Why does X-ray Diffraction Show Disappearing Peaks in CaCoH3?

In summary, the conversation discusses the study of perovskite hydride CaCoH3 using X-ray diffraction. The crystal structure of CaCoH3 is cubic with space group Pm-3m. At the phase transition point, the (111) and (222) peaks weaken and disappear while shifting to higher energy. The discussion also mentions the temperature dependence of electrical resistance, with the R-T slope indicating a metallic behavior. However, at low temperatures, around 4K, the resistance increases, showing an insulating behavior up to 55mK with a 70% increase. The speaker hopes that the sample will exhibit superconductivity, and they wonder why the resistance increases at low temperature. The sample
  • #1
huyen
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Hope somebody can help me.
I am studing perovskite hydride CaCoH3 using X-ray diffraction. CaCoH3 crystallizes with a cubic in space group Pm-3m. At phase transtion point, all peaks weakened gradually, and shifted to higher energy.The (111) and (222) peaks become weak and disappeared . Why that peaks are disappear?.
 
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  • #2
2. To study the temperature dependence of electrical resistance;
The R-T slope showed metallic. But the resistance revealed increase at lowtemperature around 4K, which show insulator up to 55mK (increase 70%). What is effect? I hope my sample beome superconductivity.
 
  • #3
and Why the resistance increase at low temperature. My sample is powder
 

FAQ: Why does X-ray Diffraction Show Disappearing Peaks in CaCoH3?

1. Why do peaks disappear in X-ray diffraction patterns?

In X-ray diffraction, peaks appear when the X-rays are diffracted by the atoms in a crystalline sample, creating a distinct pattern. However, certain factors such as crystal defects, preferred orientation, and sample preparation can cause the peaks to disappear or become weaker.

2. Why do peaks disappear in CaCoH3 X-ray diffraction patterns?

In the case of CaCoH3, the disappearance of peaks in X-ray diffraction patterns can be attributed to the presence of disordered or amorphous regions in the crystal structure. These regions do not contribute to the diffraction pattern, resulting in weaker or missing peaks.

3. Can temperature or pressure affect the appearance of peaks in X-ray diffraction patterns?

Yes, temperature and pressure can also affect the appearance of peaks in X-ray diffraction patterns. Changes in these parameters can cause the atoms in a crystal to vibrate or move, leading to a shift or broadening of the diffraction peaks.

4. How can we prevent disappearing peaks in X-ray diffraction patterns?

To prevent disappearing peaks, it is important to ensure that the sample is well-prepared and free from defects. This includes proper grinding and polishing of the sample, as well as minimizing preferred orientation by using a random powder sample. It is also crucial to carefully control temperature and pressure during the experiment.

5. Can we still obtain useful information from X-ray diffraction patterns with disappearing peaks?

Yes, even with disappearing peaks, X-ray diffraction patterns can still provide valuable information about the crystal structure and composition of a sample. By analyzing the remaining peaks and their relative intensities, researchers can still determine important parameters such as lattice constants and atomic arrangement in the crystal.

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