1. 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

2. 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(SbO 3 ) 2 CdSPbCrO 4 Traditional pigments:

3. Synthesis: End Members 2 PbCO 3 + Cr 2 O 3 + 3/2 O 2 2 PbCrO 4 + 2 CO 2 Cr 2 O 3 + 2 SrCO 3 + 3/2 O 2 2 SrCrO 4 + 2 CO 2 9 PbCO 3 + 5 Cr 2 O 3 + SrCO 3 + 15/2 O 2 10 Pb 0.9 Sr 0.1 CrO 4 + 10 CO 2 8 PbCO 3 + 5 Cr 2 O 3 + 2 SrCO 3 + 15/2 O 2 10 Pb 0.8 Sr 0.2 CrO 4 + 10 CO 2 5 PbCO 3 + 5 Cr 2 O 3 + 5 SrCO 3 + 15/2 O 2 10 Pb 0.5 Sr 0.5 CrO 4 + 10 CO 2 2 PbCO 3 + 5 Cr 2 O 3 + 8 SrCO 3 + 15/2 O 2 10 Pb 0.2 Sr 0.8 CrO 4 + 10 CO 2 PbCO 3 + 5 Cr 2 O 3 + 9 SrCO 3 + 15/2 O 2 10 Pb 0.1 Sr 0.9 CrO 4 + 10 CO 2 All reactions were carried out using traditional solid state synthesis overnight at 750°C.

4. Synthesis: Solid Solution 2 PbCO 3 + Cr 2 O 3 + 3/2 O 2 2 PbCrO 4 + 2 CO 2 Cr 2 O 3 + 2 SrCO 3 + 3/2 O 2 2 SrCrO 4 + 2 CO 2 9 PbCO 3 + 5 Cr 2 O 3 + SrCO 3 + 15/2 O 2 10 Pb 0.9 Sr 0.1 CrO 4 + 10 CO 2 8 PbCO 3 + 5 Cr 2 O 3 + 2 SrCO 3 + 15/2 O 2 10 Pb 0.8 Sr 0.2 CrO 4 + 10 CO 2 5 PbCO 3 + 5 Cr 2 O 3 + 5 SrCO 3 + 15/2 O 2 10 Pb 0.5 Sr 0.5 CrO 4 + 10 CO 2 2 PbCO 3 + 5 Cr 2 O 3 + 8 SrCO 3 + 15/2 O 2 10 Pb 0.2 Sr 0.8 CrO 4 + 10 CO 2 PbCO 3 + 5 Cr 2 O 3 + 9 SrCO 3 + 15/2 O 2 10 Pb 0.1 Sr 0.9 CrO 4 + 10 CO 2 All reactions were carried out using traditional solid state synthesis overnight at 750°C.

5. Color and UV-Vis Spectra: End Members PbCrO 4 SrCrO 4 Pb 0.9 Sr 0.1 CrO 4 Pb 0.8 Sr 0.2 CrO 4 Pb 0.5 Sr 0.5 CrO 4 Pb 0.2 Sr 0.8 CrO 4 Pb 0.1 Sr 0.9 CrO 4

6. Color and UV-Vis Spectra: Solid Solution PbCrO 4 SrCrO 4 Pb 0.9 Sr 0.1 CrO 4 Pb 0.8 Sr 0.2 CrO 4 Pb 0.5 Sr 0.5 CrO 4 Pb 0.2 Sr 0.8 CrO 4 Pb 0.1 Sr 0.9 CrO 4

7. X-Ray Diffraction Data: Solid Solution SrCrO 4 PbCrO 4 The XRD patterns show the SrCrO 4 and PbCrO 4 form a complete solid solution from x = 0.0 to x = 1.0.

8. Isothermal Phase Diagram: Solid Solution SrCrO 4 PbCrO 4 Complete Solid Solution, Pb 1-x Sr x MoO4 Increasing Sr x=0x=0.2x=0.5x=0.8x=1.0 SrPb CrO 4 Monoclinic

9. 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?

10. Band Gaps (or Absorption Peaks) PbCrO 4 SrCrO 4 Pb 0.9 Sr 0.1 CrO 4 Pb 0.8 Sr 0.2 CrO 4 Pb 0.5 Sr 0.5 CrO 4 Pb 0.2 Sr 0.8 CrO 4 Pb 0.1 Sr 0.9 CrO 4 2.27 eV 2.32 eV 2.41 eV 2.48 eV 2.50 eV2.53 eV

11. Band Gap as a Function of Composition Be sure to define which composition corresponds to x = 0 and which to x = 1.

12. 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?