Cation Ordering In Tunnel Compounds Determined By Tem

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

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Cation Ordering In Tunnel Compounds Determined By Tem

  1. 1. 1/48Hadermann Cation ordering in tunnel manganites solved by TEM Joke Hadermann
  2. 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. 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. 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. 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. 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. 7/48Hadermann alpha-MnO2 Ref.: Kondrashev, Yu.D.;Zaslavskii, A.I., Izvestiya Akademii Nauk SSSR, Seriya Fizicheskaya (1951), 15, 179-186 Ramsdellite
  8. 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. 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. 10/48Hadermann Pyrolusite Ramsdellite Hollandite
  11. 11. 11/48Hadermann Pyrolusite Ramsdellite Hollandite approx. 2.85 Å
  12. 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. 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. 14/48Hadermann NaScTiO4: 8-shaped tunnels A.F.Reid, A.D.Wadsley, M.J.Sienko, Inorganic Chemistry (1968), 7, 112-118
  15. 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. 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. 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. 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. 19/48Hadermann SrMn3O6: 8-shaped tunnels Gillie et al., JSSC 177 (2004) 3383-3391
  20. 20. 20/48Hadermann JSSC, 177 (2004) 3383 [001] SrMn3O6
  21. 21. 21/48Hadermann q= 0.52a* + 0.28c* JSSC, 177 (2004) 3383 2000 0010 0001 0002 00032011 - 2011 2012 - 2013 - 2010 SrMn3O6
  22. 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. 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. 24/48Hadermann CaMn2O4 CaMn3O6 Hadermann et al., Chem. Mater, 18 (2006) 5530
  25. 25. 25/48Hadermann Hadermann et al., Chem. Mater, 18 (2006) 5530 CaMn3O6
  26. 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. 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. 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. 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. 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. 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. 32/48Hadermann q= 0.66a* + 0.33c* CaMn3O6:SrMn3O6: q= 0.66a* + 0.33c* SrMn3O6 versus CaMn3O6
  33. 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. 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. 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. 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. 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. 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. 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. 40/48Hadermann [SrF0.82(OH)0.18]2.5[Mn6O12]
  41. 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. 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. 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. 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. 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. 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. 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. 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

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