Study On The Structural Phase Transitions In Pentaerythritol And Pentamyl Glycol Binary Systerm

As an important branch of solid-solid phase change materials,polyol organic phase transition energy storage materials have attracted extensive attentions owing to their low phase transition temperature and wide tunable parameters.In the present project,the phase transition process of two typical organic polyol crystals,Pentaerythritol(PE)and Neopentyl glycol(NPG),were studied by using the diamond anvil cell combined with in-house four circle single crystal X-ray diffractometer as well as Raman spectrometer.In addition,the phase transition behavior of PE-NPG mixture under high temperature has also been investigated.Firstly,high-pressure Raman spectroscopy and high-pressure X-ray diffraction measurements for PE single crystal have been carried out.The experimental results reveal that the phase transition of PE single crystal under high-pressure occurred at 2.8 GPa,which is 1.8 GPa lower than previously reported 4.6 GPa,where the body-centered tetragonal structure transforms into the body-centered orthogonal structure.Secondly,the high-pressure Raman spectroscopy and the high-pressure X-ray diffraction experiments for single and powder samples of NPG crystal have been carried out,respectively.The experimental results showed that there were signs of phase change in the range of 1.1 GPa?1.3 GPa and 3.0 GPa?3.2 GPa.It suggests that NPG probably have undergone structural phase transitions within the above mentioned pressure ranges.Last but not least,the four-circle X-ray single crystal diffractometer was used to characterize the high-temperature phase of PE-NPG binary system.The experimental results showed that there are a large number of cluster-shaped PE twins and acicular NPG inverted twins besides a previously reported high temperature phase in the high-temperature treated samples of the binary system.This high temperature phase is found to be a body-centered tetragonal structure with rotating disorder and vibration disorder,rather than the traditional viewpoint as a face-centered cubic structure.