1. Mechanochemical Synthesis of Bismuth
Oxyhalides
Scott Shaw
Department of Physics and Astronomy, The University of Sheffield
Summer Research Presentation, ISL Meeting, Sheffield, UK, 26 September 2014.
ISL_Sheffield

2. Sco- Shaw
Department of Physics and Astronomy
Bismuth Oxyhalides
2
BiOX; X = F, Cl, Br, I
Form a tetragonal matlockite structure.This is a layer structure characterised by [Bi2O2] slabs
interleaved by double slabs of halogen atoms.
Bismuth oxyhalides semiconductors have
demonstrated excellent photocatalyOc acOviOes
and are offering a new family of promising
photocatalysts.
BiOI could be an effecOve storage site for 129I which
remains a significant concern for safe nuclear waste
storage.
BiOCl matlockite structure:
Bismuth atoms shown as grey,
oxygen red, chlorine green

3. Sco- Shaw
Department of Physics and Astronomy
Bismuth Oxyhalides (2)
3
ProducOon of Bismuth oxyhalides is currently done via a wet chemistry route.
BiOX; X = F, Cl, Br, I
Reagents: Bi2O3 and NH4X ; Sigma Aldrich and Alfa Aesar, Purity ≥ 98%
Bi2O3 + 2(NH4X) ➝ 2BiOX + 2NH3 + H20

4. Sco- Shaw
Department of Physics and Astronomy
Mechanochemical Processes
4
Mechanical milling is s-ll mainly used to reduce par-cle size
Mechanically Alloying (MA):
• Dry, high energy milling.
• Used to produce advanced materials.
• This can be seen as Mechanical AcOvaOon.
Mechanochemistry / Reac-on Milling (RM):
• Induce chemical reacOon through solely
mechanical energy.
Commonality
• High Stresses ( 200MPa in a steel ball SPEX mill)
• ParOcles are repeatedly fla-ened, fractured and welded
• Mixing of elements takes place on an atomic scale
• Disordering and dislocaOons are introduced repeatedly
in to the system.
Time to reach similar particle sizes during milling of
Pr16Fe76B8 powder1

5. Sco- Shaw
Department of Physics and Astronomy
Process for Reac-on Milling
5
Fritsch Mini-Mill PulveriseBe 23 is considered a low energy mill
• Milling container: Zirconia Oxide
• Frequency: 30 Hz
• Milling Speed: 0.27ms-1
• Milling Media: Three Spherical 10mm Zirconia Oxide Media
• All milling was conducted at approximately SATP.
• Ball Mass RaOo: Within bounds of between 1/50 and ⅕
• Reagents composiOon: Stoichiometric (Otherwise stated)
• Milling Time: Stated
• Milling Fluid: None otherwise stated.
If stated; sum of reagents mass total 1g with 1ml of fluid

6. Sco- Shaw
Department of Physics and Astronomy
Process for Solid State Synthesis
6
• Reagents masses: Stoichiometric (Otherwise stated)
• Fritsch Mini-Mill PulveriseBe 23 used to mill reagents.
• Under the same condiOons stated previously
• Mill Ome 3 minutes.
• Product was then placed into Aluminium(III) oxide crucibles
• Placed into furnace at 350°C
• Quenched at: (3, 10, 15, 30, 45, 90) minutes intervals

7. Sco- Shaw
Department of Physics and Astronomy
Characterisa-on
7
Diffrac-on PaBern for chemical characterisa-on
Bruker D2 Phaser
Current: 10mA
Voltage: 30kV
Cu Kα X-rayTube: 𝝀 = 1.54184 Å
Range: 20° < 2θ < 60°
Step size: 0.02°
DIFFRAC.EVA sowware on Bruker D2 Phaser
ICDD PDF2 Cards
SEM to view Morphology of products
Hitachi AnalyOcal Benchtop SEM TM3030

8. Sco- Shaw
Department of Physics and Astronomy
Results
8

9. Sco- Shaw
Department of Physics and Astronomy
BiOF Mechanochemical Synthesis
9

10. Sco- Shaw
Department of Physics and Astronomy
BiOF Solid State Synthesis
10
BiOF Solid State Synthesis
: (NH4)2 NO3HF2

11. Sco- Shaw
Department of Physics and Astronomy 11
BiOF: SSS, MS and MS with Carrier
002
The Scherrer equation can be written as:

12. Sco- Shaw
Department of Physics and Astronomy
BiOF SEM Images
12
BiOF MS 150mins BiOF SS 10mins
BiOF MS Hexane 45mins

13. Sco- Shaw
Department of Physics and Astronomy
BiOCl Mechanochemical Synthesis
13

14. Sco- Shaw
Department of Physics and Astronomy
BiOCl Solid State Synthesis
14
Solid State SynthesisSolid State Synthesis

15. Sco- Shaw
Department of Physics and Astronomy
BiOCl: SSS, MS Comparison
15

16. Sco- Shaw
Department of Physics and Astronomy
BiOCl SEM Images
16
BiOCl MS 20hrs
BiOCl SSS 30mins

17. Sco- Shaw
Department of Physics and Astronomy
BiOBr Solid State Synthesis
17

18. Sco- Shaw
Department of Physics and Astronomy
Polymorphs of Bi2O3
18
Bi2O3 + 2(NH4X) ➝ 2BiOX + 2NH3 + H20
Bismuth oxide, Bi2O3 has five crystallographic polymorphs. α, β, γ, δ,
ε.
The room temperature phase, α-Bi2O3 has a monoclinic crystal
structure.
β-Bi2O3 has a structure related to fluorite which is metastable.

19. Sco- Shaw
Department of Physics and Astronomy
BiOI Mechanochemical Synthesis
19
α- Bi2O3

20. Sco- Shaw
Department of Physics and Astronomy
BiOI Mechanochemical Synthesis
20
MS 120 minutes
1.1 x NH4I ; β- Bi2O3

21. Sco- Shaw
Department of Physics and Astronomy
BiOI Solid State Synthesis
21
40% Excess of NH4I

22. Sco- Shaw
Department of Physics and Astronomy
BiOI: SSS, MS and MS with Carrier
22

23. Sco- Shaw
Department of Physics and Astronomy
BiOI SEM Images
23
α- BiOI Mill with Hexane 90mins
α- BiOI Mill 90mins
β - BiOI SSS 75 mins
β - BiOI MS 150 mins

24. Sco- Shaw
Department of Physics and Astronomy
Results Table
24
MS MS with Hexane SSS
BiOF 45 minutes 60 minutes 10 minutes
BiOCl 20 hours - 10 minutes
BiOBr - - 10 minutes
BiOI (α-Bi2O3) 90 minutes 90 minutes Forms BiI3
BiOI (β- Bi2O3) 4 hours
120 minutes
(1.1 x NH4I)
- 45 minutes
(1.4 x NH4I)

25. Sco- Shaw
Department of Physics and Astronomy
Possible Synthesis Route
25
Bi2O3 + 2(NH4X) ➝ 2BiOX + 2NH3 + H20
NH4X ➝ NH3 + HX …(1)
Bi2O3 + HX2 ➝ 2BiOX + H20 …(2)

26. Sco- Shaw
Department of Physics and Astronomy
Oxidation to explain BiI3
26
Bi2O3 + 2(NH4X) ➝ 2BiOX + 2NH3 + H20
4NH4I + O2 à 4 NH3 + 2I2 + 2H2O …(1)

27. Sco- Shaw
Department of Physics and Astronomy
Bi2O3 Polymorphs
27

28. Sco- Shaw
Department of Physics and Astronomy
Amorphisa-on of Bi2O3
28
Compounds can become amorphous during Mechanochemical Processes.
There is an increase in the energy of the milled powder
This is mainly due to the increased volume fracOon of grain boundaries and
disordering.
This increase in energy must raise the free energy to above the level of the
amorphous state.

29. Sco- Shaw
Department of Physics and Astronomy
Amorphisa-on of Bi2O3
29

30. Sco- Shaw
Department of Physics and Astronomy
Future Work
30
• Achieve BiOBr from Mechanochemical Synthesis
• Complete Mechanochemical Synthesis with Hexane for all BiOX
• Achieve SSS for BiOI with reduction in temperature
• Develop a mechanism route for reactions
• See if amorphisaOon of Bi2O3 is possible

31. Sco- Shaw
Department of Physics and Astronomy
Acknowledgements
31
• Prof. N. C. Hya-
• Dr. H. Kinoshita
• Dr. M. Stenne-
• Dr. C. Corkhill
• ISL PhD Students
Bibliography
Wieczorek-Ciurowa, et al. Chem. Soc. Rev., 2013, 42, 7571
P.G. McCormick and F.H. Froes., JOM., 1998, Volume 50, Issue 11, pp 61-65
Olivier Tillement et al J. Mater. Chem., 1999, 9, 305–314
C. Suryanarayana. Progress in Materials Science 46 (2001) 1-184

32. Sco- Shaw
Department of Physics and Astronomy
Ques-ons
32
Any quesOons, comments or suggesOons?