I have green synthesized TiO2 nanoparticles. For my experiment purpose, I tried doping the TiO2 NPs with Cu and Ag. Cu2+ ion has radii of 0.72 angstrom and Ag+ ion has around 115 angstrom whereas, Ti4+ ion has around 0.68-angstrom radii. In both of the cases, doping element is bigger than the base element. So, the doping elements will create a COMPRESSIVE STRESS in the lattice.
All my doped samples (both Cu and Ag), showed a LEFT side shift from the prime peak line (undoped TiO2). Meaning, the Bragg angle became smaller as I increased the doping percentage.
What should be the main reason for this?
I'm not sure why you think larger ions will compress the crystal lattice, generally speaking larger ions will expand the lattice, which is consistent with a shift to lower angle.
Hi Fnu Asrafuzzaman
You have doped Cu2+ and Ag+ into TiO2 where both the doped metal ions are a greater ionic radius than the Ti4+. First, calculate any change in crystallite size/volume due to doping and also check the stress, strain, and dislocation density using the Williamson-Hall (W-H) plot and compare with the undoped TiO2. The Williamson-Hall (W-H) plot will help a lot. From my side, I can the above.
For more about Williamson-Hall (W-H) plot, you may go through the following:
org/10.1016/j.apcatb.2017.03.055, org/10.1016/j.jes.2019.09.004
Regards
It is simply because of change in crystal lattice properties ..
Nicely explained by Dr. @Arnab Mukherjee
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