Room temperature ferroelectric material with extremely low coercive field, large spontaneous polarization value and high Curie temperature and preparation method and application thereof

Abstract

The invention discloses a room-temperature ferroelectric material with an extremely low coercive field, a large spontaneous polarization value and a high Curie temperature and a preparation method and application thereof, the room-temperature ferroelectric material is a zero-dimensional organic-inorganic hybrid perovskite crystal material, has the following chemical formula (C2H8N) 4PbBr6, has the spontaneous polarization value of 2.3 [mu] C / cm < 2 > and the coercive field of 0.11 kV / cm, and has the Curie temperature of greater than 400 K, and the room-temperature ferroelectric material is a ferroelectric material with an extremely low coercive field, a large spontaneous polarization value and a high Curie temperature. Wide application prospects are realized in low-loss nonvolatile memories, sensors, capacitors, optical modulators, electromagnetic nondestructive testing and battery technologies.

Description

Technical Field

[0001] The invention belongs to the technical field of optoelectronic materials, and in particular relates to a new growth method and application of room temperature ferroelectric material with extremely low coercive field and high Curie temperature. Background Art

[0002] Ferroelectric materials have the potential to provide non-volatile storage with low energy consumption and are increasingly being used in various applications such as ferroelectric random access memory, logic memory, using devices such as ferroelectric field effect transistors (FeFETs) and negative capacitance field effect transistors. However, a key challenge is that most current ferroelectric devices require high operating voltages (>1V), limiting their compatibility with low-power operation. Solving this problem would represent a major advance and could pave the way for the integration of ferroelectric materials in next-generation devices beyond conventional CMOS technology to continue Moore's Law. However, the coercive field of most ferroelectric materials is greater than 1 kV / cm, and many inorganic ferroelectric materials have a coercive field of about 10 kV / cm, which increases the difficulty of polarization reversal. The few ferroelectric materials with a coercive field less than 1 kV / cm generally have a low Curie temperature. For example, potassium dihydrogen phosphate (KDP) has a coercive field of only 0.1 kV / cm and a Curie temperature of 123 K, making it unsuitable for device applications at room temperature. Similarly, the coercive field of Rochelle salt is only 0.2 kV / cm, but its Curie temperature is only 297 K, while TGS has a coercive field of 0.9 kV / cm and a Curie temperature of 323 K. IA2MA2Pb3Br10 has a coercive field of 0.8 kV / cm, but a Curie temperature of only 305 K. High Curie temperatures usually correspond to large coercive fields of ferroelectric materials at room temperature. For molecular ferroelectric materials, polarization is usually only easily reversed near their phase transition temperature, which severely limits their applications in electronic devices. Summary of the invention

[0003] Purpose of the invention: In order to solve the technical problems existing in the prior art, the present invention provides a room temperature ferroelectric material with extremely low coercive field, large spontaneous polarization value and high Curie temperature, and its preparation method and application, with a 2.3μC / cm 2 The spontaneous polarization value and coercive field of 0.11kV / cm, and the Curie temperature greater than 400K, have broad application prospects in low-loss non-volatile memory, sensors, capacitors, optical modulators, electromagnetic non-destructive testing and battery technology.

[0004] Technical solution: To achieve the above-mentioned invention purpose, the present invention adopts the following technical solution: a room temperature ferroelectric material with extremely low coercive field, large spontaneous polarization value and high Curie temperature is a zero-dimensional organic-inorganic hybrid perovskite crystal material and has the following chemical formula (C2H8N)4PbBr6.

[0005] Furthermore, the spontaneous polarization value of the room temperature ferroelectric material is 2.3±0.5μC / cm 2 , the coercive field is 0.11±0.02kV / cm, and the ferroelectric Curie temperature is higher than 400K.

[0006] The present invention also provides a method for preparing the room temperature ferroelectric material with extremely low coercive field, large spontaneous polarization value and high Curie temperature, comprising the following steps: S1, adding lead bromide, N,N-dimethylformamide (DMF) and hydrobromic acid aqueous solution into a container, stirring and mixing until a uniform clear solution is obtained; heating and maintaining at 40-90° C. until the liquid is completely evaporated to obtain a white powder; S2, dissolving the white powder obtained in step S1 in N,N-dimethylformamide DMF to form a transparent solution, and performing crystal growth at room temperature to obtain (C2H8N)4PbBr6 crystals.

[0007] Furthermore, in step S1, the molar ratio of lead bromide, N,N-dimethylformamide DMF and hydrobromic acid is 1:8-200:4-200.

[0008] Furthermore, the mass ratio of the white powder to N,N-dimethylformamide DMF in step S2 is 1:5-100.

[0009] The present invention also provides the application of the room temperature ferroelectric material with extremely low coercive field, large spontaneous polarization value and high Curie temperature in low-loss non-volatile memory, sensor, capacitor, optical modulator, electromagnetic non-destructive testing and battery technology.

[0010] Beneficial effects: Compared with the prior art, the present invention has the following advantages: 1. The present invention grows a novel room-temperature ferroelectric (C2H8N)4PbBr6 single crystal for the first time. The dimethylamine ions in the (C2H8N)4PbBr6 crystal are obtained by the reaction of DMF and hydrobromic acid, rather than directly derived from dimethylamine, which increases the solubility of the reaction solution for PbBr2 and promotes the growth of (C2H8N)4PbBr6.

[0011] 2. (C2H8N)4PbBr6 has excellent ferroelectric properties at room temperature, with large spontaneous polarization value, extremely low coercive field and high Curie temperature.

[0012] 3. (C2H8N)4PbBr6 has not only ferroelectricity but also blue fluorescence at room temperature. The combination of fluorescence and ferroelectricity has great potential in future multifunctional optoelectronic applications, including integrated optical sensors. It has broad application prospects in many fields such as low-loss non-volatile memory, sensors, capacitors, optical modulators, electromagnetic non-destructive testing, and battery technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a physical photograph of the (C2H8N)4PbBr6 single crystal obtained in the embodiment of the present invention.

[0014] Figure 2 It is a DSC curve diagram of differential scanning calorimetry of (C2H8N)4PbBr6 single crystal obtained in an embodiment of the present invention.

[0015] Figure 3 : This is a crystal structure view of a (C2H8N)4PbBr6 single crystal obtained in an embodiment of the present invention, where: (a) is along a random direction; (b) is along the a-axis direction. The pink dotted lines represent hydrogen bonds between isolated DMABr.

[0016] Figure 4 The present invention provides a (C2H8N)4PbBr6 single crystal obtained in an embodiment of the present invention. The (C2H8N)4PbBr6 single crystal is measured at room temperature with a current-electric field (IE) signal curve and a polarization-electric field (PE) hysteresis loop, wherein: (a) the current-electric field (IE) signal curve; (b) the polarization-electric field (PE) hysteresis loop.

[0017] Figure 5 This is the UV-visible absorption spectrum of (C2H8N)4PbBr6 obtained in the embodiment of the present invention.

[0018] Figure 6 The optical band gap is calculated from the ultraviolet-visible absorption spectrum of (C2H8N)4PbBr6 obtained in the embodiment of the present invention.

[0019] Figure 7 This is the photoluminescence spectrum of (C2H8N)4PbBr6 obtained in the embodiment of the present invention under 365nm light excitation.

[0020] Figure 8 It is the CIE1931 chromaticity coordinate corresponding to the photoluminescence spectrum of (C2H8N)4PbBr6 under variable temperature conditions obtained in the embodiment of the present invention. DETAILED DESCRIPTION

[0021] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application. Example

[0022] Add 10 mmoles of PbBr2 and 15 ml of 40% aqueous hydrobromic acid to 30 ml of N,N-dimethylformamide. After the mixture was stirred for 30 minutes, a uniform and clear solution was formed. The solution was heated to 60°C and maintained for about a week until all the liquid evaporated and a white powder was obtained. The above white powder was dissolved in 30 ml of DMF and stirred to form a clear solution. The solution was left to evaporate in the air for about two weeks, and finally, several millimeters of (C2H8N)4PbBr6 bulk crystals (DMA4PbBr6) were produced, such as Figure 1 shown.

[0023] like Figure 2 As shown, from the DSC analysis of the (C2H8N)4PbBr6 crystal, it can be observed that no phase change was detected in the temperature range of 100K to 400K.

[0024] from Figure 3 As shown, the crystal space group of (C2H8N)4PbBr6 crystal is Pna21. Figure 4 The IE signal curve and PE hysteresis loop of the surface (C2H8N)4PbBr6 have a spontaneous polarization value of about 2.3μC / cm² and a coercive field of about 0.11kV / cm.

[0025] Figure 5 is the UV-visible absorption spectrum of (C2H8N)4PbBr6. Figure 6 The optical band gap calculated from the UV-visible absorption spectrum of (C2H8N)4PbBr6. Figure 7 The photoluminescence spectrum of (C2H8N)4PbBr6 powder excited by 365 nm light, measured under variable temperature conditions. Figure 8 The CIE 1931 chromaticity coordinates corresponding to the photoluminescence spectrum of (C2H8N)4PbBr6 powder under variable temperature conditions.

[0026] The room temperature ferroelectric material with extremely low coercive field, large spontaneous polarization value and high Curie temperature of the present invention is a mixed organic-inorganic perovskite material (C2H8N)4PbBr6, which has a spontaneous polarization value of about 2.3μC / cm2 and a coercive field of 0.11kV / cm at room temperature, and its Curie temperature is greater than 400K. The (C2H8N)4PbBr6 of the present invention is a zero-dimensional perovskite structure. Different from the typical zero-dimensional perovskite, in (C2H8N)4PbBr6, in addition to the isolated [PbBr6]4-octahedron and the edge-shared [Pb2Br11]7-dimer, there are also isolated DMA...Br pairs. The DMA...Br pairs show polarization along the c-axis direction. By calculating the Hirshfeld dnorm surface and two-dimensional fingerprint map of DMA cation in (C2H8N)4PbBr6, a higher proportion of H…H interactions and larger dnorm values ​​may explain the reason for the ultralow coercive field in (C2H8N)4PbBr6.

[0027] The ultra-low coercive electric field of (C2H8N)4PbBr6 of the present invention provides new possibilities for the design of novel electronic devices by accelerating molecular ferroelectric materials, and has wide application potential in electronic devices.

[0028] The above descriptions are only some embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A room temperature ferroelectric material with extremely low coercive field, large spontaneous polarization value and high Curie temperature, characterized in that: It is a zero-dimensional organic-inorganic hybrid perovskite crystalline material and has the following chemical formula (C2H8N)4PbBr6.

2. The room temperature ferroelectric material with extremely low coercive field, large spontaneous polarization value and high Curie temperature according to claim 1, characterized in that: The spontaneous polarization value of the room temperature ferroelectric material is 2.3±0.5μC / cm 2 , the coercive field is 0.11±0.02kV / cm, and the ferroelectric Curie temperature is higher than 400K.

3. A method for preparing the room temperature ferroelectric material with extremely low coercive field, large spontaneous polarization value and high Curie temperature as claimed in claim 1 or 2, characterized in that The following steps are involved: S1, adding lead bromide, N,N-dimethylformamide (DMF) and hydrobromic acid aqueous solution into a container, stirring and mixing until a uniform clear solution is obtained; heating and maintaining at 40-90° C. until the liquid is completely evaporated to obtain a white powder; S2, dissolving the white powder obtained in step S1 in N,N-dimethylformamide DMF to form a transparent solution, and performing crystal growth at room temperature to obtain (C2H8N)4PbBr6 crystals.

4. The method for preparing the room temperature ferroelectric material with extremely low coercive field, large spontaneous polarization value and high Curie temperature according to claim 3, characterized in that: The molar ratio of lead bromide, N,N-dimethylformamide DMF and hydrobromic acid in step S1 is 1:8-200:4-200.

5. The method for preparing the room temperature ferroelectric material with extremely low coercive field, large spontaneous polarization value and high Curie temperature according to claim 3, characterized in that: The mass ratio of the white powder to N,N-dimethylformamide DMF in step S2 is 1:5-100.

6. Application of the room temperature ferroelectric material with extremely low coercive field, large spontaneous polarization value and high Curie temperature as described in claim 1 or 2 in low-loss non-volatile memory, sensor, capacitor, optical modulator, electromagnetic non-destructive testing and battery technology.

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