Zeitschrift fUr Kristallographie, Bd. 127, S. 173-187 (1968)

By NOBUKAzuNuZEKI and MASATADA WACHI*

The Electrical Communication Laboratory, NipponTelegraph and Telephone Public Corporation, Musasino-si, Tokyo

(Received January 22, 1968)

Auszug

Aus Schmelzen von der Zusammensetzung Bh03' 2M203, M = Mn, AI, Fe,mit einem Uberschu13 von Bi203 als Flu13mittel wurden Kristalle von BhAI40g,Bi2Fe40g und Bi2Mn40l0 gewonnen; ihre Strukturen wurden bestimmt. AlleKristalle gehoren zur Raumgruppe Pbam. Die Gitterkonstanten sind fiir

Bi2Al40g :Bi2Fe40g:Bi2Mn401o:

a = 7,712A, b = 8,112A, c = 5,708 Aa = 7,905 A, b = 8,428 A, c = 6,005 Aa = 7,540 A, b = 8,534 A, c = 5,766.A.

Die Elementarzelle enthalt zwei Formeleinheiten. Die Struktur wurde durchDeutung von Patterson-Schnitten fUr z = 0, t und ! bestimmt und aus drei-

dimensionalen Intensitatsdaten nach der Ausgleichsmethode verfeinert bis zuR-Werten von 0,11, 0,12 und 0,10 fUr die Mn-, AI- bzw. Fe-Verbindung.

BhAl40g und Bi2Fe40g haben die gleiche Struktur. Al und Fe werden vomSauerstoff zum Teil oktaedrisch, zum anderen tetraedrisch umgeben. In denKristallen von BhMn40lO ist die oktaedrische Umgebung durch eine tetragonal-pyramidale ersetzt. Bi hat drei naehste Sauerstoff-Nachbarn mit fast senkrechtauf einanderstehenden (Bi-O)-Richtungcn und au13erdem flinf entferntere.

Abstract

The crystal structures of Bi2Mn40lO (BiMn205), Bi2AI40g, and Bi2Fe40g havebeen analyzed. Single crystals of these compounds were grown from the melt ofthe composition Bi203' 2M203 (M = Mn,AI,Fe) with excess Bi203 added as a

flux. These crystals are all orthorhombic, and their unit-cell dimensions arc:

Bi2Mn40l0 :Bi2AI40g:Bi2Fe40g:

a = 7.540 A, b = 8.534 A, c = 5.766 Aa = 7.712A, b = 8.112A, c = 5.708Aa = 7.905 A, b = 8.428 A, c = 6.005 A.

* Present address: Department of Chemistry ,Tokyo University, Bunkyo-ku,Tokyo , Japan.

174 NOBUKAZU NnzEKI and MASATADA W ACHI

These unit cells contain two formula units. Space groups are all Pbarn. Three-dimensional intensity data was collected by multiple-film integrating vVeissen-berg photography. The structures were analyzed by interpretation of Pattersonsections at z = 0, t, and ;j;, and refined by the least-squares method. The absorp-tion and dispersion corrections were included in data processing. The finalR value are 0.11, 0.12, and 0.10 for Mn, AI, and Fe compound respectively.

Two compounds Bi2Al409 and Bi2Fe409 are isostructural. One kind of AI(Fe)is octahedrally coordinated by six oxygen atoms, and the other kind tetrahedrallyby four oxygen atoms. The structure of the Mn compound differs from the other

two only in that one oxygen atom located at Oot in the others is replaced by twooxygen atoms at 0,0, ::J::0.281, and as the result, Mn(2) is coordinated by fiveoxygen atoms in a square-pyramidal configuration. The coordination of oxygen

atoms around Bi is similar to that of sulfur in sulfosalts containing Bi; there arethree short Bi-O bonds mutually orthogonal, and five morc longer bonds.

Introduction

In the course of systematic studies on the ceramic specimens ofthe oxide systems Bi203-Mn203, Bi203-Ab03, and Bb03-Fe203,three new compounds were found. These compounds were identifiedby the x-ray powder-diffraction patterns of the ceramics obtainedby firing the starting materials mixed in the composition Bb03' 2M203,where M stands for Mn, AI, and Fe. Preliminary study on the systemBb03-Fe203 was reported by KOIZUMI, NnzEKI, and IKEDAl. Thesecompounds were briefly described by LEVIN and ROTH 2 as

Bb03' 2Mn203, Bi203. 2Ab03, and Bb03 . 2Fe203. A short accountof the structure analysis of these compounds was reported by TUTOVet al.3, in which the Mn compound was identified as Bi203. 2Mn203.4.Complete description of these structures has not been presented.

Preliminary crystallographic studies

Powder-diffraction patterns of the three compounds obtainedwith CuKcx radiation are schematically shown in Fig. 1. These patternscould be indexed on the basis of the orthorhombic unit cells, dimen-

1 H. KOIZUMI, N. NnzEKI and T. IKEDA, An x-ray study on Bi203-Fc203

system. Jap. J. Appl. Physics 3 (1964) 495-496.2 E. M. LEVIN and R. S. ROTH, Polymorphism of bismuth sesquioxide. II.

Effect of oxide addittions on the polymorphism of Bi203. J. Res. NBS 68A(1964) 197-206.

3 A. G. TUTOV, 1. E. MYL'NIKOVA, N. N. PARFENOVA, V. A. BOKOV and

S. A. KIZHAEV, New compounds in the system Bi203-Me203(Fe+3, AI+3, Ga+3,Mn+3). Soviet Physics-Solid States 6 (1964) 963-964.

sions of which are listed in Table 1, and the assigned indices areindicated in Fig.1. Similarities in the diffraction patterns ofBi203 . 2 Ab03, and Bi203 . 2 Fe203 are clearly observed, and can be

eXplained if these two are isostructural since the unit cell of thelatter is uniformly larger than that of the former due to the largerionic size of Fe+3 than AI+3. Dissimilarity of the pattern of Mn com-pound to the other two is also apparent in Fig. 1, and the difference

c;:c)'

1

U~ffiDw~~~~n~3~n~~~~~-'-2()

Fig.1. Graphical representation of x-ray powder-diffraction patterns ofBi2Mn40lO, Bi2A1409, and Bi2Fe409. Patterns were obtained by diffractometer

with CuKIX radiation

suggests that the structural scheme of the compounds is somewhatdifferent from that of the Al and Fe compound. The unit cell of theMn compound is found to be similar to that of HoMn205 describedby QUEZEL-AMBRUNAZet al.4. The reported lattice constants of thelast compound are a = 7.36, b = 8.49, and c = 5.69 A.

Single crystals of the three compounds were all grown by theflux method. Mixture of oxides, Bi203 + 2M203, were melted withexcess amount of Bi203 in Pt crucible at the temperature above

4 S. QUEzEL-AMBRuNAz, F. BERTAUT and G. BUISSON, Structure des com-

poses d'oxyde de terres rares et de manganese de formule TMn205. Compt. rend.Acad. Sei. [Paris] 258 (1964) 3025-3027.

!Bi2Mn401O

I

Bi2Al40g Bi2Fe4OgIColor black colorless light tanLuster submetallic transparent transparentHabit prismatic thin tabular to thin tabular to

(octagonal) square pnsm square prismForms {100} {010} {110} {ltO} {110} {1I0}

{110} {1I0} {OO1} {001}{001}

-~-~-

Lattice a 7.540 A :!:: 0.005 A 7.712A:!:: 0.005A 7.950A:!:: 0.005Aconstants b 8.534 8.112 8.428

c 5.766 5.708I

6.005

Space group D§~ ~Pbam PbamI

Pbam

Cell content 2 2 2

Sampledimension,R 0.0008 cm 0.0020 em 0.0016 em

Absorptionfactors

p 1474 em-1 987 cm-1 1406 cm-1pR 1.18 1.97 2.25

Densitymeasured 7.133 :!:: 0.005calculated 6.979 (Bi2Mn4Og) 7.121 (Bi2Mn4OlO)

176 N OBUKAZU NnzEKI and MASATADA W ACRI

9000 C for 12 hours. Cooling of the melt was carried out at a rate ofabout 7°C per hour to 800°C, and the power to the furnace wasturned off. The synthesized crystals were extracted from the solidifiedmass by immersing the entire crucible in a hot nitric acid. Dimensionsof the obtained crystals were up to 0.5 X 0.3 X 0.3 mm. The color,luster, habit, and crystal forms of the three kinds of crystal aresummarized in Table 1.

Lattice constants and space group of the three compounds arealso listed in Table 1. The lattice constants were determined fromprecession and Weissenberg photographs, and space group from theobserved systematic extinctions; hOl reflections with h odd, andOkl reflections with k odd are missing. These unit cells contain twoformula units. A test for piezoelectricity gave a negative result andthus a centrosymmetric group Pbam was uniquely assigned.

To determine the number of oxygen atoms in the chemical formulaof Mn compound, density measurement with a pycnometer wascarried out on the single crystals. The measured value was comparedwith calculated values assuming two formulae, Bi2Mn40g (Bi203.2Mn203) and Bi2Mn401O (BiMn205), as shown in Table 1. A goodagreement with the latter established the correct formula of thecompound. It is to be noted that if the compound is a stoichiometricone, two kinds of valency, i. e. trivalent and tetravalent valencieshave to be assigned to manganese ions. The correct formula is tobe expressed as Bi2Mn2+3Mn2+401O.

Structure analysis

Intensity data of all the three kinds of crystal were collected byequi-inclination integrating 'Veissenberg camera with multiple-filmtechnique, and c-axis photographs were taken with CuKex radiationup to the third level for Mn and Al compound, and the second levelfor Fe compound. Intensities were measured by visual comparisonwith a standard intensity scale. Absorption corrections were per-formed assuming cylindrical shapes with radii obtained by averagingthe lengths in the square cross sections of the prismatic crystals.The radii of cylinders and the absorption factors of the crystals usedin the experiments are summarized in Table 1. For the correctionof the higher-level reflections BUERGER and NUZEKI'S method 5 wasused. Intensities were then corrected for the usual Lorentz andpolarization factors, and F~bs(hkl) values were placed on an absolutebasis by WILSON'S method.

The structure analyses of the three crystals were all carried outby the following procedure.

Since the lengths of c axes are about 6 A, and there exist mirrorplanes parallel to (001) at z = 0 and 1/2 in space group Pbam, it wasdeduced that all atoms in the unit cell are to be located at z = 0,1/2, or nearly 1/4. Thus the three-dimensional Patterson sections atthe above z values were synthesized. The atomic coordinates of Biand other lighter metals were easily determined from the sections.Locations of oxygen atoms were successively made clear after a fewtrials of (FObs- F metal) difference Fourier syntheses.

It was confirmed at this stage that the structures of BhAl40g andBhFe40g are essentially identical, and that the structure of BhMn40g

5 M. J. BUERGER and N. NnzEKI, Correction for absorption for rod shapedsingle crystal. Amer. Mineral. 43 (1958) 726-728.

Z. Kristallogr. Bd. 127, 1-4 12

178 NOBUKAZU NIIZEKI and MASATADA W ACHI

differs from the above two in one aspect. In the former two structures,

one oxygen atom was found at x = 0, y = 0, z = 1/2, i.e. at equipoint2 b of Pbam, while in the latter structure oxygen atoms at the same

x and y coordinates were found in sections at z = 1/4 and 3/4, i.e. at

Table 2. Final atomic parameters of Bi2Mn4010, Bi2Al409 and Bi2Fe409

Bi2Mn401O Bi2Al409 Bi2Fe409

Bi x 0.1597 ::I::0.0003 0.1704 ::I::0.0004 0.1761 ::I::0.0006

Y 0.1643 0.0003 0.1668 0.0003 0.1715 0.0005z 0 0 0B 0.58 0.04 0.49 0.05 1.12 0.08

M(1)* x 1/2 1/2 1/2

Y 0 0 0z 0.262 ::I::0.003 0.257 ::I::0.005 0.257 ::I::0.008B 0.58 0.1 0.7 0.4 1.15 0.37

M(2) x 0.407 ::I::0.001 0.347 ::I::0.003 0.351 ::I::0.002

Y 0.354 0.001 0.339 0.003 0.334 0.002z 1/2 1/2 1/2B 0.65 0.1 0.8 0.4 1.25 0.32

0(1) x 0 0 0y 0 0 0z 0.281 ::I::0.01 1/2 1/2B 0.8 1.0 1.5

0(2) x 0.386 ::I::0.004 0.380 ::I::0.006 0.373 ::I::0.007

Y 0.176 0.004 0.201 0.005 0.198 0.006z 0.250 0.008 0.251 0.007 0.243 0.014B 0.6 1.1 1.0

0(3) x 0.147 ::I::0.006 0.140 ::I::0.007 0.137 ::I::0.010

Y 0.418 0.005 0.433 0.007 0.418 0.010

z 1/2 1/2 1/2B 0.6 1.0 1.2

0(4) x 0.147 ::I::0.006 0.143 ::I::0.008 0.143 ::I::0.010

Y 0.425 0.005 0.426 0.007 0.415 0.010z 0 0 0B 0.6 1.1 1.6

R** 0.11 0.12 0.10

*M Mn, Al or Fe.

** R Reliability factor defined as .E IIFobsI- IF calc II.ElFobsl

equipoint 4e. Since the number and coordinates of the other oxygenatoms were same for the two types of the structure, it was proved thatthe number of oxygen atoms III the formula IS 9 for the Al and Fecompounds, and 10 for Mn compound.

The obtained structures were then refined by the three-dimensionalleast-squares method. At this stage the effect due to the anomalousdispersion was corrected. Three to five cycles of refinement withdiagonal approximation and without a special weighting system wereperformed by the computer NEAC 2206 of the laboratory. Thenumbers of reflections used in the refinements are 308, 266 and 248for Mn, AI, and Fe compound respectively.

The final atomic coordinates and temperature factors are tabulatedin Table 2 for the three crystals. The final values of Rare 0.11, 0.12

h k 1 IF, I F,

10 1718} -17/j

185 19928 3610 19

115 -I}1i

1"1 -I""196 20329

_)0

5 1622 6

165 _162

78 - 7556 -

56131 -15l.112la 135

23 27156 162157 165

5 - 5

9"-113

"9la8

55 -58

191 _22143 - 39

173 17828 3366 - 7123 16

113 -12118

-25

86 9079 -118

20""20}

109 11528 31

1J5 171t16} -179

19 -11

87 8646 4851 6010 - 696 92

116 -132132 -157

10 1222

_ 1029 }O

137 136277 296

21 - 16

5 J39 - "I71 - 7622 - 15

132 14628 33

9 1272 75

115 -101H5 -153

200,681102J,56789o 2 012J,567891 J 02J,56789o , 012J.567891502J,5678o 6 0I2J.56781702J

Table 3. Observed and calculated structure factors of Bi,JIn,O"

h k 1 IF,I F

105 10541 - 41

21 1',21 '2739 - 30

92 -11683 8121 8

10" 8')131 1}2

1.7 - 29131. -109

19 13111 107

15 22

"2 -51,

58 -60

98 8967 57

201 199181 -156l}O -109186 2111

28 - 281J6 36

226 -265138 -115129 112

596":.13 52

63 75105 - 95

53 - 68128 -121277

-2""66 51113 - 90

51 49171 155

95 - 975r. - 6519 825 - 1983 - 8023 - 3:1

215 21520 - 1098 -10010 7

134 -1}110 7

115 12786

- 76212 184

73 6552 5137 31

133 -HO99 -12070 7016 957 58

'70567o 8 012J

"561 9 02J,,o 10 0I20012,681112J,5678902112;,567891 J 12J,567890',12J,5678151

h k 1 IF,I F,

203 21684 - 85'Jr. - 9323 1953 - 4746 I,}

77 821119 156

}O 33107 - 99

12 3397 - 91to - 7

192 1}815 - 1023 20

145 -13575 -

8691 9')62 5835 3069 6885 - 91

1)1 -14022 1751 - 4740

"7126 10951 - 4073 -

6r.35 - 42

162 13115 -

81.9

_ r.665 - ')')96 8348 41

o 6240 245203 -183261 -2'12105 986y

- 69162 1')0250 -195

58 - 56188 170

37 33r.5 1.861 63

103 -1'10I', - 19

172 -1771113 -101

60 - 113u1 6235 - 25

IllS tlt2111 -116tit'} -127

17 - 111'Il) - 53

2. 5 1J,56780611

,671 7 I

567o 8 112

~1 9 1

J,5o 10 11

"Jo 0 22

"681 1 2.

89o 2. 21

h k 1

132.

0'12

,,56781 5 22

78o

(,2

12J,5671722

Ro 8 2.1230,5

"19223,o 10 21

00 J

"r,811

31117'

"21

"127RJ

11929

13(,

9564

119392088

124161

10129

10157

217613

11')126

66130

J2Zit

111121.

55

17139

9'1611,8

1612J

1518811

18,

'}O76

18'11529

18010J

95

F

-155

- 62HO

"39

- 68- 29-25Y

140- '7- 17

"3-1'51-101

109

- 23114108

- 71-1/,)

"- 21

"126126

-115- 16-14/,

- 237015

I2J-12'1-

76

"-"J'- 8'-109-

0,8

- 17125

-102- 61

J615527

-142

"-14188

- 97- 7J

201t-14

"-214-103

98

h k 1

516

1t2 4942 4653 6386 -8660 - 69

176 -19581 6885 - 73711 63

125 13664 - 70')3 - 601/j 2081

- 7519

- 2')162 t8t

10-

877 - 9010 b

1.2:; -1225 6

3" -45

173 15580 7649 4242 47

127 -12493 - 9363 6420 19

"3ItS

156 18668 - 8073 - 8321 1245 - 1t337 36

159 15632 2960

- 6932 2962 - 69

5 - 7171 155

10 15155 -120

91 -81

yo 86'18 4929 2882 - 66

131 -12533 28

'6 -42

55 5389 9957 -

6237 - 37

110 11630 - 40

8o 2 31

,6781

J'

5678

0'J

1

3

"7815 J

3

"5

"70631

173

~o 8 J1

,1 Y 3

3o 10 3

12*

180

h k 1

2 0 0468110234,67,9o 2 01234,67,91 3 0234,6789o 4 01234,67891 , 0234,678o 6 01234,671 7 02

100122199.,o

111102",4952o

907'124

14'110

03

10'104

67116

""13'61216

o

"121

'9o112100

19'100o

10'159

7'109632127

114143

'"60

"1260

2121579

o63o

'"o'2103

NOBUKAZU NnzEKI and MASATADA WACHI

Table 4. Observed and calculated structure factors of Bi,AI,O,

Fo

-121-lit?

2'1-55

11-11t5-12817'

55-45

7- 93- '7-117-173

11819

103

10'- 62-1216,

39-151-5822'

6-153

24-BB- ,

134- 9220'10915

"-litO-7310'6,

- 1626

10'-128-126

46371868

241-12- 77- 11-53

6176

654

-1 OJ..

h k 1

3 7 0

'.,67o 8 01234,6190234o 10 012001246811123.,6789o 2 11234,6781 3 123.,6789o 4 11234,678

IFoi

'"1231720J6

"100802,7276'096o

12811

'910'156

238111777

12796

"18199

15949oo

10353

'"198'7o26

16191

13447

118o

211o

153o

'0o100108175

'9o21

1709{}

138

'0

F

-135117

20-28

JJ_ 88-101,

69177381

- 55- 90

3131,

_ 8

- 518'.55

038-150- 80161

-107.,_228-114197

54-13

17-115_

62

-137-233

527

2916,

-87

-HI.,-lOB-

,188,

-1181

-422

116-110

196

4'_ 824

-146- 7613142

h k 1

9411512,4567806112,45671 7 12,'.567o B 112,.561912,4o 10 112o 0 224681 1 22,.56789o 2 21234567

and 0.10 for BhMn40lO, BizA140g,comparison between the observedare listed in Tables 3, 4 and 5.

10J9

17310917'

62o

23

9'159o

112o

7210

138o

22,,681

152

"o1282

127

"o35

10162

"o

"'o539728

28117212'.1448,88

18168

15279

o

'975.,139"5'957

o80

105111

- 16

175- 96-159

'.892{}

99162

1

- 981

-60.

1271

'0-137- 71

131

"1-13

"- 79-1}6

37,2,

109_ 6ft-

6,- 2

1201

-55105

27279

-182-133

19'-110

105-206- 71

15'92

- 850

- 8,- '9-107-121.1

4''5

- 98'-110

-128

h k 1

8 2 29

"2

2,.56789011212

56781 ') 2

,678o 6 212,'.5671 7 223.,6o 8 212,.,1 9 22,4o 0 32.681 1 323

16

"1116o2<)1

o74

o6'.o

118115180

'.82852

11311'111817

10910::;

1"12977.,7253

136o

122o

10'o121

o

7'11267

122691298

1042'.o2073

"26136,2251376B

1279326

194119

Fo

'.6"-115_ .

2969

- 71,- '7- 811,2

-165150

"- 24

'.1-112-107

12}

25

"'102- 96-120

60556266

16715

-120

"- 8,- 9136-11

7'-115-73

11067

-15-99-111

J15

20

8'-4903

"2- 5198

-114--66

,"-9'J4-185-100

h k 1

"3

567.o 2 31

81 3 3

}.678043123.5678

",

23.567o 6 3123.,61 7 32,4,o8 ,1

17353oo

96116179

79o

'0156.7

12453

117o

193o

137o

'.7o

87170

59o

23Ilt2

82131

4431

171122154

54o

17

'" o9\o6,o

12621

15078

132,6

.7911542o

3361

Fo

169.,

- 1213

-104-104-189

'0631

"3-,"-126

"- 9'- 3161

2-108

1

-"- 2

- 8816B'5

- 726

-130- 6,119

"JJ153

- BB-11t1

'0916

"9 1-B\- 0

- 51- 11192,

-122- 6B

118J5

- 69-122

J64

"_

60

and BizFe40g respectively. Theand computed structure factors

Discussion of the structures

The interatomic distances between the neighboring atoms aretabulated in Table 6, which is classified according to the kind of themetal-oxygen coordination polyhedron. These polyhedra are graphi-cally shown in Fig. 2. The distances are also shown in the schematicrepresentation of the structures, Figs.3, 4 and 5. In Figs. 6 and 7, thethree-dimensional structural schemes of BizMn4010 and BizA140g arerespectively illustrated.

A significant difference between the two structures illustrated inFigs. 6 and 7 is found only In the coordination of oxygen atoms

The crystal structures of Bi~n4010, Bi~409 and Bi2Fe4Og 181

Table 5. Observed and calculated structure factors of Bi,Fe,O,

b k 11'.1

F, b k 1 IF.I F, h k I IF.I F, h k 1 IF,I F, h k I IF.t F,

2 0 0 107 -109 9 5 0 74 _ 86 2 2 1 74 60 7 7 1 8 - 9 o 't 2 181 -190, 107 -112 o 6 0 271 213 3 17 15 o 8 1 98 - 90 1 138 1326 270 272 1 51 -52

,1 1 103 -11} 2 8 10

8 59 -"2 B3 - 63 5 177 152

"50 3 59 - 50

1 1 0'"

-32 3 8 - 8 6 98 -77 3 8 8 , 17 162 12J -105 ,

21 -21 7 118 -132, 8 11 5 80 - 69

3 175 -171t 5" "

8 63 61 5 77 78 6 107 -10), 172 162 6 169 113 9 33 30 6 77 - 6, 7 139 1165

"3' 7 17 -17 131 82 -76 1 9 1

'0 - 39 8 0 26 98 -88 8 50 - 57 2 17 18 2

3'28 9 70 _ 60

7 25 -27 1 7 0 17 17 3 1" 150 3 78 83 1') 2 169 1588

"- It2 2 90 .. 69 , 17 -18 ,

"- J1 2 53

"9 80 -81 3 102 -116 5 137 -136 5 60 - 72 3 132 -112o 2 0 136 -121

, 109 109 6 , 6 o 10 1 0 - 10 , 107 -971 135 -135 5 13 -11 7 17"

1 91 110 3 121 952 199 187 6 65 - 63 8 8 6 , 3 6 74 573 59

"7 8 10 9 78 77 3 13 - 12 7 78 71,

13' "0 o 8 0 93 -98 0'1 68 - 65 o 0 2 287 278 8 21 235 55 35 1 68 -71 1

"5 231 2 219 -2}8 o . 2 126"76 55 - 55 2

9'103 2 30 30 '. 11tS -155 1 25

-20

7 108 -111 3 25

"3 22

- 19 . 169 160 2 H2 -1'i58 90 85 , 78 83 '. 8 - 7 8 1113 -128 3 17 159 76 70 5 3'. 38 5 t/,8 -I',) 1 1 2 118

"8 '.s; -s;

1302" -196 6 62 - 56 6 51 - '5 171 -I?} 5 13 11

2

" -"1 9 0 93 -101 7 130 133 1,6

- 't) . 108 1033 216 203 2 34 J1 8 38 38 l't9 1'jJ 7 38 - 28, 1J - 9 3 118 115 9 '2 - 32 i 10'

12(} 8 87 -1045 187 -190

, 38 - 35 151"

37 54-"

1 7 2 71 726 29 33 5

"'- 90 2 186 165 7 51

"2 10} -85

7 79 -71 o to 0 13 12 3 126 - 99 8 '12 -"3 21 - 20

8 ,- 3 1 67 13 '. 139 -149 9 25 - 22 '. 126 1",9 75 91 2 38 '., 5 76 71 o 2 2 193 -18'1 5 61 60

o , 0

"- 57 3 33 - 27 6 17 20 1 06 -87 6

"-%91 202 193 , 17 2'. 7 '. - 5 :)1.

2' 7 42"

2'"

134 ,0 0 1 186 190 8 59 67 3 94 74 n 8 2 1')2 -1353 21 - 20 2 153 -151.,. o . I 110 t2J, '. 0 - 3 I 81 -78, 115 105 ,

25-

2} 1 37 -}2 5 29 33 2

"33

5 105 -10} 6 138 123 2 1011- 95 6 1/11 -130 3 17 13

63' -33 8 107 _126 3 8 6 7 116 -11}

" '.,

7 100 108 111 25 2/, '. 17 -18 8 51 ',:1 3 '.91,6

85'

63 2 236 -255 5 17 19 9 97 76 6 10' -979 58 -%9 3 72-

87 6 97 90 1 J 2 lJ9- 85 1 9 2 3'. -351 5 0 25 22 , 245 218 7 28 - 23 2 '. 6 51 50

2 79 67 5 61 62 8 82 -93 JoG 3311 3 1351"3 193 -188 6 37 - '0 1 7 1 0 3 13 - 11 , 3H - 35, 98 -10} 7 13 -13

,"2 -151 eo - 6:; o 10 2 '., - 56

5 55

"8 90 - 90 3 25 -27 10 10 1 80 69

6 55 61 9 112 - liO I. 135'"

15 - 18 10 - 77 4 -

, 021 1115 -128 25 25"

- 28 25

"1 253 -2)7 2') - 26 I:..!) 1 ~II

Table 6. Bond lengths and bond angels in Bi2Mn40lO, Bi2A1409 and BbFe40g

(i) Octahedral M-O coordinations

I

Bi2Mn401O Bi2Al4Og Bi2Fe4Og

I

notation(Fig.7a)

M-0(2) 1.83 A 1.84 A 1.95 A aM-0(3) 1.90 1.93 1.95 bM-0(4) 1.98 1.87 2.05 c

0(2)-0(3) 2.64 2.69 2.82 d0(2)-0(3') 2.57 2.60 2.79 e0(2)-0(4) 2.59 2.69 2.80 f0(2)-0(4') 2.59 2.66 2.76 g

0(3)-0(3') 2.62 2.42 2.58 h0(3)-0(4) 2.88 2.86 3.01 j

0(4)-0(4') 2.56 2.51 2.69 k

0(3)-M-0(4) 96.10 98.4 0 97.4 0 IX

0(4)-M-0(4') 80.5 84.2 82.1 f30(2)-M-0(3) 93.4 92.6 92.7 y

0(2)-M-0(4) 88.4 91.3 91.0 t50(2)-M-0(3') 89.9 90.0 88.8 e

o (2)-M-0 (4') 88.1 91.9 87.4

Bi2Mn401Onotation(Fig.7b)

1.91 A a 0(1)-Mn-0(1')2.10 b 0(2)-Mn-0(2')2.04 c 0(3)-Mn-0(1)

0(3)-Mn-0(2)3.03 d 0(1)-Mn-0(2)3.10 e2.90 f2.53 g

2.88 h

(iii) Tetrahedral AI-O and Fe-O coordinations

Bi2Al4Og

I

Bi2Fe4OgNotation

(Fig. 7 c)

M-0(2) 1.83 AI

1.93 A aM-0(2') 1.83 I 1.93 bM-0(1) 1. 76 1.83 cM-0(3) 1.77 1.84 d

0(1)-0(3) 2.83 2.97 e0(2)-0(2') 2.85 3.08 f0(3)-0(2) 2.96 3.14 g

0(1)-0(2) 3.00 3.06 h

0(2)-M-0(2') 102.30 106.1 0 IX

0(3)-M-0(1) 106.6 107.6 fJ

0(2)-M-0(3) 113.0 108.2 Y0(2)-M-0(1) 111.1 113.3 15

Bi2Mn401O BhAl40g Bi2Fe40g Notation(Fig. 7 d)

Bi-0(2) 2.07 A 2.11 A 2.23A aBi-0(4) 2.15(2x) 2.18 (2 X) 2.23 (2 X) b

0(2)-Bi-0(4) 85.30 82.10 86.70 IX

0(4)-Bi-0(4') 89.2 86.7 89.3 fJ

182 N OBUKAZU N IIZEKI and MASATADA W ACHI

Table 6. (Continued)

(ii) Square-pyramidal Mn-O coordination

82.90

86.797.0

100.492.6

Mn-0(1)Mn-0(2)Mn-0(3)

0(3)-0(1)0(3)-0(2)0(1)-0(2)0(1)-0(1')0(2)-0(2')

(iv) Bi-O coordination (three shortest bonds)

di ej9

h f+ - e

around M(2) ions, which is indicated in the figures by black coloringof spheres. In Bi2Al409 and BbFe409 structures (Fig. 7) the coordina-tion is tetrahedral, while in BbMn40lO structure (Fig.6) it is squarepyramidal. The position of Mn(2) ion is slightly (about 0.03 A) shiftedtoward the apex of pyramid from the center of the square base.Since three oxygen atoms surrounding M(2) ion, i. e. 0(3) and two0(2)'s are located in approximately identical geometry in both struc-tures, the difference is due to whether another oxygen atom, 0(1),is at equipoint 2b or at 4e. The bond lengths and bond angles foundin these coordination polyhedra are tabulated in groups (ii) and (iii)of Table 6. If the sixth neighboring oxygen atom is sought, it islocated at 2.94 A from the Mn(2). This weak bond is indicated bydotted line in Fig. 2.

Manganese in the various oxide structures, MnO, Mn203, and Mn02is known to have octahedral coordination, although in Mn304, which

or]') 00(7)

b) c)

Fig. 2. Coordination polyhedra and bond systemsfound in the structures of BhMn40lO, Bi2A1409, andBi2Fe409; (a) octahedral, (b) square-pyramidal, (c) tetra-hedral, and (d) Bi-O coordinations. Roman letters ac-companying the straight lines indicate the kind of bond,and their lengths are listed in Table 6. Greek lettersindicate the bond angles, and their values are also listedin Table 6. Large circles represent oxygen, small circles

metal, and cross-hatched circles bismuth atoms

8;

d)

184 N OBUKAZU N IIZEKI and MASATADA W ACHI

has a distorted spinel structure, one kind of Mn is coordinated byfour oxygen atoms arranged in the shape of square instead of tetra-hedral arrangement in regular spinel. Nature of the square bondwas discussed by SINHA and SINHA6 as the result of hybrid orbitals.The square-pyramidal coordination found in the present study wasalso reported in HoMnz054, the structure of which is same as BiMnz05except the difference found in the coordination around Ho and BiIOns as discussed below. The coordination of oxygen atoms in the

b

Fig.3. Schematic representation of the structure of BhMn40lO. The structure isrepresented in the full unit cell of the projection on (001). The open circlesindicate the atoms at z = 0 or 1/2, and the shaded circles those at nearly 1/4 or 3/4.

The chemical bonds between the neighboring atoms are shown by straight linesfor the nearest, by dashed lines for the second. and the third.nearest neighbors.Dotted line is used to indicate the weaker Mn-O bond. The figures accompanying

these bonds are interatomic distances in A

same square-pyramidal shape around the central V ion is reported ina few structures, VZ057, K3V50148 and SrVSiz07 (mineral haradaite)9.

6 K. P. SINHA and A. P. B. SINHA, Valency distribution and bonding in

some oxides of spinel structure. J. Physic. Chern. 61 (1957) 758-761.7 H. G. BACHMANN, F. R. AHMED and W. H. BARNES, The crystal structure

of vanadium pentoxide. Z. Kristallogr. 115 (1961) 110-113.8 A. M. BYSTROM and T. E. EVANS, The crystal structure ofK3V5014. Acta

Chim. Scand. 13 (1959) 377-378.9 Y. TAKEUCHI and W. JOSWIG, The structure of haradaite and a note on the

Si-O bond length in silicates. Mineral. Journal 5 (1967) 98-123.

The coordination polyhedra of Mn( 1)-0 as well as of Fe( 1)-0 andAI(l)-O are all octahedra, bond lengths and bond angles of whichare tabulated as group (i) of Table 6.

The bond lengths and bond angles associated with Bi-O coor-dination are tabulated in group (iv) of Table 6 for the shortest three

b

o 7},

Fig. 4. Schematic representation of the structure of Bi2AI40g. Explanations forsymbols and figures are same as in Fig. 2

Fig.5. Schematic representation of the structure of BhFe40g. Explanations forsymbols and figures are same as in Fig. 2

186 NOBUKAZU NnzEKI and MASATADA WACHI

bonds. The longer interatomic distances are indicated in Figs. 3, 4 and 5.The Bi-O bonds in the three structures presently discussed are alldistinctly directional. This is in contrast to the Ho-O bonds in

Fig. 6. Structural sheme of BhMn4010. Large circles represent oxygen, smallcircles managnese, and cross-hatched circles bismuth atoms. A square-pyramidal

coordination is indicated by black coloring of related atoms

Fig. 7. Structural scheme of Bi2A140g, and Bi2Fe40g. Large circles representoxygen, small circles aluminum or iron, and cross-hatched circles bismuth

atoms. A tetrahedral coordination is indicated by black coloring of related atoms

HoMn2054, in which Ho is located at the center of a trigonal prismformed by six oxygen atoms. The three shortest bonds shown inFig. 2d are nearly orthogonal to each other. If the second- and third-

nearest neighbors are considered Bi ions are surrounded by eightoxygen atoms.

In building up the three-dimensional structures illustrated inFigs. 6 and 7, the isolated BiOa groups are connected along c axessharing oxygen atoms with M(2) ions. Along a and b axes, M(1) ionsplay the role of connecting together these groups. The nature ofcoordination in Bi-O in the present double oxides is similar to theBi-S coordination in sulfosalts structures. If the Bi2Al409-type struc-ture is expressed in terms of the coordination polyhedra, the follow-ing formula is obtained: BhM~etrahedralM~ctahedraI09.Although thecorresponding sulfosalts is not known to occur in nature, it may beworth-while to synthesize and to study the structure of such a com-pound as CuFeBiSa, which satisfies the above condition for thecoordination.

Acknowledgement

The authors are grateful for S. FU8HIMI of the laboratory whosynthesized the single crystals used in the present studies.