I have synthesized TiO2 nanoparticles by TiCl3 and NaOH. The NaOH is added to Ticl3 solution to make the pH 8.7. and then stirred for 2 hours until the purple color became white. The precipitate was centrifuged 4 times and dried. I took XRD of these nanoparticles, which shows much noise in the base line ( fig. attached). Same day I took XRD of ZnO sample, which don't have any noise in the baseline. From this any error due to instrument is overruled. Is there anything to keep in mind during the synthesis process.
Looking at your synthesis method, there are several likely causes for the noisy baseline in your TiO₂ XRD pattern (especially since your ZnO from the same day looks clean):
How to fix it:
- Wash more thoroughly ; try 6+ centrifuge cycles, maybe using some ethanol in the later washes
- Heat treat your sample , either calcine at about 400°C for 2 hours or try hydrothermal treatment (80°C in a sealed container overnight)
- Grind your sample better before XRD to reduce surface roughness
- Try slower NaOH addition during synthesis to get more uniform particles
Since your ZnO looks good, we know it's not the XRD machine. The heat treatment will probably make the biggest difference , it converts amorphous material to crystalline and removes those hydroxide groups that contribute to background noise.
use origin or jade softwire to make it smooth. this is not a problem you can use the same spectra
Please provide more details on how you measure it, which sample holder, and the amount of sample on the sample holder. I see that XRD is measuring the sample holder too, which will contribute to the background. Or something amorphous is present in the sample. How to correct it, measure an empty background and subtract it from the measured data. or use smoothing (spline) to reduce the noise (if you are only interested in phase identification)
Seyed makes some good points, but ...
1. I must disagree, failing to rinse away all of the NaCl will give NaCl peaks, not an elevated background.
3. Maybe, but you do at least one phase non-nano sized crystallites. This sounds like just a special case of 2. Nanocrystalline materials still generally have recognizable peaks, and do not result in a uniformly elevated backgroud.
2 and 4. Yes, the phases mentioned may be amorphous.
re Seyed's how to fix:
- "Wash more ..." Do you see NaCl peaks? If not, this won't help. NaCl will not be amorphous.
- "Heat treat..." sounds like a good idea
- "Grind ... to reduce surface roughness" Wait! Why are we talking about surface roughness?! You do ideally want cyrstallites in the 1 - 10 micron size range, but this is not to reduce background. If particles are already small, you may amorphize them, so only grind if you particles are large.
- "Try slower..." No argument.
Another cause of elevated background: Ti will have signification fluorescence due to Cu Kalpha radiation. Zn will not. Thus expect Ti-rich samples to have much higher backgrounds that Zn-rich samples.
As Imran implies, if you are using a microscope slide for your sample holder, for your Ti compounds, the low density and low Z material may be allowing x-rays to penetrate the sample and give amorphous background from the sample holder. When using Zn compounds, the x-ray absorption will be much higher, thus preventing contributions from the sample holder.
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