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The structure and stability of manganese gallium sulfide
Mat. Res, Bull. Vol. 8, pp. I079-i082, 1973. Printed in the United States.
P e r g a m o n Press, Inc.
THE STRUCTURe. AND STABILITY OF MANGANESE GALLIUM SULFIDE
P. Viswanadham and J. G. Edwards University of Toledo, Toledo, Ohio 43606, U. S. A.
(Received July 16, 1973; C o m m u n i c a t e d by J. S. Anderson) ABSTRACT The structure and stability of manganese gallium sulfide was investigated in the ranges 800-1030 ° and 0-1 atm. Several new phases including a spinel, a tetragonal one, and a hexagonal one were identified. Lattice parameters, densities, melting point, and chemical analyses are reported.
Introduction Since the discovery of ferromagnetism and semiconducting properties of sulfospinels and selenospinels of chromium (1,2), electrical, m~gnetic, and structural properties of chalcogenide spinels and related compounds have been investigated extensively owing to their research and industrial applications.
Thermodynamic and phase studies of these compounds, although
of great importance, have been less numerous. Hahn and Klinger (3) in 1950 and Schlein (4) in 1971 reported the preparation and properties of MnIn2S 4 spinel. the spinel form of MnA12S 4.
Donohue (5) in 1970 reported
The gallium analogue has not been reported.
Flahaut et al. (6) in 1963 observed several definite compounds between the compositions 2Ga2S3-MnS and Ga2S3-MnS in the Ga2S3-MnS system. noted that MnGa2S 4 has three modifications.
They also
Yokota et al. (7) in 1971
studied the high pressure phase transformations in MnA12S 4 and MnGa2S 4 and reported six polymorphs of MnGa2S 4 in the lO to 95 kb pressure range. this paper we report investigation and characterization of several new low-pressure phases in the Mn-Ga-S system. 1079
In
1080
MANGANESE GALLIUM SULFIDE
Vol. 8, No. 9
Experimental Manganese, gallium, and sulfur in the molar ratio 1:2:4 were combined in an evacuated sealed Vycor tube by heating at 500 ° until some sulfur reacted, than at 800 ° for 5-6 days.
Debye-Scherrer X-ray powder patterns
of the product were obtained and analyzed.
A portion of the product was
heated in a molybdenum effusion cell in a radlo-frequency induction vacuum furnace at 1030°I X-ray powder patterns of the residues were obtained. Four experiments were conducted with portions of the product in evacuated sealed Vycor tubes:
(1) Heating in an 8-1n. long tube in a temperature
gradient of 500-915 °. 34 hours at lO15 °.
(2) Heating for six days at 985 °.
(3) Heating for
(4) Heating to discrete temperatures between 900 and
lO00 °, in increasing order, for periods of several hours! after each heating the tube being quenched in air and examined visually.
After each
of the four experiments the tube was quenched in air then the sample was removed and examined visually and by X-ray powder diffraction.
Densities
of the product of the sealed tube preparation and of the product of the sealed tube heating at 985 ° were determined by a hydrostatic techniquel the magnetic susceptibility of the former was measured by the Gouy balance method.
Chemical analyses of the products of the sealed tube heating at
985 ° were done by determining manganese colorimetrlcally, sulfur gravimetrically as barium sulfate, and gallium by difference. Results and Discussion The product of the sealed tube preparation was a green homogeneous powder (I ').
Analysis of the X-ray powder pattern of the green product
revealed & cubic spinel phase (I) with a lattice parameter of 10.42 + 0.05 along with 1-9% of unidentified phases.
The density of the green powder
(I') was 3.67 + 0.14 g cm "3 and its magnetic susceptibility was 5 . 2 6 ~ o . The temperature gradient experiment yielded three sublimates and a residue: in the coolest region was gallium sulfide, then a pink sublimate (II), then a green sublimate identical to the green starting material (I '), then the residue at the hot end which was MnS. Heating (I') at I 0 1 ~ melted it and produced two phases, pink truncated hexagonal-bipyramidal crystals (III) and a gray mass (IV). The X-ray powder pattern of (III) was indexed as hexagonal with lattice parameters a ~ 7.03 ~ and c = 9.63 ~.
The gray mass was not identified.
Heating (I')~at 985 ° produced a pink phase (V) and a black phase (VI) with nearly identical X-ray powder patterns l no other phase was in the tube.
Vol. 8, No. 9
MANGANESE GALLIUM SULFIDE
1081
Neither X-ray pattern could be indexed as cubic, tetragonal, or hexagonal. The pink phase (V) had a density of 3.40 g cm-3~ chemical analysis gave 16.36 + 0,07~ Mn and 43.11 + 0.3%S, thence an empirical formul~ Mn2Ga4S 9. Manganese content of the black phase (VI) was 16.73 + 0.07%.
Heating (I')
at discrete temperatures gave the pink phase (II) at 950°, the green powder (I') at 960 ° , and the pink phase (V) at 970 ° . The sample melted at 995 ° . The lattice parameter of the spinel (I) compares well with the value 10.39 ~ interpolated from the lattice parameters of MnA12S 4 spinel, 10.09 (5), and Mnln2S 4 spinel, 10.69 ~ (3). The density of the green product (I'), 3.67 g cm "3, is in good agreement with a density of 3.78 g cm "3 calculated from unit cell volume, formula weight of MnGa2S4, eight formula units per unit cell (8), and Avogadro's number.
Probably the density is influenced by
the presence of the unidentified phases. The powder pattern of the pink tetragonal phase (II) shows remarkable similarity to that of ZnGa2S 4 (9). The lattice parameters of tetragonal MnGa2S 4 and ZnGa2S 4 are compared in Table 1.
Three factors seem relevant in
the elucidation of structural similarities of these two compounds,
The
TABLE 1 Lattice Parameters of Pink Tetra~onal MnGa2S 4 (II) and of ZnGa2S 4. Parameter
MnGa2S 4 (this work)
ZnGa2S 4 (9)
c
9.94
a
5.47 ~
5.26
1.81
1.97
c/a
i0.4
ionic radii of Zn 2+ and Mn 2+ are nearly the same, 0.74 ~ and 0.80 ~, respectively.
Both Zn 2* in d l0 configuration and Mn 2+ in d 5 high spin configu-
ration have zero crystal field stabilization energy and spherical charge distribution (lO). The green color of phase (i) indicates that the manganese ions predominantly occupy octahedral sites as in green MnS, thus the spinel is inverse or mixedl the magnetic susceptibility, 5.26 ~ o , Mn 2+ is in the high spin state.
indicates that
In the pink tetragonal phase (II), stable
at 950°, the manganese ions occupy tetrahedral sites.
A change from cubic
to hexagonal close packing occurs at higher temperatures to produce the
108Z
MANGANESE
hexagonal phase ( i I I ) .
GALLIUM
SULFIDE
Vol. 8, No. 9
The low manganese contents of phases (V) and (VI)
with r e s p e c t t o t h a t of MnGa2S4, 17.03%, could be due to valence changes from Mn II to Mn IYuI or MnIV| compounds of Mn III and MnIV are usually pink
and black (lO), the colors of phases (V) and (VI), respectively.
However,
no consequent manganese-rlch phase was discovered with phases (V) and (VI), hence the low manganese content remains to be explained. Manganese gallium sulfide exhibits a large variety of phases.
Coordi-
nation, packing, and valence disproportionatlons affect phase transformations in the manganese gallium sulfur system.
Possibly iml~rtant factors
not identified in this work are MnS/Ga2S 3 stoichiometry changes (6), defect structtLres (ll), and manganese high-spin low-spln transformations. Acknowledgement We gratefully acknowledge the financial support of Owens-Illinois, Toledo, Ohio. References 1. P. K. Baltzer, H. W. Lahmann, and M. Robbins, Phys. Rev. Lett. 15, 493
(1965). 2. N. Menyuk, K. Dwight, and R. J. Arnott, J. Appl. Phys. 37, 1387 (1966). 3. H. Hahn and W. Kllnger, Z. Anorg. Allg. Chem. 26~, 177 (1950). 4. W. Schleln S. and A. Wold, J. Solid State Chem. 4, 286 (1972). 5. P. C. Donohue, J. Solid State Chem. 2, 6 (1970). 6. J. Flahaut, L. Domange, M. Patrie, A. M. Bostsarron, and M. Guittazd, Nonstoichiometric Compounds, p.179. American Chemical Society, Washington, D. C. (1963). 7. M. Yokota, Y. Syono, and S. Minomura, J. Solid State Chem. 3, 520 (1971). 8. J. W. Verwey and E. L. Heilmann, J. Chem. Phys. 15, 174 (1947). 9. H. Hahn, g. Frank, W. Klin~er, A. D. StSrger, and G. StShzger, Z. Anorg. Allg. Chem. 279, 241 (1955). lO. F. A. Cotton and G. Wilkinson, Advanced Inorganic Chemistry, John Wiley and Sons, New York (1972). ll. R. E. Vandenberghe, G. G. Robbrecht, and V. A. M. Brabers, Mat. Res.
Bun. 8, 571 (1973).
P e r g a m o n Press, Inc.
THE STRUCTURe. AND STABILITY OF MANGANESE GALLIUM SULFIDE
P. Viswanadham and J. G. Edwards University of Toledo, Toledo, Ohio 43606, U. S. A.
(Received July 16, 1973; C o m m u n i c a t e d by J. S. Anderson) ABSTRACT The structure and stability of manganese gallium sulfide was investigated in the ranges 800-1030 ° and 0-1 atm. Several new phases including a spinel, a tetragonal one, and a hexagonal one were identified. Lattice parameters, densities, melting point, and chemical analyses are reported.
Introduction Since the discovery of ferromagnetism and semiconducting properties of sulfospinels and selenospinels of chromium (1,2), electrical, m~gnetic, and structural properties of chalcogenide spinels and related compounds have been investigated extensively owing to their research and industrial applications.
Thermodynamic and phase studies of these compounds, although
of great importance, have been less numerous. Hahn and Klinger (3) in 1950 and Schlein (4) in 1971 reported the preparation and properties of MnIn2S 4 spinel. the spinel form of MnA12S 4.
Donohue (5) in 1970 reported
The gallium analogue has not been reported.
Flahaut et al. (6) in 1963 observed several definite compounds between the compositions 2Ga2S3-MnS and Ga2S3-MnS in the Ga2S3-MnS system. noted that MnGa2S 4 has three modifications.
They also
Yokota et al. (7) in 1971
studied the high pressure phase transformations in MnA12S 4 and MnGa2S 4 and reported six polymorphs of MnGa2S 4 in the lO to 95 kb pressure range. this paper we report investigation and characterization of several new low-pressure phases in the Mn-Ga-S system. 1079
In
1080
MANGANESE GALLIUM SULFIDE
Vol. 8, No. 9
Experimental Manganese, gallium, and sulfur in the molar ratio 1:2:4 were combined in an evacuated sealed Vycor tube by heating at 500 ° until some sulfur reacted, than at 800 ° for 5-6 days.
Debye-Scherrer X-ray powder patterns
of the product were obtained and analyzed.
A portion of the product was
heated in a molybdenum effusion cell in a radlo-frequency induction vacuum furnace at 1030°I X-ray powder patterns of the residues were obtained. Four experiments were conducted with portions of the product in evacuated sealed Vycor tubes:
(1) Heating in an 8-1n. long tube in a temperature
gradient of 500-915 °. 34 hours at lO15 °.
(2) Heating for six days at 985 °.
(3) Heating for
(4) Heating to discrete temperatures between 900 and
lO00 °, in increasing order, for periods of several hours! after each heating the tube being quenched in air and examined visually.
After each
of the four experiments the tube was quenched in air then the sample was removed and examined visually and by X-ray powder diffraction.
Densities
of the product of the sealed tube preparation and of the product of the sealed tube heating at 985 ° were determined by a hydrostatic techniquel the magnetic susceptibility of the former was measured by the Gouy balance method.
Chemical analyses of the products of the sealed tube heating at
985 ° were done by determining manganese colorimetrlcally, sulfur gravimetrically as barium sulfate, and gallium by difference. Results and Discussion The product of the sealed tube preparation was a green homogeneous powder (I ').
Analysis of the X-ray powder pattern of the green product
revealed & cubic spinel phase (I) with a lattice parameter of 10.42 + 0.05 along with 1-9% of unidentified phases.
The density of the green powder
(I') was 3.67 + 0.14 g cm "3 and its magnetic susceptibility was 5 . 2 6 ~ o . The temperature gradient experiment yielded three sublimates and a residue: in the coolest region was gallium sulfide, then a pink sublimate (II), then a green sublimate identical to the green starting material (I '), then the residue at the hot end which was MnS. Heating (I') at I 0 1 ~ melted it and produced two phases, pink truncated hexagonal-bipyramidal crystals (III) and a gray mass (IV). The X-ray powder pattern of (III) was indexed as hexagonal with lattice parameters a ~ 7.03 ~ and c = 9.63 ~.
The gray mass was not identified.
Heating (I')~at 985 ° produced a pink phase (V) and a black phase (VI) with nearly identical X-ray powder patterns l no other phase was in the tube.
Vol. 8, No. 9
MANGANESE GALLIUM SULFIDE
1081
Neither X-ray pattern could be indexed as cubic, tetragonal, or hexagonal. The pink phase (V) had a density of 3.40 g cm-3~ chemical analysis gave 16.36 + 0,07~ Mn and 43.11 + 0.3%S, thence an empirical formul~ Mn2Ga4S 9. Manganese content of the black phase (VI) was 16.73 + 0.07%.
Heating (I')
at discrete temperatures gave the pink phase (II) at 950°, the green powder (I') at 960 ° , and the pink phase (V) at 970 ° . The sample melted at 995 ° . The lattice parameter of the spinel (I) compares well with the value 10.39 ~ interpolated from the lattice parameters of MnA12S 4 spinel, 10.09 (5), and Mnln2S 4 spinel, 10.69 ~ (3). The density of the green product (I'), 3.67 g cm "3, is in good agreement with a density of 3.78 g cm "3 calculated from unit cell volume, formula weight of MnGa2S4, eight formula units per unit cell (8), and Avogadro's number.
Probably the density is influenced by
the presence of the unidentified phases. The powder pattern of the pink tetragonal phase (II) shows remarkable similarity to that of ZnGa2S 4 (9). The lattice parameters of tetragonal MnGa2S 4 and ZnGa2S 4 are compared in Table 1.
Three factors seem relevant in
the elucidation of structural similarities of these two compounds,
The
TABLE 1 Lattice Parameters of Pink Tetra~onal MnGa2S 4 (II) and of ZnGa2S 4. Parameter
MnGa2S 4 (this work)
ZnGa2S 4 (9)
c
9.94
a
5.47 ~
5.26
1.81
1.97
c/a
i0.4
ionic radii of Zn 2+ and Mn 2+ are nearly the same, 0.74 ~ and 0.80 ~, respectively.
Both Zn 2* in d l0 configuration and Mn 2+ in d 5 high spin configu-
ration have zero crystal field stabilization energy and spherical charge distribution (lO). The green color of phase (i) indicates that the manganese ions predominantly occupy octahedral sites as in green MnS, thus the spinel is inverse or mixedl the magnetic susceptibility, 5.26 ~ o , Mn 2+ is in the high spin state.
indicates that
In the pink tetragonal phase (II), stable
at 950°, the manganese ions occupy tetrahedral sites.
A change from cubic
to hexagonal close packing occurs at higher temperatures to produce the
108Z
MANGANESE
hexagonal phase ( i I I ) .
GALLIUM
SULFIDE
Vol. 8, No. 9
The low manganese contents of phases (V) and (VI)
with r e s p e c t t o t h a t of MnGa2S4, 17.03%, could be due to valence changes from Mn II to Mn IYuI or MnIV| compounds of Mn III and MnIV are usually pink
and black (lO), the colors of phases (V) and (VI), respectively.
However,
no consequent manganese-rlch phase was discovered with phases (V) and (VI), hence the low manganese content remains to be explained. Manganese gallium sulfide exhibits a large variety of phases.
Coordi-
nation, packing, and valence disproportionatlons affect phase transformations in the manganese gallium sulfur system.
Possibly iml~rtant factors
not identified in this work are MnS/Ga2S 3 stoichiometry changes (6), defect structtLres (ll), and manganese high-spin low-spln transformations. Acknowledgement We gratefully acknowledge the financial support of Owens-Illinois, Toledo, Ohio. References 1. P. K. Baltzer, H. W. Lahmann, and M. Robbins, Phys. Rev. Lett. 15, 493
(1965). 2. N. Menyuk, K. Dwight, and R. J. Arnott, J. Appl. Phys. 37, 1387 (1966). 3. H. Hahn and W. Kllnger, Z. Anorg. Allg. Chem. 26~, 177 (1950). 4. W. Schleln S. and A. Wold, J. Solid State Chem. 4, 286 (1972). 5. P. C. Donohue, J. Solid State Chem. 2, 6 (1970). 6. J. Flahaut, L. Domange, M. Patrie, A. M. Bostsarron, and M. Guittazd, Nonstoichiometric Compounds, p.179. American Chemical Society, Washington, D. C. (1963). 7. M. Yokota, Y. Syono, and S. Minomura, J. Solid State Chem. 3, 520 (1971). 8. J. W. Verwey and E. L. Heilmann, J. Chem. Phys. 15, 174 (1947). 9. H. Hahn, g. Frank, W. Klin~er, A. D. StSrger, and G. StShzger, Z. Anorg. Allg. Chem. 279, 241 (1955). lO. F. A. Cotton and G. Wilkinson, Advanced Inorganic Chemistry, John Wiley and Sons, New York (1972). ll. R. E. Vandenberghe, G. G. Robbrecht, and V. A. M. Brabers, Mat. Res.
Bun. 8, 571 (1973).