas, J., Comptes Rendus Hebdomadaires
des Seances de l'Academie des Sciences (1964), 258,
1847-1849
m=2
CaMn2O4
literature
CaMnmO2m
m=3
CaMn3O6
this work
m=4
CaMn4O8
literature
CaMn4O8
CaMn3O6

24. 24/48Hadermann
CaMn2O4
CaMn3O6
Hadermann et al., Chem. Mater, 18 (2006) 5530

25. 25/48Hadermann
Hadermann et al., Chem. Mater, 18 (2006) 5530
CaMn3O6

26. 26/48Hadermann
Sub a*
Sub c*
CaMn3O6=
Ca0.66Mn2O4
CaMn3O6
2/3 of
Ca-positions
occupied
Hadermann et al., Chem. Mater,
18 (2006) 5530

27. 27/48Hadermann
q= 2/3a* + 1/3 c*
Hadermann et al.,
Chem. Mater, 18 (2006)
5530
Subcell:
a=9.07Å
b=11.3 Å
c=2.83 Å
CaMn3O6

28. 28/48Hadermann
CaMn3O6:
q= 2/3a* + 1/3 c* γ= 0.33
Ca(1-0.33)/2MnO2= Ca0.33MnO2= Ca1Mn3O6
CaMn2O4:
c=3.162 Å
q= 0 c* γ= 0
Ca(1-0)/2MnO2= Ca0.5MnO2 = Ca1Mn2O4
The compositionally modulated
structure approach
CaMn4O8:
c=5.6474 Å
q= 1/2 c* γ= 0.5
Ca(1-0.5)/2Mn2O4= Ca0.25MnO2
=CaMn4O8
CaxMnO2
x= (1- γ )/2 Ca(1- γ)/2MnO2
J. Mat. Chem. 19 (18)2660

29. 29/48Hadermann
Orange=Mn+4-δO6 octahedra
Yellow=Mn+3+δO6 octahedra
Charge ordering stabilizes the structure
CaMn3O6
Hadermann et al.,
Chem. Mater, 18
(2006) 5530

30. 30/48Hadermann
CaMn3O6
CaMn2O4
The compositionally modulated
structure approach
CaMn4O8
x= (1- γ )/2 Ca(1- γ)/2MnO2
Fits for
Use same formula
Sr(1- γ)/2MnO2
for Sr1±δMn3O6
J. Mat. Chem. 19 (18), 2660

31. 31/48Hadermann
q= 0.52a* + 0.28c* q= 0.54a* + 0.29c*
q= 0.66a* + 0.33c*q= 0.52a* + 0.31c*
SrMn3O6

32. 32/48Hadermann
q= 0.66a* + 0.33c*
CaMn3O6:SrMn3O6:
q= 0.66a* + 0.33c*
SrMn3O6 versus CaMn3O6

33. 33/48Hadermann
q= 0.52a* + 0.28c* q= 0.54a* + 0.29c*
q= 0.66a* + 0.33c*q= 0.52a* + 0.31c*
Sr0.72Mn2O4 Sr0.71Mn2O4
Sr0.69Mn2O4 Sr0.66Mn2O4
=Sr1.08Mn3O6 =Sr1.07Mn3O6
=Sr1.04Mn3O6 =Sr1Mn3O6
SrMn3O6
x= (1- γ )/2
Sr(1- γ)/2MnO2

34. 34/48Hadermann
The composite structure approach
Two subsystems:
Framework
MnO2
Guest cations
A1-x
Subsystem I
c-parameter = c1
Subsystem II
c-parameter = c2
g=ha*+kb*+lc1*+mc2*
q=c2*= γ c1*
Ratio cell volumes= VI/VII = γ
c1*
c2*

35. 35/48Hadermann
Composite structure Ba6Mn24O48
Tetragonal, a=18.2 Å,
c1=2.8 Å and c2=4.6 Å
(a,c1) framework
(a,c2) barium ions
Ref.: P.Boullay,M.Hervieu,B.Raveau,
JSSC (1997), 132, 239-248

36. 36/48Hadermann
Framework
MnO2
Guest cations
Ax
Subsystem I
c-parameter = c1
Subsystem II
c-parameter = c2
q=c2*= γ c1*
p = number of octahedra in the average unit cell
r = number of A-cation columns in the average unit cell
General case: x= γ r / p
The composite structure approach

37. 37/48Hadermann
Example 1: Ba6Mn24O48
c1=2.8 Å and c2=4.6 Å so γ=0.609
p = 24
r = 10
So x= 0.609. 10 / 24 = 0.253
gives Ba0.253MnO2
is equal to Ba6.072Mn24O48
p = number of octahedra in the average unit cell
r = number of A-cation columns in the average unit cell
General case: x= γ r / p
The composite structure approach
1
2
3
4
5 6
78
γ

38. 38/48Hadermann
Example 2: CaMn4O8
literature c=5.6474 Å
so c1=2.823 and c2= 5.6474 Å= 2 c1
so γ=0.5
p = 16
r = 8
So x= 0.5 . 8 / 16 = 0.25
gives Ca0.25MnO2
is equal to CaMn4O8
p = number of octahedra in the average unit cell
r = number of A-cation columns in the average unit cell
General case: x= γ r / p
The composite structure approach

39. 39/48Hadermann
Framework
MnO2
Guest cations
A1-x
Subsystem I
c-parameter = c1
Subsystem II
c-parameter = c2
q=c2*= γ c1*
p = number of octahedra in the average unit cell
r = number of A-cation columns in the average unit cell
General case: x= γ r / p
Simplification for square tunnels?
(Hollandite, todorokite,…)
Square tunnels: x= γ m / 2 n
m = number of cation columns in the tunnel
n= number of chains in the bricks
The composite structure approach

40. 40/48Hadermann
[SrF0.82(OH)0.18]2.5[Mn6O12]

41. 41/48Hadermann
[SrF0.82(OH)0.18]2.5[Mn6O12]
a=9.7846(3) Å
c1=2.8406(1) Å c2=4.49 Å
q1=c2*=0.63181(3)c1*= γc1*

42. 42/48Hadermann
[SrF0.82(OH)0.18]2.5[Mn6O12]
Electron diffraction:
a=9.7846(3) Å
c1=2.8406(1) Å
c2=4.49 Å
q1=c2*=0.63181(3)c1*= γc1*
P42/m(00γ)s0
X-ray refinement:
guests in rock salt type
(NaCl) arrangement c
a

43. 43/48Hadermann
Average interplanar spacing 89 Å
a’=2a
q2=0.0176(1)a*+0.07497b*
b
a
Submitted to Chemistry of Materials
[SrF0.82(OH)0.18]2.5[Mn6O12]

44. 44/48Hadermann
The composite structure approach
Framework
MnO2
Guest cations
A1-x
Subsystem I
c-parameter = c1
Subsystem II
c-parameter = c2
q=c2*= γ c1*
Square tunnels: x= γ m / 2n
m = number of cation columns in the tunnel
n= number of chains in the bricks
p = number of octahedra in the average unit cell
r = number of A-cation columns in the average unit cell
General case: x= γ r / p
J. Mat. Chem. 19 (18) 2660

45. 45/48Hadermann
q=c2*= γ c1*
Square tunnels: x= γ m / 2n
n=number of chains in the brick
m = number of cation columns in the tunnel
Todorokite: q1=c2*=0.63181(3)c1*= γc1*
so γ = 0.63181
n = 3
m = 4
So x= 0.63181 . 4 / 2 .3 =0.421
gives [SrX]0.421MnO2
is equal to [SrX]2.53Mn6O12
The composite structure approach:
square tunnel simplification
J. Mat. Chem. 19 (18) 2660

46. 46/48Hadermann
q1=c2*=0.63181(3)c1*= γc1*
so γ = 0.63181
p = 6
r = 4
So x= 0.63181 . 4 / 6 = 0.421
gives [SrX]0.421MnO2
is equal to [SrX]2.53Mn6O12
p = number of octahedra in the average unit cell
r = number of A-cation columns in the average unit cell
General case: x= γ r / p
The composite structure approach:
q=c2*= γ c1*
Todorokite:
general formula
J. Mat. Chem. 19 (18) 2660

47. 47/48Hadermann
Conclusions
• The first manganite analogue of NaFeTiO4 is
synthesized: SrMn3O6
• The compound CaMn3O6 is synthesized and
turns out to have a CaMn2O4 framework
• The ordering of Ca with vacancies in the
tunnels is derived from the modulation vector
• A general formula is proposed to calculate the
composition of the different phases directly
from the modulation vector
A(1- γ)/2MnO2
- fits CaxMnO2 and SrxMnO2 compounds

48. 48/48Hadermann
Conclusions
• A new todorokite type phase is presented,
containing 4 cation columns instead of the
traditional 1: rock salt type ordered guest
• The general formula for determining the
composition directly from the ratio of the two c-
parameters in a composite structure is
AxMnO2 with x= γ r / p
r= # A-cations, p = # octahedra
• A simplified form for square tunnels:
AxMnO2 with x= γ m / 2n
m= # A-cations, n = # chains in brick