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

[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?.

 

[huyen]

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.

 

[huyen]

and Why the resistance increase at low temperature. My sample is powder