| Phase transition materials are widely used in thermal energy storage and construction fields due to their specific properties of absorbing or releasing energy.Today,with the rapid development of science and technology,scientists are building them into materials for the manufacture of nano and micro-electromechanical sensors.Phase transition materials were gained popularity worldwide and they were considered one of the most promising technologies of the future.Due to the special physical structure of organic-inorganic hybrid perovskites,physical phenomena such as structural phase transition and spontaneous polarization were more likely to occur,making the performance more excellent than traditional phase transition materials.At the same time,the application potential of organic-inorganic hybrid perovskites is far more than that,and it also shines in the fields of solar cells,fluorescence,and semiconductors.Therefore,based on the above analysis,the main content directions is organic-inorganic hybrid perovskite-type multi-functional phase transition materials and anion-cation host-guest crown ether inclusion complex-type multi-functional phase transition materials.The main research contents and results shows below:（1）Two novel Ruddlesden-Popper type two-dimensional organic-inorganic hybrid perovskites（C3H9NI）2（CN2H5）Pb2I7（1）and（C3H9NBr）2（CN2H5）Pb2I7（2）were successfully synthesized.Both compounds has high-temperature phase transitions,and the phase transition temperatures were 382 K/379 K,respectively,and the occurrence of reversible phase transitions was further confirmed by dielectric tests.Compound 1also exhibits excellent fluorescence properties with broad emission at 510 nm,which belongs to the human visible light band.Compounds 1 and 2 also exhibit good semiconducting properties at 1.924 e V and 1.885 e V,respectively.It is believed that these two organic-inorganic hybrid perovskites are expected to become a new generation of multifunctional semiconductor materials.（2）A new one-dimensional organic-inorganic hybrid perovskite compound C5H6NOPb Br3（3）was successfully synthesized.It undergoes a solid-state reversible phase transition at 250 K,and its behavior was confirmed by DSC and dielectric measurements.It also exhibits semiconducting properties with a band gap of 2.78 e V and was smaller than other high-dimensional perovskites.Photoluminescence studies showed that compound 3 has a narrow-band emission at 590 nm and a long lifetime(τav=0.26 ms).This work provides a feasible strategy for designing switchable dielectric phase-change multifunctional materials.（3）A novel anionic and cationic host-guest crown ether inclusion compound（18-Crown-6）（C2H7NCl）（CF3SO3）（4）was successfully synthesized,which underwent a reversible phase transition at 255 K and was confirmed by DSC and dielectric The measurements were confirmed.At the same time,the single crystal test was carried out,and its phase transformation mechanism was analyzed.Compound 4 also has excellent dielectric switching properties and can operated in low temperature environments with various frequencies.Through the nonlinear optical test of compound 4,its SHG intensity was 1.5 times that of KDP.The above analysis shows that compound 4 is expected to become a new generation of dielectric switching phase transition materials with nonlinear optical properties. |
