Study on the crystal structure using the powder method for XRD refinement and the hydration state of halloysite

Halloysite is an intelligent nano-mineral material available in abundance and at a low price. However, due to the poor crystallization performance, the current data on the crystal structure of halloysite are insufficient. This paper will compare and analyze the crystal structure of halloysite and kaolinite in the kaolin subgroup. Using the x-ray powder diffraction data, the crystal structure of halloysite is refined by Rietveld’s least square full spectrum fitting method. Compared with the crystal structure of kaolinite, the crystal structure of halloysite contains a small amount of interlayer water molecules. Through structural refinement verification, each unit cell contains 0.121 interlayer water molecules, and the water molecules are at the center of the interlayer area corresponding to the hexagonal ring of the tetrahedron layer.