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Electron microscopic study of the system MnS-Er2S3
Journal
of the Less-Common
ELECTRON
Metals,
MICROSCOPIC
J. ARCE de la PLAZA
110
STUDY OF THE SYSTEM MnS-Er,S,*
and L. C. OTERO-DIAZ
Dpto. Q. Inorgcinica, F. Quimicas, Uniuersidad Complutense, Q. Inorgcinica Elhliyar, C.S.I.C. 28006 Madrid (Spain)
(Received
December
371
(1985) 371 - 374
28040
Madrid
and Instituto
18, 1984)
Summary A systematic search, using X-ray diffraction and HRTEM techniques, was performed to elucidate the phases present in the Mn-Er-S ternary system at 1373 K. Four related crystallographic phases have been found; two of the parameters are constant, whilst the third changes.
Materials and experimental
methods
The binary sulphides o-MnS (Bl-type) and Er$, (&Ln,Ss type) were prepared by induction heating a carbon crucible containing the oxides under an Ar + H2S gas stream at 1473 K and 1773 K. Mixtures of MnS/Er& in ratios 5:1, 5:3, l:l, 4:5, 3:4, 2:3, 3:5 and 1:2 were heated at 1373 K for 24 days in alumina crucibles within evacuated silica tubes. The powder products were studied by X-ray diffraction, using an XDC 700 Guinier-Hagg focusing camera, and a D 500 Siemens diffractometer, and by HRTEM using a Siemens Elmiskop 102 and a JEOL 200 CX electron microscope.
Results and discussion The X-ray powder patterns were extremely complex with more than 100 reflexions in the range 5” < 28 < 90”) suggesting the presence of several phases in each sample. This was confirmed and clarified by electron microscope observations: (i) Small concentrations of Er& can be incorporated into the MnS matrix by the formation of isolated (113) twin planes; subsequent clustering of these extended defects give rise to lamellar twinned regions of the orthorhombic MnEr&, phase, as can be seen in Fig. 1.
*Paper presented at the International land, March 4 - 8, 1985.
Rare Earth
0022-5088/85/$3.30
0 Elsevier
Conference,
Sequoia/Printed
ETH Zurich,
Switzer-
in The Netherlands
Fig. 1. Electron micrographs at low magnification and patterns, showing the presence of isolated and clustered matrix.
the corresponding (113) twin planes
diffraction in an MnS
(ii) The existence of MnEr& and monoclinic MnEr$, (Fig. Z(a)) phases, previously reported and based on X-ray powder work [l] was confirmed. (iii) The presence of two new phases: Mn,Er,S1r (orthorhombic, Fig. 2(b)) and MnsErsS,, (monoclinic), which can be regarded as ordered intergrowths of the two previous phases was revealed. (iv) High-resolution images from some crystals showed very complex microstructures due to disordered intergrowths of these phases, Fig. 3, even after a long annealing period (25 days at 1373 K). The structures of these related phases can be described using the crystallographic operation known as “chemical twinning” on the unit cell level [2,3] which has been applied to the isostructural Mn-Y-S [4] and Pb-Bi-S [5,6] systems. According to these principles, the structures are built up of slabs of MnS (Bl) structure joined along the twin planes, indicated by small arrows in Fig. 4, which contain cations in trigonal prismatic coordination. The twin band widths (sequences) for these structures are indicated in Fig. 4.
Fig. 2. MnEr&
High-resolution images and diffraction patterns of well ordered phases. (a) and (b) MnzEr6S,, ; the direction of the incident beam is indicated in each case.
Fig. 3. High-resolution image and diffraction pattern from intergrowth of the two phases indicated in the micrograph.
0,* o
.
one crystal
with a disordered
5 (0.112) Mn.Er(O.ll2)
Mn,%S,,
. . ..(4.4.3f.*..
qMnEr,S,
*..*(4,4)*...
+ MnEr,S,
.“*(4,3)*.”
b
0.. 5 lO.ll2) o,.Mn.EdO.ll2)
Mvr, 3,
. . ..(4.4.4,3)***. =MnEr S
2 4
=2MnEr,S,
. ..*(4.4).... .*.+(4,4)**..*
l
Mn,Er,S,,
..**(4,4,3f*...
MnEr,,S,
. ..*(4.3)**.*
Fig. 4. Structural models of (a) MnzEr eS rr, (b) Mn3ErsSrs (after Hyde et al. [ 2 - 41). Phase - deeI (A) 12.7 A.. (4,4). . 4 x dl,,,, 10.9 B (4,3). . 3x T4 x d{lU) c (4,4,4,3). . 23.7 - d(A) + d(B) 34.7 - d(A) + 2d(B). D..(4,4,3)2..
phases
projected
=
along
[OlO]
374
Acknowledgment One of us (L.C.O.) wish to acknowledge with appreciation discussions with Professor B. G. Hyde, R.S.C., A.N.U., Canberra, and for the use of his electron microscope (JEOL 200 CX).
valuable Australia,
References 1 C. Adolphe, Ann. Chim. (Paris), 10 (1965) 271. 2 S. Andersson and B. G. Hyde, J. Solid State Chem., 9 (1974) 92. 3 B. G. Hyde, S. Andersson, M. Bakker, C. M. Plug and M. O’Keeffe, Prog. Solid State Chem., 12 (1979) 273. 4 M. Bakker and B. G. Hyde, Phitos. Mug. A, 23 (1978) 615. 5 A. Prodan, M. Bakker, M. Versteegh and B. G. Hyde, Phys. Chem. Miner., 8 (1982) 188. 6 D. Colaitis, D. van Dyck and S. Amelinckx, Phys. Status Solidi (AI, 68 (1981) 49.
of the Less-Common
ELECTRON
Metals,
MICROSCOPIC
J. ARCE de la PLAZA
110
STUDY OF THE SYSTEM MnS-Er,S,*
and L. C. OTERO-DIAZ
Dpto. Q. Inorgcinica, F. Quimicas, Uniuersidad Complutense, Q. Inorgcinica Elhliyar, C.S.I.C. 28006 Madrid (Spain)
(Received
December
371
(1985) 371 - 374
28040
Madrid
and Instituto
18, 1984)
Summary A systematic search, using X-ray diffraction and HRTEM techniques, was performed to elucidate the phases present in the Mn-Er-S ternary system at 1373 K. Four related crystallographic phases have been found; two of the parameters are constant, whilst the third changes.
Materials and experimental
methods
The binary sulphides o-MnS (Bl-type) and Er$, (&Ln,Ss type) were prepared by induction heating a carbon crucible containing the oxides under an Ar + H2S gas stream at 1473 K and 1773 K. Mixtures of MnS/Er& in ratios 5:1, 5:3, l:l, 4:5, 3:4, 2:3, 3:5 and 1:2 were heated at 1373 K for 24 days in alumina crucibles within evacuated silica tubes. The powder products were studied by X-ray diffraction, using an XDC 700 Guinier-Hagg focusing camera, and a D 500 Siemens diffractometer, and by HRTEM using a Siemens Elmiskop 102 and a JEOL 200 CX electron microscope.
Results and discussion The X-ray powder patterns were extremely complex with more than 100 reflexions in the range 5” < 28 < 90”) suggesting the presence of several phases in each sample. This was confirmed and clarified by electron microscope observations: (i) Small concentrations of Er& can be incorporated into the MnS matrix by the formation of isolated (113) twin planes; subsequent clustering of these extended defects give rise to lamellar twinned regions of the orthorhombic MnEr&, phase, as can be seen in Fig. 1.
*Paper presented at the International land, March 4 - 8, 1985.
Rare Earth
0022-5088/85/$3.30
0 Elsevier
Conference,
Sequoia/Printed
ETH Zurich,
Switzer-
in The Netherlands
Fig. 1. Electron micrographs at low magnification and patterns, showing the presence of isolated and clustered matrix.
the corresponding (113) twin planes
diffraction in an MnS
(ii) The existence of MnEr& and monoclinic MnEr$, (Fig. Z(a)) phases, previously reported and based on X-ray powder work [l] was confirmed. (iii) The presence of two new phases: Mn,Er,S1r (orthorhombic, Fig. 2(b)) and MnsErsS,, (monoclinic), which can be regarded as ordered intergrowths of the two previous phases was revealed. (iv) High-resolution images from some crystals showed very complex microstructures due to disordered intergrowths of these phases, Fig. 3, even after a long annealing period (25 days at 1373 K). The structures of these related phases can be described using the crystallographic operation known as “chemical twinning” on the unit cell level [2,3] which has been applied to the isostructural Mn-Y-S [4] and Pb-Bi-S [5,6] systems. According to these principles, the structures are built up of slabs of MnS (Bl) structure joined along the twin planes, indicated by small arrows in Fig. 4, which contain cations in trigonal prismatic coordination. The twin band widths (sequences) for these structures are indicated in Fig. 4.
Fig. 2. MnEr&
High-resolution images and diffraction patterns of well ordered phases. (a) and (b) MnzEr6S,, ; the direction of the incident beam is indicated in each case.
Fig. 3. High-resolution image and diffraction pattern from intergrowth of the two phases indicated in the micrograph.
0,* o
.
one crystal
with a disordered
5 (0.112) Mn.Er(O.ll2)
Mn,%S,,
. . ..(4.4.3f.*..
qMnEr,S,
*..*(4,4)*...
+ MnEr,S,
.“*(4,3)*.”
b
0.. 5 lO.ll2) o,.Mn.EdO.ll2)
Mvr, 3,
. . ..(4.4.4,3)***. =MnEr S
2 4
=2MnEr,S,
. ..*(4.4).... .*.+(4,4)**..*
l
Mn,Er,S,,
..**(4,4,3f*...
MnEr,,S,
. ..*(4.3)**.*
Fig. 4. Structural models of (a) MnzEr eS rr, (b) Mn3ErsSrs (after Hyde et al. [ 2 - 41). Phase - deeI (A) 12.7 A.. (4,4). . 4 x dl,,,, 10.9 B (4,3). . 3x T4 x d{lU) c (4,4,4,3). . 23.7 - d(A) + d(B) 34.7 - d(A) + 2d(B). D..(4,4,3)2..
phases
projected
=
along
[OlO]
374
Acknowledgment One of us (L.C.O.) wish to acknowledge with appreciation discussions with Professor B. G. Hyde, R.S.C., A.N.U., Canberra, and for the use of his electron microscope (JEOL 200 CX).
valuable Australia,
References 1 C. Adolphe, Ann. Chim. (Paris), 10 (1965) 271. 2 S. Andersson and B. G. Hyde, J. Solid State Chem., 9 (1974) 92. 3 B. G. Hyde, S. Andersson, M. Bakker, C. M. Plug and M. O’Keeffe, Prog. Solid State Chem., 12 (1979) 273. 4 M. Bakker and B. G. Hyde, Phitos. Mug. A, 23 (1978) 615. 5 A. Prodan, M. Bakker, M. Versteegh and B. G. Hyde, Phys. Chem. Miner., 8 (1982) 188. 6 D. Colaitis, D. van Dyck and S. Amelinckx, Phys. Status Solidi (AI, 68 (1981) 49.