FeS2 (Pyrite)

Basic Info

Pyrite, formally known as Iron disulfide, is the most abundant naturally occurring of the sulfide minerals.  It has a crystal structure that resembles the fluorite structure. Iron disulfide has a yellow-brass, metallic luster that is sometimes incorrectly recognized as gold. Due to this mistaken identity it is often referred to as “fool’s gold”. 1

As the result of sparks generated when struck against metal, pyrite was used as a source of ignition for early firearms. Pyrite is also used for commercial production of sulfur dioxide, which is used in the paper industry as well as in the manufacture of sulfuric acid. Fool’s gold also has applications in jewelry, mineral detection in radio receivers, and photovoltaics. 1

Crystal Structure

   

 

  

  Fractional Coordinates Orthogonal Coordinates
Label Elmt x y z xor[Å] yor[Å] zor[Å]
1. Fe 0.0000 0.0000 0.0000 0.000 0.000 0.000
2. Fe 0.5000 0.0000 0.5000 2.862 0.058 2.544
3. Fe 0.5000 0.5000 0.0000 2.646 2.765 -0.157
4. Fe 0.0000 0.5000 0.5000 0.102 2.709 2.705
5. Fe 1.0000 0.0000 0.0000 5.405 0.114 -0.318
6. Fe 1.0000 0.5000 0.5000 5.507 2.823 2.387
7. Fe 0.0000 1.0000 0.0000 -0.114 5.415 0.004
8. Fe 0.5000 1.0000 0.5000 2.748 5.473 2.548
9. Fe 1.0000 1.0000 0.0000 5.291 5.529 -0.314
10. Fe 0.0000 0.0000 1.0000 0.318 0.003 5.407
11. Fe 0.5000 0.5000 1.0000 2.964 2.767 5.250
12. Fe 1.0000 0.0000 1.0000 5.723 0.117 5.089
13. Fe 0.0000 1.0000 1.0000 0.204 5.417 5.411
14. Fe 1.0000 1.0000 1.0000 5.609 5.532 5.093
15. S 0.3849 0.3849 0.3849 2.159 2.129 1.960
16. S 0.8849 0.3849 0.1151 4.776 2.185 0.343
17. S 0.1151 0.8849 0.3849 0.644 4.806 2.048
18. S 0.6151 0.8849 0.1151 3.261 4.862 0.430
19. S 0.6151 0.6151 0.6151 3.450 3.403 3.133
20. S 0.1151 0.6151 0.8849 0.833 3.346 4.750
21. S 0.8849 0.1151 0.6151 4.966 0.726 3.045
22. S 0.3849 0.1151 0.8849 2.349 0.670 4.662

 

Theoretical diffraction data using a Cu Kα monochromatic source.

(m is the multiplicity and N is the maximum number of flexions)

ref no. h k l d(hkl) 2-Theta Intensity I/Imax m N
[ 1] 1 1 1 3.12693 28.5207 3.45405e-002 37.7 8 3
[ 2] 0 0 2 2.70800 33.0502 8.38185e-002 91.5 6 4
[ 3] 0 2 1 2.42211 37.0850 4.90083e-002 53.5 12 5
[ 4] 1 1 2 2.21107 40.7741 4.07521e-002 44.5 24 6
[ 5] 0 2 2 1.91485 47.4381 4.57922e-002 50.0 12 8
[ 6] 1 2 2 1.80533 50.5106 5.56486e-004 0.6 24 9
[ 7] 1 1 3 1.63299 56.2871 9.15808e-002 100.0 24 11
[ 8] 2 2 2 1.56346 59.0306 1.45073e-002 15.8 8 12
[ 9] 0 2 3 1.50213 61.6974 1.49215e-002 16.3 12 13
[10] 1 2 3 1.44749 64.2989 2.01434e-002 22.0 48 14
[11] 0 0 4 1.35400 69.3429 3.85639e-005 0.0 6 16
[12] 0 4 1 1.31357 71.8008 6.67362e-004 0.7 36 17
[13] 1 1 4 1.27656 74.2244 3.85281e-004 0.4 24 18
[14] 1 3 3 1.24252 76.6194 9.79268e-003 10.7 24 19
[15] 0 2 4 1.21105 78.9908 1.25237e-002 13.7 24 20
[16] 1 2 4 1.18187 81.3432 8.38154e-003 9.2 48 21
[17] 2 3 3 1.15470 83.6810 4.14859e-003 4.5 24 22
[18] 2 2 4 1.10554 88.3290 1.21383e-002 13.3 24 24
[19] 0 4 3 1.08320 90.6469 3.45885e-004 0.4 12 25
[20] 1 3 4 1.06217 92.9660 5.11313e-004 0.6 48 26
[21] 1 1 5 1.04231 95.2899 3.31754e-002 36.2 32 27
[22] 0 2 5 1.00573 99.9680 1.10694e-002 12.1 60 29

 

Photovoltaic Applications

The primary method of pyrite for photovoltaic applications is that of thin-films. It demonstrates extremely promising results for the use as the active layer in solar photovoltaic and photoelectrochemical cells. Pyrite has a suitable band gap (Eg = 0.95 eV), effective light absorption (R > 105 cm-1 for hν > 1.3 eV), an adequate minority carrier diffusion length (100-1000 nm), and for all intensive purposes is in infinite elemental abundance. In principle, all of U.S. primary power demand (∼3.5 TW) could be met with 10% of the pyrite that is disposed annually as mining waste in six U.S. states alone (assuming 10% cell efficiency and a conservative 5 μm thick pyrite active layer). 2

 

Basic Parameters at 300 K

Crystal structure: Fluorite 3
Group of symmetry: Pa(-3) 3
Number of atoms in 1 cm3: 7.55*1022 3
Unit cell volume: 158.8678 Å3 3
Atoms per unit cell: 12 3
Auger recombination coefficient C: 10-26 cm6 s-1 3
Debye temperature: 6*106 K 4
Density: 5.0159 g/cm3 3
Dielectric constant: ɛ=10.9 5
Effective electron density: Nc = 3*1018 cm-3 5
Effective electron masses: me* = 0.25me 5
Effective hole density: Nv = 3*1019 ± 5*1019 cm-3 5
Effective hole masses: mh* = (2.2 ± 0.7) me 5
Lattice constant: 5.416 Å 6
Optical phonon energy: 1.048 ± 0.005 eV 4

Band structure and carrier concentration

Graph on the amount of photo-generated carriers as a function of thickness of the planar pyrite and silicon film may be found in Pietro P. Altermatt et al. 5

Graph of Majority carrier mobility as a function of majority carrier density of natural and synthetic pyrite crystals and of pyrite thin films can be found in Pietro P. Altermatt, Tobias Kiesewetter, Klaus Ellmer, Helmut Tributsch, Specifying targets of future research in photovoltaic devices containing pyrite (FeS2) by numerical modelling, Solar Energy Materials and Solar Cells, Volume 71, Issue 2, 1 February 2002, Pages 181-195, ISSN 0927-0248, 10.1016/S0927-0248(01)00053-8.5 

Graph of the lifetime of excess carriers as a function of majority carrier density for various Auger coefficients C can be found in Pietro P. Altermatt et al. 5

Temperature Dependency

Graph of optical absorption edge as a function of temperature may be found in C de las Heras et al 4

Donors and Acceptors

Donors: Ni, Co 1

Acceptors: As 1

Electrical Properties

 
Energy gap: 0.95 eV 6
Energy spin-orbital splitting: 1.2 eV 7
Intrinsic carrier concentration: 2.78*1012 cm-3 5
Carrier mobility: 120 cm2 V-1 s-1 4
Intrinsic resistivity: 0.18 Ω·cm 4

Basic Parameters of Electrical Properties

Mobility and Hall Effect

 
Mobility parameters:  µmax = 300 cm2 / V s  5
  µmin = 0.02 cm2 / V s  5
  cref = 6*1017 cm-3 5
  β = 1.3  5

              

Optical properties

 
Refractive index   nref = 4.5 on average   5
Absorption coefficient   5*105 cm-1 (λ<750nm) 5

Thermal properties

Mechanical properties, elastic constants, lattice vibrations

Basic Parameters

Bulk modulus:   143 GPa 6
Density:     5.0159 g/cm3   
Hardness: 6.3 on the Mohs scale   
Surface microhardness (using Knoop's pyramid test):

792 kg/mm2 @ 100 Gms load 

577 kg/mm2 @ 300 Gms load 

  
Cleavage planes:    (1 1 0), (1 1 1), (0 0 1)     

Elastic Constants

  C11 = 3.46-3.818 Mbars  
C12 = -0.529-0.34 Mbars   
C44 = 0.68-1.187  Mbars   

Data on Raman spectrum of polycrystalline thin film may be found in C de las Heras et al 4

The development of these pages on photovoltaic materials’ properties was carried out at the University of Utah primarily by undergraduate students Jeff Provost and Carina Hahn working with Prof. Mike Scarpulla. Caitlin Arndt, Christian Robert, Katie Furse, Jash Sayani, and Liz Lund also contributed. The work was fully supported by the US National Science Foundation under the Materials World Network program award 1008302. These pages are a work in progress and we solicit input from knowledgeable parties around the world for more accurate or additional information. Contact [email protected] with such suggestions.