Cation ordering in tunnel compounds determined by TEM

Cation ordering in tunnel manganites solved by TEM : 

Cation ordering in tunnel manganites solved by TEM Joke Hadermann

Acknowledgements : 

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

Overview : 

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

Slide 4: 

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

Slide 5: 

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

Slide 6: 

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

alpha-MnO2 : 

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

Hollandite : 

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

And in the same manner... : 

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

Slide 10: 

Pyrolusite Ramsdellite Hollandite

Slide 11: 

Pyrolusite Ramsdellite Hollandite approx. 2.85 Å

Marokite: hexagonal tunnels : 

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

More complex forms : 

More complex forms Ref.: N.Floros,C.Michel, M.Hervieu,B.Raveau,JSSC(2001), 162, 34-41 Na1.1Ca1.8Mn9O18 Ba6Mn24O48 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

NaScTiO4: 8-shaped tunnels : 

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

More complex forms : 

More complex forms Ref.: N.Floros,C.Michel, M.Hervieu,B.Raveau,JSSC(2001), 162, 34-41 Na1.1Ca1.8Mn9O18 Ba6Mn24O48 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

More complex forms : 

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 Na1.1Ca1.8Mn9O18 CaMn4O8 Ref.: N.Barrier,C.Michel, A.Maignan,M.Hervieu, B.Raveau, J. Mat. Chem.(2005), 15, 386-393

The guest cations : 

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

Overview : 

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

SrMn3O6: 8-shaped tunnels : 

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

SrMn3O6 : 

JSSC, 177 (2004) 3383 [001] SrMn3O6

Slide 21: 

q= 0.52a* + 0.28c* JSSC, 177 (2004) 3383 2000 0010 0001 0002 0003 2011 2010 SrMn3O6

Slide 22: 

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

Slide 23: 

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=2CaMn2O4literature CaMnmO2m m=3 CaMn3O6 this work m=4 CaMn4O8 literature CaMn4O8 CaMn3O6

Slide 24: 

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

Slide 25: 

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

Slide 26: 

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

Slide 27: 

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

The compositionally modulated structure approach : 

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

Slide 29: 

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

The compositionally modulated structure approach : 

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

Slide 31: 

q= 0.52a* + 0.28c* q= 0.54a* + 0.29c* q= 0.66a* + 0.33c* q= 0.52a* + 0.31c* SrMn3O6

Slide 32: 

q= 0.66a* + 0.33c* CaMn3O6: SrMn3O6: q= 0.66a* + 0.33c* SrMn3O6 versus CaMn3O6

Slide 33: 

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

The composite structure approach : 

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

Composite structure Ba6Mn24O48 : 

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

The composite structure approach : 

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

The composite structure approach : 

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 7 8 γ

The composite structure approach : 

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

The composite structure approach : 

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

Slide 40: 

[SrF0.82(OH)0.18]2.5[Mn6O12]

Slide 41: 

[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*

Slide 42: 

[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

Slide 43: 

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]

The composite structure approach : 

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

The composite structure approach: : 

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

The composite structure approach: : 

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

Conclusions : 

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

Conclusions : 

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