Cai Hu team of Nanchang University successfully designed and synthesized a ceramic like molecular ferroelectrics

Under the guidance of the "ball like non ball" theory proposed by Professor Xiong rengen, a famous molecular ferroelectric scientist in the world, recently, Cai Hu's team of Nanchang University successfully designed and synthesized a ceramic like molecular ferroelectric [3,2,1-dabco] BF 4 At room temperature, the molecular ferroelectrics show excellent ferroelectric properties and film-forming properties The relevant research results were published in Journal of the American Chemical Society (DOI: 10.1021 / JACS 9b11665), the top journal in the field of chemistry, under the title of "rational design of ceramic molecular ferroelectric by quantitative theory" The first author of this paper is Dr Wei Zhenhong, and the first completion unit and corresponding author unit are Nanchang University This is the first case of anti perovskite molecular ferroelectrics reported on JACS in 2018, and Cai Hu's team has made important research progress in the field of molecular ferroelectrics again Fig 1 (a) schematic diagram of synthesis strategy of ceramic molecular ferroelectrics [3.2.1-dabco] BF 4, (b) cubic symmetric structure of molecular [3.2.1-dabco] BF 4 (source: J am Chem SOC.) at present, inorganic ceramic ferroelectrics (such as PZT, SBT, BTO) are limited in their application in flexible wearable devices due to their high film-forming cost, high-temperature sintering required for preparation and potential toxic elements In contrast, molecular ferroelectric materials are widely concerned by researchers because of their easy processing, environment-friendly, light weight, low acoustic impedance and mechanical flexibility, which can be used as a feasible substitute or beneficial supplement for conventional ceramic ferroelectric materials However, there are only a few reports on the polycrystalline ceramic molecular ferroelectrics induced by plastic phase transformation, and most of them show uniaxial ferroelectric properties, which greatly limits their potential in practical applications Figure 2 [3,2,1-dabco] BF 4 ferroelectric properties test and characterization (source: J am Chem SOC.) in this work, the research team used the "ball like non ball" theory to synthesize a kind of ceramic molecular ferroelectrics with m3mfmm2 ferroelectric phase transition on 357k by chemical design method, 5-diazabicyclo [3.2.1] octane boron tetrafluoride ([3.2.1-dabco] BF 4) It can show excellent ferroelectric properties in the form of polycrystalline films at room temperature Based on the reported 4 / mmmfmm2 molecular ferroelectric [2.2.2-dabco] BF 4, the [2.2.2-dabco] + cation is changed to its isomer [3.2.1-dabco] +, which reduces the molecular symmetry and maintains the quasi spherical molecular configuration to a certain extent, so that its polar axis is increased from 2 to 6, and its spontaneous polarization intensity PS is increased from 4.9 μ C · cm-2 It increased to 5.5 μ C · cm - 2 It is worth mentioning that the design idea successfully expands the transformation of ferroelectric phase transition from tetragonal system to orthorhombic system to the transformation from cubic system to orthorhombic system The great symmetry breaking in ferroelectric phase transition is beneficial to increase the entropy value from ferroelectric phase to paraelectric phase The discovery will provide a new way to reduce the energy loss in the field of refrigeration, and it is a new breakthrough of molecular ferroelectric in the field of solid refrigeration This work also provides a new design idea for the synthesis of ceramic like molecular ferroelectrics, greatly improving its application potential in wearable devices, flexible materials, biological machinery and other fields.