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

Abstract

The application discloses a room-temperature ferroelectric material with an extremely low coercive field, a large spontaneous polarization value and a high Curie temperature, a preparation method and application thereof, and is a zero-dimensional organic-inorganic hybrid perovskite crystal material with a chemical formula (C2H8N)4PbBr6, a spontaneous polarization value of 2.3 muC / cm 2 , a coercive field of 0.11 kV / cm, and a Curie temperature greater than 400K, and has a wide application prospect in low-loss nonvolatile memory, sensors, capacitors, optical modulators, electromagnetic nondestructive testing and battery technology.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic materials technology, and in particular relates to a novel method for growing room temperature ferroelectric materials with extremely low coercivity and high Curie temperature, and its application. Background Technology

[0002] Ferroelectric materials possess the potential for low-power, non-volatile storage and are increasingly being used in various applications, such as ferroelectric random access memory, logic memory, and devices utilizing 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 significant advancement and could pave the way for the integration of ferroelectric materials into next-generation devices that go beyond traditional CMOS technologies, thus continuing Moore's Law. However, most ferroelectric materials have coercive fields greater than 1 kV / cm, with many inorganic ferroelectric materials having coercive fields around 10 kV / cm, increasing the difficulty of polarization reversal. A few ferroelectric materials with coercive fields less than 1 kV / cm typically have low Curie temperatures. 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 room-temperature device applications. Similarly, Rochelle salts have a coercive field of only 0.2 kV / cm, but a Curie temperature of 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 typically correspond to large coercive fields in ferroelectric materials at room temperature. For molecular ferroelectric materials, polarization usually reverses easily only near their phase transition temperature, which severely limits their application in electronic devices. Summary of the Invention

[0003] Objective of the Invention: To address the technical problems existing in the prior art, this invention provides a room-temperature ferroelectric material with extremely low coercivity, large spontaneous polarization, and high Curie temperature, as well as its preparation method and applications, exhibiting a temperature of 2.3 μC / cm². 2 With its spontaneous polarization value and coercive field of 0.11 kV / cm, and a Curie temperature greater than 400 K, it has 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 objectives, 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 ± 0.5 μC / cm. 2 The coercive field is 0.11±0.02kV / cm, and the ferroelectric Curie temperature is above 400K.

[0006] This invention also provides a method for preparing the above-mentioned room-temperature ferroelectric material with extremely low coercivity, large spontaneous polarization, and high Curie temperature, comprising the following steps:

[0007] S1, add lead bromide, N,N-dimethylformamide (DMF), and hydrobromic acid aqueous solution to a container and stir until a homogeneous and clear solution is obtained; heat and maintain at 40-90°C until the liquid completely evaporates to obtain a white powder;

[0008] S2, the white powder obtained in step S1 is dissolved in N,N-dimethylformamide (DMF) to form a transparent solution, and crystallization is carried out at room temperature to obtain (C2H8N)4PbBr6 crystals.

[0009] Furthermore, the molar ratio of lead bromide, N,N-dimethylformamide (DMF), and hydrobromic acid in step S1 is 1:8-200:4-200.

[0010] Furthermore, the mass ratio of the white powder to N,N-dimethylformamide (DMF) in step S2 is 1:5-100.

[0011] This invention also provides the application of the aforementioned room-temperature ferroelectric materials with extremely low coercivity, large spontaneous polarization, and high Curie temperature in low-loss non-volatile memories, sensors, capacitors, optical modulators, electromagnetic non-destructive testing, and battery technology.

[0012] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0013] 1. This invention is the first to grow a novel room-temperature ferroelectric single crystal (C2H8N)4PbBr6. The dimethylamine ions in the (C2H8N)4PbBr6 crystal are obtained by the reaction of DMF and hydrobromic acid, rather than directly from dimethylamine. This increases the solubility of PbBr2 in the reaction solution and promotes the growth of (C2H8N)4PbBr6.

[0014] 2. (C2H8N)4PbBr6 exhibits excellent ferroelectric properties at room temperature, with a large spontaneous polarization value, an extremely low coercive field, and a high Curie temperature.

[0015] 3. (C2H8N)4PbBr6 exhibits not only ferroelectricity but also blue fluorescence at room temperature. The combination of fluorescence and ferroelectricity holds great potential for future multifunctional optoelectronic applications, including integrated optical sensors. It also has broad application prospects in low-loss non-volatile memory, sensors, capacitors, optical modulators, electromagnetic non-destructive testing, and battery technology. Attached Figure Description

[0016] Figure 1 This is a photograph of a (C2H8N)4PbBr6 single crystal obtained in an embodiment of the present invention.

[0017] Figure 2 This is a DSC curve of a (C2H8N)4PbBr6 single crystal obtained by differential scanning calorimetry in an embodiment of the present invention.

[0018] Figure 3 This is a crystal structure view of the (C2H8N)4PbBr6 single crystal obtained in an embodiment of the present invention, wherein: (a) is along a random direction; (b) is along the a-axis direction. The pink dashed lines represent hydrogen bonds between isolated DMABr.

[0019] Figure 4 These are the current-electric field (IE) signal curve and polarization-electric field (PE) hysteresis loop of (C2H8N)4PbBr6 single crystal obtained at room temperature in the embodiments of the present invention, wherein: (a) current-electric field (IE) signal curve; (b) polarization-electric field (PE) hysteresis loop.

[0020] Figure 5 This is the UV-Vis absorption spectrum of (C2H8N)4PbBr6 obtained in an embodiment of the present invention.

[0021] Figure 6 The optical band gap is calculated from the UV-Vis absorption spectrum of (C2H8N)4PbBr6 obtained in the embodiments of the present invention.

[0022] Figure 7 The photoluminescence spectrum of (C2H8N)4PbBr6 obtained in this embodiment of the invention under 365nm light excitation is shown.

[0023] Figure 8 The CIE1931 chromaticity coordinates corresponding to the photoluminescence spectrum of (C2H8N)4PbBr6 under varying temperature conditions obtained in the embodiments of the present invention are shown. Detailed Implementation

[0024] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. After reading this invention, any modifications of the invention in various equivalent forms by those skilled in the art will fall within the scope defined by the appended claims. Example

[0025] 10 mmol of PbBr2 and 15 mL of 40% aqueous hydrobromic acid solution were added to 30 mL of N,N-dimethylformamide. The mixture was stirred for 30 minutes to form a homogeneous, clear solution. The solution was heated to 60°C and maintained for approximately one week until all the liquid evaporated, yielding a white powder. This white powder was dissolved in 30 mL of DMF and stirred to form a clear solution. This solution was left to evaporate in air for approximately two weeks, ultimately producing bulk crystals of (C2H8N)4PbBr6 (DMA4PbBr6) several millimeters in size. Figure 1 As shown.

[0026] like Figure 2 As shown, DSC analysis of the (C2H8N)4PbBr6 crystal form revealed no phase transition in the temperature range of 100K to 400K.

[0027] from Figure 3 As shown, the crystallization space group of (C2H8N)4PbBr6 crystal is Pna21. From... Figure 4 The spontaneous polarization value of the surface (C2H8N)4PbBr6 is approximately 2.3 μC / cm², and the coercive field is approximately 0.11 kV / cm.

[0028] Figure 5 shows the UV-Vis absorption spectrum of (C2H8N)4PbBr6. Figure 6 shows the optical band gap calculated from the UV-Vis absorption spectrum of (C2H8N)4PbBr6. Figure 7 shows the photoluminescence spectrum of (C2H8N)4PbBr6 powder excited with 365 nm light, measured under varying temperature conditions. Figure 8 shows the CIE 1931 chromaticity coordinates corresponding to the photoluminescence spectrum of (C2H8N)4PbBr6 powder under varying temperature conditions.

[0029] The room-temperature ferroelectric material of this invention, characterized by extremely low coercivity, large spontaneous polarization, and high Curie temperature, is a hybrid organic-inorganic perovskite material (C2H8N)4PbBr6. It exhibits a spontaneous polarization of approximately 2.3 μC / cm² and a coercivity of 0.11 kV / cm at room temperature, with a Curie temperature greater than 400 K. This invention's (C2H8N)4PbBr6 is a zero-dimensional perovskite structure. Unlike typical zero-dimensional perovskites, (C2H8N)4PbBr6 contains isolated [PbBr6]4-octahedra and edge-shared [Pb2Br11]7-dimers, as well as isolated DMA…Br pairs. These DMA…Br pairs exhibit polarization along the c-axis. By calculating the Hirshfelddnorm surface and two-dimensional fingerprint of the DMA cation in (C2H8N)4PbBr6, the higher proportion of H…H interactions and the larger dnorm value may explain the ultra-low coercive field in (C2H8N)4PbBr6.

[0030] The ultra-low coercive electric field of (C2H8N)4PbBr6 of this invention accelerates the design of novel electronic devices by molecular ferroelectric materials, and has broad application potential in electronic devices.

[0031] The above description is only a partial embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within 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 crystal material with the following chemical formula (C2H8N)4PbBr6, where C2H8N is a dimethylamine cation, and the space group of (C2H8N)4PbBr6 crystal at room temperature is Pna21. It is prepared by the following steps: S1, add lead bromide, N,N-dimethylformamide (DMF), and hydrobromic acid aqueous solution to a container and stir until a homogeneous and clear solution is obtained; heat and maintain at 40-90°C until the liquid completely evaporates to obtain a white powder; S2, the white powder obtained in step S1 is dissolved in N,N-dimethylformamide (DMF) to form a transparent solution, and crystallization is carried out at room temperature to obtain (C2H8N)4PbBr6 crystals; The molar ratio of lead bromide, N,N-dimethylformamide (DMF), and hydrobromic acid in step S1 is 1:8-200:4-200; The mass ratio of the white powder to N,N-dimethylformamide (DMF) in step S2 is 1:5-100.

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

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