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Synthesis and Characterization of a Pb 1-x Sr x CrO 4 Solid Solution. Ohio State University CHEM 123 REEL Poster Session. Matthew W. Stoltzfus Thad Matta Jim Tressel Bob Todd. 22 May 2007. Pb(SbO 3 ) 2. CdS. PbCrO 4. Goals. - PowerPoint PPT Presentation
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Synthesis and Characterization of a Pb1-xSrxCrO4 Solid Solution
Ohio State UniversityCHEM 123 REEL Poster Session
Matthew W. StoltzfusThad MattaJim TresselBob Todd
22 May 2007
Goals
What are the goals of your research. What scientific concepts are you trying to understand?
What pigments are you trying to replace and why?
Pb(SbO3)2 CdS PbCrO4
Traditional pigments:
Synthesis: End Members
2 PbCO3 + Cr2O3 + 3/2 O2 2 PbCrO4 + 2 CO2
Cr2O3 + 2 SrCO3 + 3/2 O2 2 SrCrO4 + 2 CO2
9 PbCO3 + 5 Cr2O3 + SrCO3 + 15/2 O2 10 Pb0.9Sr0.1CrO4 + 10 CO2
8 PbCO3 + 5 Cr2O3 + 2 SrCO3 + 15/2 O2 10 Pb0.8Sr0.2CrO4 + 10 CO2
5 PbCO3 + 5 Cr2O3 + 5 SrCO3 + 15/2 O2 10 Pb0.5Sr0.5CrO4 + 10 CO2
2 PbCO3 + 5 Cr2O3 + 8 SrCO3 + 15/2 O2 10 Pb0.2Sr0.8CrO4 + 10 CO2
PbCO3 + 5 Cr2O3 + 9 SrCO3 + 15/2 O2 10 Pb0.1Sr0.9CrO4 + 10 CO2
All reactions were carried out using traditional solid state synthesis overnight at 750°C.
Synthesis: Solid Solution
2 PbCO3 + Cr2O3 + 3/2 O2 2 PbCrO4 + 2 CO2
Cr2O3 + 2 SrCO3 + 3/2 O2 2 SrCrO4 + 2 CO2
9 PbCO3 + 5 Cr2O3 + SrCO3 + 15/2 O2 10 Pb0.9Sr0.1CrO4 + 10 CO2
8 PbCO3 + 5 Cr2O3 + 2 SrCO3 + 15/2 O2 10 Pb0.8Sr0.2CrO4 + 10 CO2
5 PbCO3 + 5 Cr2O3 + 5 SrCO3 + 15/2 O2 10 Pb0.5Sr0.5CrO4 + 10 CO2
2 PbCO3 + 5 Cr2O3 + 8 SrCO3 + 15/2 O2 10 Pb0.2Sr0.8CrO4 + 10 CO2
PbCO3 + 5 Cr2O3 + 9 SrCO3 + 15/2 O2 10 Pb0.1Sr0.9CrO4 + 10 CO2
All reactions were carried out using traditional solid state synthesis overnight at 750°C.
Color and UV-Vis Spectra: End Members
PbCrO4 SrCrO4Pb0.9Sr0.1CrO4 Pb0.8Sr0.2CrO4 Pb0.5Sr0.5CrO4 Pb0.2Sr0.8CrO4 Pb0.1Sr0.9CrO4
0
10
20
30
40
50
60
70
80
90
100
400 450 500 550 600 650 700 750
Wavelength (nm)
Ref
lect
ance
PbCrO4
Pb(0.9)Sr(0.1)CrO4
Pb(0.8)Sr(0.2)CrO4
Pb(0.5)Sr(0.5)CrO4
Pb(0.2)Sr(0.8)CrO4
Pb(0.1)Sr(0.9)CrO4
SrCrO4
Color and UV-Vis Spectra: Solid Solution
PbCrO4 SrCrO4Pb0.9Sr0.1CrO4 Pb0.8Sr0.2CrO4 Pb0.5Sr0.5CrO4 Pb0.2Sr0.8CrO4 Pb0.1Sr0.9CrO4
0
10
20
30
40
50
60
70
80
90
100
400 450 500 550 600 650 700 750
Wavelength (nm)
Ref
lect
ance
PbCrO4
Pb(0.9)Sr(0.1)CrO4
Pb(0.8)Sr(0.2)CrO4
Pb(0.5)Sr(0.5)CrO4
Pb(0.2)Sr(0.8)CrO4
Pb(0.1)Sr(0.9)CrO4
SrCrO4
X-Ray Diffraction Data: Solid Solution
20 22 24 26 28 30 32 34 36 38 40
PbCrO4 Pb0.9Sr0.1CrO4 Pb0.8Sr0.2CrO4 Pb0.5Sr0.5CrO4 Pb0.2Sr0.8CrO4 Pb0.1Sr0.9CrO4 SrCrO4
SrCrO4
PbCrO4
The XRD patterns show the SrCrO4 and PbCrO4 form a complete solid solution from x = 0.0 to x = 1.0.
Isothermal Phase Diagram: Solid Solution
SrCrOSrCrO44PbCrOPbCrO44
Complete Solid Solution, Pb1-xSrxMoO4
Increasing Sr
x=0 x=0.2 x=0.5 x=0.8 x=1.0
SrSr PbPb CrOCrO44
Monoclinic Monoclinic
Origins of Color
What electronic excitations are responsible for color in each of your end members?
What electronic excitations are responsible for color across your solid solution? Why/how might you expect the color to vary across the solid solution?
Band Gaps (or Absorption Peaks)
PbCrO4 SrCrO4Pb0.9Sr0.1CrO4 Pb0.8Sr0.2CrO4 Pb0.5Sr0.5CrO4 Pb0.2Sr0.8CrO4 Pb0.1Sr0.9CrO4
2.27 eV 2.27 eV 2.32 eV 2.41 eV 2.48 eV 2.50 eV 2.53 eV
Band Gap as a Function of Composition
2.25
2.30
2.35
2.40
2.45
2.50
2.55
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Composition of x
Ban
d G
ap (e
V)
Be sure to define which composition corresponds to x = 0 and which to x = 1.
Conclusions and Future Directions
Did you form a solid solution? If so over what composition ranges?
What colors were your samples? Are the colors what you would expect from the UV-Vis spectra? How did the band gap vary as a function of composition? Would these samples make good pigments?
What would you do next to reach the goal stated on the first slide? What other compositions might be tried? What have you learned about the relationship between composition, optical absorption and color?