KR102271962B1 - Self-Powered Ferroelectric NTC Thermistor Based on Bismuth Titanate and piezoelectric nanogenerator using the same, and The fabricationg method thereof - Google Patents

Abstract

The present invention relates to a thermistor device applied for detecting a temperature resistance. According to an embodiment of the present invention, highly crystalline ferroelectric nanoparticles based on bismuth titanate (Bi_4Ti_3O_12) are implemented, and can provide a flexible ferroelectric high-temperature thermistor with a structure coated on a flexible film. Therefore, the present invention is capable of having an effect that can be applied to a real-time environment temperature warning monitoring system that does not require a battery resource.

Description

Bismuth titanate-based flexible ferroelectric thermistor device and manufacturing method thereof, bismuth titanate-applied composite film-based piezoelectric nanogenerator and manufacturing method thereof, and real-time environmental temperature monitoring system of self-powered structure applying the device {Self-Powered Ferroelectric NTC Thermistor Based on Bismuth Titanate and piezoelectric nanogenerator using the same, and The fabrication method thereof}

The present invention corresponds to a technical field related to a thermistor device applied to temperature resistance sensing.

Temperature monitoring is essential in biomedical, aerospace and automotive applications. A variety of devices have been used to monitor temperature over the past few decades, including thermocouples, resistance temperature detectors (RTDs), integrated circuit sensors (ICs), and thermistors. A temperature measuring device at a specific location is selected based on cost, response time, working range and accuracy. All devices except integrated circuit-based sensors compute a non-linear response to temperature changes. Among these devices, thermistors (ie, temperature-dependent resistance) offer a wide operating temperature range (-50°C to 1000°C), excellent sensitivity and high resistivity, low cost and fast response time with small size.

In general, thermistors fall into two categories: positive temperature coefficient resistors used for overcurrent limiters (i.e. temperature is directly proportional to resistance) and negative temperature coefficient (NTC) resistors used for temperature sensing (temperature is inversely proportional to resistance). classified as

NTC thermistors were commercialized in 1930 and have become more widely used in a wide range of applications over the past few decades. The projected compound annual growth rate of approximately 4% for thermistor use over the period 2017-2222 equates to a market value of approximately $1 billion. However, these predictions are realized according to many parameters, including availability of high-performance materials, wide operating temperature range, low manufacturing cost, good stability and long service life.

A negative temperature coefficient (NTC) thermistor is a thermistor that has a negative temperature coefficient and continuously changes electrical resistance, and is used as a temperature sensor by using this characteristic. In particular, in the case of automobiles and electric vehicles that must operate stably in the range of -45°C to 120°C, a temperature sensor using an NTC thermistor is used to measure the temperature. In addition, battery charging is controlled according to the measured temperature to protect automobiles and accessories of electric vehicles.

Currently, thermistors are available in spinel (NiMn ₂ O ₄ , MnFe ₂ O ₄ ), perovskites (CaTiO ₃ , BaBiO ₃ ), carbon materials (rGO, CNT, graphene), polymers (PVDF-TrFE, PEDOT). : PSS) and a polymer/carbon material composite.

Commercial spinel-based NTCs, although common, _{have many disadvantages, including low resistivity, high electron activation energy (E a} ), low thermal stability, and unsuitability for high-temperature applications due to structural distortion (eg degree of inversion). In contrast, polymer composite-based NTC thermistors are limited by lower operating temperatures.

3000 K (CaTiO₃)이며, 상용 이용의 적합성을 위해 개선되어야 할 필요가 있다.Recently, ABO ₃ perovskite has received great attention due to its high change in resistance to temperature, which is much greater than that of spinel materials, and the reported thermal sensitivity (β) of perovskite is

3000 K (CaTiO ₃ ) and needs to be improved for suitability for commercial use.

Most high temperature NTC thermistors are used in inrush current limiters (electric power supply industry and motor drives) as well as exhaust gas sensors/catalytic converters as pyrometer gauges in vehicle internal combustion engines. There is great research interest in recognizing alternative novel perovskite materials with improved thermal sensitivity (β) over spinel carbon materials.

Current manufacturing methods of thermistor devices (rigid and flexible) require expensive equipment and special atmospheric conditions. The sputtering and ceramic tape casting used to fabricate robust structures require high vacuum, high power and temperature atmospheres.

Flexible films can be manufactured using gravure, inkjet and screen printing techniques, but require expensive cartridges. There is a need to develop a cost-effective and environmentally friendly method for manufacturing highly flexible perovskite thermistors suitable for operation over a wide temperature range.

Thermistors can be operated continuously from an external power source or from complex battery energy. However, this increases the size and weight of the thermistor, limits its lifetime, and requires complex wiring. Accordingly, the need for a structure that can solve the problem of external power or battery is increasing.

Korean Patent No. 10-1504429

The present invention has been devised to solve the above problems, and an object of the present invention is _{to implement highly crystalline ferroelectric nanoparticles based on bismuth titanate (Bi 4} Ti ₃ O ₁₂ ), and to form a flexible film on the Provides a flexible ferroelectric high-temperature thermistor with a coated structure, and a piezoelectric nanogenerator (BPCF-PNG) by applying a composite film using PVDF and nanoparticles based on _{bismuth titanate (Bi 4} Ti ₃ O _{12 )} The goal is to provide a technology that can be applied to a real-time environmental temperature warning monitoring system that does not require battery resources, through which it can generate the power required to drive a high-temperature thermistor by itself.

As a means for solving the above problems, in an embodiment of the present invention, a first step of synthesizing a mixture by mixing a precursor material and a solvent to form a _{bismuth titanate (Bi 4} Ti ₃ O _{12 );}

a second step of calcining the mixture to form bismuth titanate nanoparticles (Bi ₄ Ti ₃ O _{12 NPs);}

a third step of forming the bismuth titanate nanoparticles into a slurry-type paste and coating the bismuth titanate nanoparticles on a flexible Kapton film; and

a fourth step of implementing an electrode and a terminal connected to the electrode on the flexible Kapton film;

containing,

To provide a method for manufacturing a bismuth titanate-based flexible ferroelectric thermistor device.

Furthermore, it is possible to provide a bismuth titanate-based flexible ferroelectric thermistor device including a structure in which _{highly crystalline ferroelectric Bi 4} Ti ₃ O ₁₂ nanoparticles according to the above-described manufacturing method are brush-coated on a flexible Kapton film. let it be

In addition, according to another embodiment of the present invention, a) bismuth titanate (Bi ₄ Ti ₃ O ₁₂ ) is mixed with a solvent to synthesize a sol-gel material;

b) pulverizing the sol-gel material to form bismuth titanate nanoparticles (Bi ₄ Ti ₃ O ₁₂ NPs);

c) drying a mixture obtained by adding the bismuth titanate nanoparticles (Bi ₄ Ti ₃ O _{12 NPs) to a PVDF solution to form a composite film (Bi 4} Ti ₃ O ₁₂ NPs/PVDF composite films: BPCF);

d) cutting the composite film to form a unit composite film, and laminating a copper (Cu) film on both surfaces of the unit composite film;

containing,

To provide a method for manufacturing a bismuth titanate-applied composite film-based piezoelectric nanogenerator.

Furthermore, it is possible to provide a bismuth titanate applied composite film-based piezoelectric nanogenerator manufactured by the manufacturing method.

In addition, according to another embodiment of the present invention, a sensing unit for sensing temperature-related information;

a control unit including an interface for collecting and processing information transmitted from the sensing unit and transmitting a control signal to an external terminal;

a monitoring unit that transmits a light-emitting or audio signal set according to a control signal of the control unit;

and a display unit for displaying the operation status of the sensing unit, the control unit, and the monitoring unit.

The sensing unit is

A bismuth titanate-based flexible ferroelectric thermistor device comprising a structure in which highly crystalline ferroelectric Bi4Ti3O12 nanoparticles are brush-coated on a flexible Kapton film; and

_{A composite film (Bi 4} Ti ₃ O ₁₂ NPs/PVDF composite films: BPCF) prepared by drying a mixture in which the bismuth titanate nanoparticles (Bi ₄ Ti ₃ O _{12 NPs) are added to a PVDF solution;}

The composite film is cut to form a unit composite film, and a composite film-based piezoelectric nanogenerator having a structure in which a copper (Cu) film is laminated on both sides of the unit composite film-based piezoelectric nanogenerator; is implemented in a parallel-connected structure,

It is possible to provide a real-time environmental temperature monitoring system of a self-generation structure.

According to an embodiment of the present invention, it is possible to realize highly crystalline ferroelectric nanoparticles based on bismuth titanate (Bi4Ti3O12) and to manufacture a flexible ferroelectric high-temperature thermistor with a structure coated on a flexible film. .

The ductile ferroelectric high temperature thermistor manufactured in this way has the advantages of high thermal sensitivity (β(100/260) = 6515 K) and a wide operating temperature range (25°C to 260°C).

In addition, according to another embodiment of the present invention, a piezoelectric nanogenerator (BPCF-PNG) is manufactured by applying a composite film using PVDF and nanoparticles based on _{bismuth titanate (Bi 4} Ti ₃ O _{12 ).} Through this, the power required to drive the high-temperature thermistor can be generated by itself, which has the effect of being applied to a real-time environmental temperature warning monitoring system that does not require battery resources.

1 to 5 are diagrams illustrating a manufacturing process and an experimental result according to an embodiment and another embodiment of the present invention.
6 is a conceptual diagram of a synthesis process showing the sol-gel synthesis _{of Bi 4} Ti ₃ O _{12 NPs.} 7 is a manufacturing process conceptual diagram illustrating the preparation of PVDF and BPCFs. 8 shows an energy band diagram for bias voltage dependent conductivity of a symmetrical MSM structure. 9 provides a temperature-dependent IV measurement of FHTT at fixed bias. 10 shows PE loop measurements of _{Bi 4} Ti ₃ O ₁₂ pellets under different electric field/frequency conditions. 11 provides structural, functional and ferroelectric analysis of BPCF. Figure 12 provides the energy harvesting analysis and mechanism of action of BPCF-PNGs. Figure 13 provides an analysis of BPCF-PNG (25 wt %) and capacitor charge. 14 depicts harnessing biomechanical energy using BPCF-PNG (25 wt %). 15 is a morphological analysis of a _{Bi 4} Ti ₃ O _{12 film.} 16 shows a self-powered thermistor made from a commercial NTC thermistor. 17 shows a commercial NTC-based early warning/monitoring system.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art can easily carry out the present invention. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. Throughout the specification, like reference numerals are assigned to similar parts.

1. Manufacturing method of bismuth titanate-based flexible ferroelectric thermistor device

In an embodiment of the present invention, as a method for manufacturing a bismuth titanate-based flexible ferroelectric thermistor device, bismuth titanate (Bi ₄ Ti ₃ O ₁₂ ) is mixed with a solvent to synthesize a sol-gel material; Step 2 of pulverizing the sol-gel material to form bismuth titanate nanoparticles (Bi ₄ Ti ₃ O ₁₂ NPs), forming the bismuth titanate nanoparticles into a slurry paste, and then coating the bismuth titanate nanoparticles on a flexible Kapton film Step 3 and Step 4 of implementing an electrode and a terminal connected to the electrode on the flexible Kapton film may be included.

In this case, the first step is

1-1) Bi(NO ₃ ) ₃ ·5H ₂ O, and Ti(OC ₄ H ₉ ) ₄ Adding and stirring a dimethylformamide (C ₃ H ₇ NO, DMF) solvent, and 1-2) the above 1 -1) adding polyvinylpyrrolidone [(C ₆ H ₉ NO) n, PVP] to the solution and stirring to implement it in a sol form, 1-3) converting the resulting sol into a gel form, 80 ° C. It may be configured including the step of implementing in a flake type by heat treatment for 24 hours.

In addition, in the case of the second step, it is possible to have nanoparticles of particles through the two-step pulverization process.

Furthermore, in step 3, 3-1) the bismuth titanate nanoparticles (Bi ₄ Ti ₃ O ₁₂ NPs) are mixed with a solvent of N-methyl-2-pyrrolidone to uniformly It may be configured to include a step of implementing a slurry-type paste, 3-2) coating the slurry-type paste on a flexible Kapton film using a brush, and then drying the slurry-type paste at 70° C. for 30 minutes.

In step 4, 4-1) after step 3-2), cutting the flexible Kapton film to implement a unit film, 4-2) coating silver (Ag) paste on both ends of the unit film to implement an electrode terminal, and 4-3) forming a copper (Cu) lead on the electrode terminal.

Examples of the above process steps will be described in detail below.

The basic materials used in the preparation of ferroelectric bismuth titanate nanoparticles applied in a number of embodiments of the present invention are as follows.

bismuth nitric acid pentahydrate [Bi(NO ₃ ) ₃ .5H ₂ O as bismuth source], tetrabutyl titanate [(Ti(OC ₄ H ₉ ) ₄ ) as titanium source], dimethylformamide (C ₃ H ₇ NO, DMF), polyvinylpyrrolidone [(C ₆ H ₉ NO) n, PVP], and polyvinylidene fluoride (-(C ₂ H ₂ F ₂ ) _n- , PVDF) are used in the practice of the present invention described below. It was used to fabricate high-temperature thermistors in the example, composite films for energy harvesting, and ferroelectric NPs for self-actuated systems.

(1) sol-gel synthesis process of bismuth titanate nanoparticles

Bi(NO ₃ ) ₃ ·5H ₂ O (7.75 g), and Ti(OC ₄ H ₉ ) ₄ (4.125 ml) _{were added to a solvent of Dimethylformamide (C 3} H ₇ NO, DMF) and stirred for 30 minutes to obtain a stable solution got

Then, polyvinylpyrrolidone [(C ₆ H ₉ NO)n, PVP] (12.5 g) was added to this solution, which was further stirred for 16 hours. Here, PVP serves to prevent agglomeration and also to reduce and control the shape of crystals.

Thereafter, the resulting sol was converted into a gel form and transformed into dry and brittle macro-sized flakes by heat treatment at 80° C. for 24 hours.

The flakes were pulverized into small particles using mortar and pestle, then heated in a tubular furnace at 700° C. for 2 hours and _{further pulverized to obtain the desired Bi 4} Ti ₃ O ₁₂ NPs (Fig. 6). .

The structure, surface morphology, function and electrical properties of the synthesized Bi ₄ Ti ₃ O _{12 NPs were tested using various techniques.} Bismuth titanate nanoparticles (Bi ₄ Ti ₃ O ₁₂ NPs) synthesized in this process were also used to convert negative temperature thermist (NTC) and mechanical energy into electrical energy into power sensors and low power consumption devices.

(2) Fabrication of a flexible ferroelectric thermistor device using brush coating technology

The sol-gel-derived highly crystalline ferroelectric Bi ₄ Ti ₃ O ₁₂ NPs prepared in the process of (1) described above were mixed with an N-methyl-2-pyrrolidone solvent until a uniform slurry-like paste was formed.

This slurry was coated on a flexible Kapton film (5 x 5 cm ² ) using a commercial brush and then dried in an oven at 70° C. for 30 minutes.

A flexible ferroelectric thermistor device (0.2 × 0.25 × 0.002 cm ³ ) made of a dried flexible film was cut to the required size and coated with silver (Ag) paste at both ends of the film with a gap of 0.12 cm.

The thermistor device was realized by attaching current collecting copper (Cu) leads to _{both sides of the Ag/Bi 4} Ti ₃ O ₁₂ /Ag device structure.

A temperature-dependent current-voltage (I-V) study of the thermistor device was performed in a silicone oil bath heated on a hot plate at 25-260° C. while monitoring the temperature of the oil with a thermometer. Silicone oil was chosen because of its high stability and good heat transfer at high temperatures.

2. Fabrication of flexible piezoelectric Bi ₄ Ti ₃ O ₁₂ NPs/PVDF composite film and piezoelectric generator

As another embodiment of the present invention, a bismuth titanate applied composite film-based piezoelectric nanogenerator is manufactured so that it can be applied to a device performing a self-generation function.

As a method for preparing this, a) bismuth titanate (Bi ₄ Ti ₃ O ₁₂ ) is mixed with a solvent to synthesize a sol-gel material;

b) pulverizing the sol-gel material to form bismuth titanate nanoparticles (Bi ₄ Ti ₃ O ₁₂ NPs);

c) drying the mixture obtained by adding the bismuth titanate nanoparticles (Bi ₄ Ti ₃ O _{12 NPs) to the PVDF solution to form a composite film (Bi 4} Ti ₃ O ₁₂ NPs/PVDF composite films: BPCF);

d) cutting the composite film to form a unit composite film, and laminating a copper (Cu) film on both surfaces of the unit composite film.

(1) a flexible piezoelectric Bi ₄ Ti ₃ O Preparation of ₁₂ NPs / PVDF composite film _{(Fabrication of flexible piezoelectric Bi 4 Ti} 3 O 12 NPs / PVDF composite films)

In this process, a composite film applied with _{Bi 4} Ti ₃ O _{12 NPs and PVDF (Bi 4} Ti ₃ O ₁₂ NPs/PVDF composite films: hereinafter, it is defined as 'BPCF' or 'composite film') is manufactured. process is carried out.

As an example, films of pure PVDF and BPCF in weight ratios of 5, 10, 15, 20 and 25 wt % were prepared by a cost-effective large-scale solution-casting technique (see FIG. 7 ).

Electroactive β-phase PVDF film (heated overnight at 70°C) was a transparent PVDF prepared by dissolving α-phase PVDF powder (1 g) in DMF solvent (10 mL) with sonication (30% amplitude, 750 watts) for 1 h. prepared from solution.

_{Bi 4} Ti ₃ O ₁₂ NPs (0.5 g) was added to the transparent PVDF solution and sonicated for about 30 minutes to prepare a BPCF solution (5 wt%).

The final composite solution was transferred to a glass Petri dish and stored in an oven at 70° C. for 12 hours to evaporate the excess solvent and dry the composite film (BPCF).

10, 15, 20, 25 and 30 wt% of BPCFs were prepared in a similar manner, and _{the increase of Bi 4} Ti ₃ O ₁₂ NPs loaded into PVDF changed the smooth glass surface of PVDF to a rough and opaque surface.

(2) Fabrication of flexible BPCF piezoelectric nanogenerator

The process of manufacturing the piezoelectric nanogenerator by applying the composite film (BPCF) prepared in the above-described process is as follows.

Implement a laminate of the structure as shown in Figure 3a, but in a specific embodiment, BPCFs (0, 5, 10, 15, 20, 25 and 30 wt% ^{) are cut into squares (3 x 3 cm 2} ) and the device It was sandwiched between two flexible Cu foils (2 x 2 cm ² ) serving as the upper/lower electrodes of the (Fig. 3a).

Charge carriers generated in relation to mechanical force on the device were obtained through copper wires (diameter = 0.1 mm) attached by silver paste on two Cu electrodes.

Successful fabrication of flexible BPCF-PNG was achieved by hot pressing for about 1 hour an insulating PDMS polymer coated on the top Cu electrode and a Kapton film attached to the bottom Cu electrode of the Cu/BPCF/Cu device structure.

The packaging layer helps to reduce environmental interferences such as humidity, unwanted temperature and gas effects on the output of the BPCF-PNG device. All BPCF-PNGs were electrically polarized (ie, the electrical dipoles were aligned in one preferred orientation) by applying 7 kV for 12 h at room temperature.

In the description of the present invention, thereafter,

Bi ₄ Ti ₃ O ₁₂ NPs/PVDF composite films (Bi ₄ Ti ₃ O ₁₂ NPs/PVDF composite films:BPCF)

Bi ₄ Ti ₃ O ₁₂ NPs/PVDF Composite Film-Based Piezoelectric Nanogenerator (BPCF-PNG)

The abbreviation with the definition of the term is used in parallel.

3. Design of a self-powered temperature monitoring system/ real-time emergency alert system

As shown in Figure 4a, FHTT (flexible ferroelectric high-temperature thermistors (FHTTs) and Bi ₄ Ti ₃ O ₁₂ NPs/PVDF composite film-based piezoelectric nano By applying a generator (BPCF-PNG), it is possible to implement a self-powered temperature monitoring system/real-time emergency alarm system.

Specifically, a real-time environmental temperature monitoring system of a self-generation structure in another embodiment of the present invention includes: a sensing unit for sensing temperature-related information; a control unit including an interface for collecting and processing information transmitted from the sensing unit and transmitting a control signal to an external terminal; a monitoring unit that transmits a light-emitting or audio signal set according to a control signal of the control unit; and a display unit for displaying the operation status of the sensing unit, the control unit, and the monitoring unit.

In particular, the sensing unit includes a bismuth titanate-based flexible ferroelectric thermistor device including a structure in which _{highly crystalline ferroelectric Bi 4} Ti ₃ O _{12 nanoparticles are brush-coated on a flexible Kapton film and a PVDF solution.} A composite film (Bi4Ti3O12 NPs/PVDF composite films: BPCF) prepared by drying a mixture containing bismuth titanate nanoparticles (Bi4Ti3O12 NPs) and the composite film are cut to form a unit composite film, and the A composite film-based piezoelectric nanogenerator having a structure in which copper (Cu) films are laminated on both sides is implemented in a parallel-connected structure, and can be implemented as a real-time environmental temperature monitoring system of a self-powered structure.

As an example, a sensing unit implemented in a parallel-connected structure between a BPCF-PNG (composite piezoelectric nanogenerator) and FHTT (flexible ferroelectric high-temperature thermistors (FHTTs)) is provided. In particular, a temperature monitoring system/ It was connected to a pre-programmed Arduino circuit (board model UNO R3) to build a real-time emergency alarm system, in which the following two operating conditions are programmable, and the ambient temperature of the FHTT is 40°C. The system can be systematized to implement an alarm by dividing it into a danger signal that lights up with a red LED and sounds an alarm when it exceeds, and a safety signal that turns on a green LED when the ambient temperature is lower than 40℃.

According to the above embodiment, _{highly crystalline ferroelectric nanoparticles based on bismuth titanate (Bi 4} Ti ₃ O ₁₂ ) are implemented, and a flexible ferroelectric high temperature thermistor is manufactured with a structure coated on a flexible film, The fabricated flexible ferroelectric high temperature thermistor has the advantages of high thermal sensitivity (β(100/260) = 6515 K) and a wide operating temperature range (25° C. to 260° C.).

In addition, by applying a composite film using PVDF and nanoparticles based on bismuth titanate (Bi ₄ Ti ₃ O ₁₂ ), a piezoelectric nanogenerator (BPCF-PNG) can be manufactured, and through this It can be made to generate the power required to drive the mist itself, and through this, it can be applied to a real-time environmental temperature warning monitoring system that does not require battery resources.

Hereinafter, the experimental results for the characteristics of the components constituting the structure of the flexible ferroelectric high-temperature thermistor and the piezoelectric generator according to the embodiment of the present invention described above are based on Figs. 1 to 5, and Figs. Reference descriptions for principles and term definitions will be described with reference to FIGS. 6 to 17 .

1 is a view showing a cost-effective brush-coating process used to manufacture flexible ferroelectric high-temperature thermistors (hereinafter, 'FHTT') and a device layer and a characteristic test result.

Figure 1 (a) Schematic diagram and field emission scanning electron microscopy image of a flexible thermistor. (b) X-ray diffraction diagram including insets showing the surface morphology and energy-dispersive analysis mapping of sol-gel-derived Bi ₄ Ti ₃ O _{12 nanoparticles (NPs).} (c) Raman spectrum of _{Bi 4} Ti ₃ O _{12 NPs.} (d,e) Temperature-dependent current-voltage study of thermistors at bias voltages of ±10 V and 0 to 100 V. (f,g) Temperature-dependent resistance of thermistor and Arrhenius plots. (h) An estimated energy band model of the operating mechanism of a flexible ferroelectric thermistor as a function of constant bias voltage.

The right side of Fig. 1a shows the surface morphology of the FHTT device at the 2 mm scale and shows the uniform coating _{of Bi 4} Ti ₃ O _{12 NPs on the flexible Kapton surface.} Good electrical contact was ensured by Ag electrodes on the surface of the ferroelectric material. Before preparing FHTT, the structural, morphological and elemental composition and optical phonon mode were investigated by XRD, Raman spectroscopy, FE-SEM and EDS. The XRD peak of Bi ₄ Ti ₃ O ₁₂ NPs is consistent with the reference pattern (JCPDS 01-073-2181); The (117) peak located at 30° confirmed an orthorhombic phase.

The figure of FIG. 1b shows Bi ₄ Ti ₃ O ₁₂ NPs of irregular shape, and the corresponding EDS mapping confirmed the existence of all essential elements.

Figure 1c shows the Raman spectrum and active light phonon mode _{of Bi 4} Ti ₃ O _{12 NPs, i.e. A 1g} (560, 613 and 848 cm ^-1 ), B1g (357, 449 cm ^-1 ) and B2g + B3g ( 229, 269 and 536 cm ⁻¹ ) modes. The peaks at 117 cm ⁻¹ were assigned to the Bi-O vibration, whereas ^{the peaks at 229 and 269 cm −1} were assigned to the O-Ti-O stretching mode. The peaks at 848 and 613 cm ⁻¹ were assigned to symmetric and asymmetric Ti-O oscillations, respectively. Stimulation of the TiO ₆ octahedron at room temperature and Bi ₄ Ti ₃ O _{12 NPs induces ferroelectricity.} The XRD and Raman patterns were consistent with the presence of orthorhombic (space group Fmmm) of _{ferroelectric Bi 4} Ti ₃ O _{12 NPs at room temperature.}

3.5 eV)을 2개의 Ag-금속 전극들(작동 기능: 4.26 eV) 사이에 대칭적으로 개재시켜 평면 대칭 금속-반도체-금속 (MSM) 구조를 형성함으로써 제조되었다. FHTT is a p-type Bi ₄ Ti ₃ O ₁₂ NPs polycrystalline film (Eg

3.5 eV) was symmetrically interposed between two Ag-metal electrodes (working function: 4.26 eV) to form a planar symmetric metal-semiconductor-metal (MSM) structure.

The bias voltage dependent IV curve as a function of temperature (Fig. 1(d,e)) shows a linear change, indicating that it has a non-zero current at V = 0 V due to the ferroelectric effect of _{Bi 4} Ti ₃ O _{12 NPs.}

The characteristic of the IV curve is that an Ohmic contact is formed between _{the Ag-Bi 4} Ti ₃ O ₁₂ interface due to the higher Fermi energy level of the metal than that _{of the ferroelectric p-type material (F Metal} > F _{Material ), resulting in nanoampere} - Generates scale current. The low current at room temperature may be due to the mobility of trapped free charge carriers and the high intrinsic impedance properties of the insulator.

Referring to for conceptual explanations with respect to FIG. 1 , FIG. 8 illustrates a charge transfer process for an applied bias voltage, illustrated through an energy band diagram of an MSM structure, and is described in a support information (SI) file.

The current conduction of the FHTT depends on the bias voltage-dependent diffusion/drift charge carrier mobility. The magnitude and failure of the current (rapid spikes in current) depend on the type of electrode/actuation function, the formation of metal-insulator interface regions, electronic failure (electron or hole injection in the insulator) and thermal failure (by thermal mechanisms) conditions.

The temperature-dependent current (I)-voltage (V) curve of the FHTT according to the bias voltage ±100V is shown in Fig. 9, and the enlarged data (±10V) is shown in Fig. 1D. Here, the generated current does not pass through the origin (0.018 nA, 0 V and 0.74 nA at room temperature, 0 V at 260 °C) because it is embedded in the _{Bi 4} Ti ₃ O ₁₂ ferroelectric material as a function of temperature at constant bias voltage.

Here, the increase in current is mainly due to the temperature-dependent conduction process of _{Bi 4} Ti ₃ O _{12 .} The possibility of hopping in Bi ions occurs through the (Bi ₂ O ₂ ) ^{2+ layer with a Bi 3+} to Bi ^{4+ hopping mechanism.} Similarly, electronic conductivity arises due to polaron hopping between ^{Ti 4+} and Ti ^{3+ ions.}

Oxide ion conduction initiated by Bi deficiency and oxygen vacancies generated in material processing can be described using the Krøger-Vink equation (SI). In addition, ^{it has been proposed that the high polarizability of Bi 3+ ions with 6s 2} lone-pair electrons and weak Bi-O bonds helps the transport of oxygen ions by providing a pathway for a low diffusion barrier. However, the prepared FHTT IV response showed no signs of electrical and thermal failure. It is suggested that the FHTT device can operate above 100V and above 260°C. The current curve through the negative x-axis (-35V) at room temperature and at this value shifts towards the zero voltage point (-0.6V) whenever the applied temperature increased from room temperature to 260°C shows a decrease in the built-in electric field ( 1d). The active ferroelectric material resistance is evaluated by a temperature-dependent IV curve at a positive voltage of 0 to 100 V and the corresponding Arrhenius plot shown in Fig. 1(eg).

Here, the current value changed from 0.0594 nA to 93.113 nA whenever the temperature is changed from room temperature to 260° C. confirms that the Bi ₄ Ti ₃ O ₁₂ material has a negative temperature coefficient (NTC) characteristic. Figure 1f shows that the calculated resistance is 2.088 TΩ at room temperature, reduced to 1.078 GΩ at a maximum operating temperature of 260°C. The equations mentioned below represent the nonlinear change in resistance versus temperature.

exp (

R =

exp(

는 초기온도에서의 저항이고, 그리고 β는 서미스터 상수이다. 도 1g에서 유도된 β값(β_(100/260) = 6515 K)은 일반적인 반도체성 금속산화물-기반 서미스터 값( 5000 K)보다 높다. where R is the resistance at temperature T,

is the resistance at the initial temperature, and β is the thermistor constant. The β value (β _(100/260) = 6515 K) derived from Fig. 1g is higher than the typical semiconducting metal oxide-based thermistor value (5000 K).

The detailed calculation of the β value will be described in the description of the term definitions to be described later.

{Table 1: FHTT data sheet]

The proposed FHTT has a high β value with a wide operating temperature. In addition, the accuracy of the NTC behavior, FHTT, was analyzed by the Steinhart-Hart (S-H) empirical equation. The values of the S-H coefficients are listed in Table 1 and their calculations are described in the Calculation Principle Explained Part below.

The temperature coefficient of resistance (TCR, α) is a value of -5.76 %/K at 25°C, and Ve represents the NTC behavior of FHTT. The dissipation constant δ was 3.95744 e ^-5 (mW/C). To avoid thermistor measurement errors caused by self-heating, the value of δ should be low, which varies greatly depending on the thermistor environment. All detailed FHTT datasheet calculations are given in SI.

Finally, the thermistor sensing performance is compared with other materials presented in Table 2.

및 β값의 곱에 의해 평가된 FHTT의 활성화 에너지(E_a)는 FHTT 장치에서 온도 의존적 자유전하 캐리어의 생성으로 인해 0.44eV이다. 비선형 아레니우스 플롯은 E_a가 온도 의존적 파라미터를 나타내며 FHTT의 층들 사이에서 전하 캐리어의 호핑을 위한 에너지를 반영한다.As mentioned, there is a linear drop in resistance from room temperature to 120° C. (region 1), after which a non-linear change in resistance was observed as shown in Fig. 1g.

and β values, the activation energy (E _a ) of FHTT is 0.44 eV due to the generation of temperature-dependent free charge carriers in the FHTT device. The nonlinear Arrhenius plot shows that E _a represents a temperature-dependent parameter and reflects the energy for hopping of charge carriers between the layers of the FHTT.

{Table 2: Comparison of proposed FHTT parameters (thermal constant (β) and operating temperature range) with reported commercial NTC thermistors.}

The working principle of FHTT was explored by the energy band model mechanism through temperature-dependent hopping of electrons between interfaces.

Estimated circuit diagram of FHTT at four different temperatures (25, 100, 180 and 260° C.) shown in FIG. 1h.

FHTT provides low current values (0.0594 nA @ 100V) at room temperature due to the presence of a high resistance (ρ 6.96207E9 Ω.cm) barrier between _{metallic Bi 4} Ti ₃ O _{12 NPs interfaces.} In addition, the high resistance is due to the random orientation of the electric dipole, which in turn reduced the cumulative spontaneous polarization of the _{ferroelectric Bi 4} Ti ₃ O _{12 NPs.} The generated currents of the FHTT device were then 0.0594 nA to 0.9 nA (ρ 5.62E8 Ω cm) and 10.76 nA (ρ 3.34581E7 Ω cm) and 10.76 nA (ρ 3.34581E7 Ω cm) at the same bias voltage 100 V as a function of various temperatures, such as 100° C. increases to

Higher temperature improved the mobility of the charge carriers (improved conductivity), which made them more easily transportable to overcome the barrier height and provided improved polarization.

260℃)를 더 높이면 도 1h(iv)에 도시한 바와 같이, 금속 Bi₄Ti₃O₁₂ NPs 인터페이스 층의 전도 특성이 개선되어 동일한 바이어스 전압에서 93.113nA (ρ3.59552E6 Ω.cm)의 높은 전류값을 제공한다.Reduction of the potential barrier naturally formed between metal/Bi ₄ Ti ₃ O ₁₂ NPs leads to an improved number of free charge carriers by proper alignment of electric dipoles in ferroelectric materials, as shown in Fig. 1h(ii, iii). indicates that FHTT application temperature (

260° C.), as shown in FIG. 1h(iv), _{the conductive properties of the metallic Bi 4} Ti ₃ O ₁₂ NPs interface layer were improved, resulting in a high current of 93.113nA (ρ3.59552E6 Ω.cm) at the same bias voltage. provides a value.

The trend of the temperature-dependent current profile indicates that the underlying mechanism behind the resistance reduction is due to the enhanced polarization of the FHTT. In this case, the maximum attained operating temperature of the FHTT is 260° C. due to the boiling limit of the silicone oil bath.

FIG. 2 shows the evaluation of the ferroelectric properties of _{poled/non-poled Bi 4} Ti ₃ O ₁₂ NPs pellets by characterizing the electric field/frequency-dependent PE loop.

Figure 2. (a) Schematic of electric field-dependent polarization-electric field (PE) loop measurements and directional electric dipoles of unpolarized _{Bi 4} Ti ₃ O ₁₂ pellets at a constant frequency of 1 Hz. (b) Schematic of frequency-dependent PE loop measurements and directional electric dipoles of unpolarized samples in a constant electric field of 50 kV. (c) Comparison of PE loops of poled/non-poled pellets at 50 kV, 1 Hz. (d) Electric field-dependent PE loop of a poled sample at 1 Hz. (e) Comparison of coercive field (Ec) and remanent polarization (P _r ) as a function of operating frequency/electric field (f) Current of poled Bi ₄ Ti ₃ O ₁₂ pellets at 120 kV bias voltage ( I) - voltage (V) measurement. (g) Leakage current analysis _{of Bi 4} Ti ₃ O ₁₂ pellets as a function of E over 1,000 ms. (h) Polarization fatigue analysis of Bi ₄ Ti ₃ O ₁₂ ^{pellets over 10 10 cycles.} (i,j) Frequency-dependent (10 ¹ -10 ⁶ Hz) dielectric constant, loss, and AC conductivity of the sample. The inset image shows the surface morphology of the pellet.

The PE loop region, remanent polarization (P _r ) and coercive field (E _c ) of the non-poled sample are the applied electric fields (10, 25 and 50 KV) at constant frequency (@ 1 Hz). is increased by increasing At 10 KV @ 1Hz electric field, _{P r} : E _c ^{of 0.12 μC/cm 2} : 4.9 KV/cm ^{increased to 0.45 μC/cm 2} : 22.47 KV/cm at 50 KV @ 1 Hz.

The improved polarization switching with respect to the electric field schematically shown in Fig. 2a shows the ferroelectricity _{of Bi 4} Ti ₃ O _{12 NPs.} Since the dipole rotates 180° with opposite sign under the same electric field strength, the figure is based on one side of the PE loop data.

The effect of frequency changes in the PE loop was also measured. The corresponding switching P mechanism is schematically shown in Fig. 2b. Here, the P _r : E _c value was 0.322 μC/cm ^{2 : 19.40 KV/cm, and it significantly increased to 0.068 μC/cm 2} : 6 KV/cm with every increase of the operating frequency (in a 50 KV electric field) from 2 to 10 Hz. decreased. At low frequencies (1 Hz), the available mobile free charge can contribute to the overall polarization, and the dipole alignment provides high polarization as it has sufficient time to align in the direction of the applied electric field.

However, at 2, 4 and 10 Hz, the hysteresis loop gap begins to decrease and becomes elliptical due to reduced dipole switching for a constant applied electric field. This indicates that the hysteresis loop shape is based on the time-period of the excitation signal in the applied electric field and the dipole switching time.

Here, the maximum number of electric dipoles switching in the desired direction at low frequencies resulted in a _{high P r .} P _r decreased as the applied frequency of E increased due to partial switching of the electric dipole in the sample. This is in good agreement with the Weiss mean field model.

Electrical poling (7 KV/12 h at room temperature) is used to enhance the permanent polarization of the prepared sample. A poled/un-poled PE loop is shown in FIGS. 2C and 10A . Here, the folding back (poled) samples were higher ratio folds (un-poled) (0.45 μC / cm 2) and more than double the P _r of 1.08 μC / cm ² as compared to in the 1 KHz and 50 KV.

The synthesized samples are maintained even at higher electric fields such as 0 to 120 KV with multiple frequencies (Fig. and S5 (be)). _{The polled sample shows a high P r} = 6 μC/cm ² for the used electric field 120 KV @ 1 Hz, a multiple-fold increase over the reported paper.

Figure 2e shows the linearly increasing characteristics _{of the E c} and P _r parameters as a function of electric field and frequency. The poled and non-poled samples behaved similarly (Fig. 2(a,b)). On the other hand at a constant frequency to increase the electric field is enhanced with an increase in the P _r E _c, changing the operating frequency of the electric field at constant P _r and E _c is decreased. The leakage current of Bi ₄ Ti ₃ O ₁₂ pellets was measured by applying a fixed electric field strength for 1,000 ms (Fig. 2(f,g)).

As the electric field strength increased from 10 to 120 kV/cm, the leakage current increased from 0.022 to 0.631 μA. The electric field dependent linear change of resistivity/resistivity of Bi ₄ Ti ₃ O _{12 pellets is shown in Fig. 10f.}

Fatigue analysis (Fig. 2h) of Bi ₄ Ti ₃ O ₁₂ ^{pellets showed constant polarization over 10 10} cycles or more, which is consistent with the well-known fatigue-free property of _{Bi 4} Ti ₃ O _{12 .}

Figure 2 (i,j) shows the frequency-dependent dielectric constant, loss and conductivity _{of the synthesized Bi 4} Ti ₃ O _{12 NPs.} The alignment of the charge dipoles at the grain boundaries between the grain boundaries and the material-electrode interface resulted in space charge or interface polarization along with bipolar polarization (ie molecular dipole).

The dielectric constant at 4 Hz is 89.87, which results in a space charge or space polarization along with a bipolar polarization (i.e. molecular dipole) by the alignment of the charge dipoles at the interface between the grain boundary and the material-electrode interface.

The dielectric constant of 89.87 at 4 Hz decreased to 79.24 at 3 MHz due to the decrease in space charge polarization and the involvement of dipole polarization.

The measured dielectric constant of the synthesized Bi ₄ Ti ₃ O ₁₂ NPs values is higher than reported elsewhere. The dielectric loss dropped from 0.08 to 0.01 each time the frequency was increased from 4 Hz to 4 kHz, then remained the same until 100 kHz and began to rise rapidly with frequency and reached 0.175 at 3 MHz. This is because the conductivity increases due to the _{Bi 4} Ti ₃ O ₁₂ switching dipole in the high-frequency delay depending on the applied electric field.

Figure 2j is the frequency-dependent conductivity of the Bi ₄ Ti ₃ O ₁₂ NPs shows a linear increase, sapdo is a SEM image of a pellet surface NPs Bi ₄ Ti ₃ O _12.

At low frequencies, the conductivity depends on the formation of long-range orders of mobile ion transport. At higher frequencies, the conductivity was increased by hopping of the free charge carriers trapped in the sample. In addition, both ionic and electron conduction mechanisms are applicable to represent the overall conduction process of _{Bi 4} Ti ₃ O _{12 .} Metal deficiency and oxygen vacancies in Bi ₄ Ti ₃ O ₁₂ are the source of ion conductivity. Electronic conductivity would be possible by polaron hopping between ^{Ti 4+} and Ti ^{3+ ions.}

Ferroelectric composite films were prepared in various weight ratios (ie, 0, 5, 10, 15, 20, 25 and 30% by weight) using a solution-casting technique (see Fig. 7). Crystalline phase analysis and structural, surface morphological, and ferroelectric analysis of various films are provided in the Supplementary Description Part to be described later (see FIG. 11 ). The energy harvesting ability of the films was systematically investigated by preparing BPCF-PNGs from them.

Figure 3a shows _{the optical image, flexible layer and device layer of fully packaged Bi 4} Ti ₃ O ₁₂ NPs/PVDF composite film-based piezoelectric nanogenerators (BPCF-PNGs). Figure 3b shows optical images of treated pure PVDF film (transparent), 30 wt% BPCF (opaque) and their ductility.

Specifically, Fig. 3. (a) _{Optical image showing the flexibility of the Bi 4} Ti ₃ O ₁₂ NPs/PVDF composite film-based piezoelectric nanogenerator (BPCF-PNG) and its device layer. (b) Optical images and flexibility of planar PVDF, BPCF. (c) (i,iii) Surface morphology and cross-sectional image of PVDF film, (ii,iv) Surface morphology and cross-sectional image of BPCF. (d) PE loops of polled BPCF (0, 20, 25 and 30 wt%). (e,f) Output voltage and current response of polled BPCF-PNGs when a constant force of 2N is applied. (g) Analysis of load resistance of BPCF-PNG (25% by weight). (h) Energy stored in commercial capacitors as a function of time and capacitance. (i) Cyclic stability of BPCF-PNG (25 wt %) over 2,000 s. (j) shows an exemplary diagram of performing power supply of commercial LCDs and LEDs according to the application of biomechanical force.

The surface morphology of the PVDF surface has a smooth and regular spherulite structure and a thickness of about 30 µm (Fig. 3c(i)), whereas the BPCF surface is rough and non-uniform and has a thickness of about 44-µm (Fig. 3c(ii)). )). Figure S6d shows the P-E loop of BPCF (un-poled) prepared at 5 Hz.

The PE loop of the poled BPCFs presented in Figure 3d (7 kV for 6 h at room temperature) shows ^{an improved spontaneous polarization of 1} μC/cm 2 for 25 wt % BPCF, due to the highly ordered electrical dipole. In this case, _{the uniform distribution of Bi 4} Ti ₃ O ₁₂ particles in the PVDF polymer had little effect on the polymer structure, improving polarization. Excess ceramic particles (eg, 30% by weight of Bi ₄ Ti ₃ O ₁₂ NPs) caused surface agglomeration and modified the PVDF structure to reduce polarization.

As a reference figure in conjunction with Figure 3, with reference to Figure 12, Figure 12 (a,b) shows the energy generated by non-polling (BPCF-PNGs) at a constant applied mechanical force of 2N provided by a linear motor. The original PVDF device generated a current (15 V, 35 nA), which increased for 25 wt% BPCF-PNG under the same applied force (up to 38 V, 130 nA), which was ferroelectric Bi ₄ Ti ₃ O ₁₂ It has already been shown by the PE loop of BPCF to be due to the synergistic effect of NPs and PVDF polymers.

Increasing the weight percentage of BPCF-PNG to about 30% by weight decreased the electrical output (21 V, 66 nA) upon application of force due to the agglomeration of _{Bi 4} Ti ₃ O _{12 NPs in the PVDF film.} The increased loading of BPCFs improved the dielectric constant over that of pure PVDF films, which in turn could affect the electromechanical coupling coefficient of BPCFs and reduce energy harvesting performance. The operating mechanism of the BPCF-PNG is similar to that of a traditional composite PNG device (shown schematically in Fig. 12c).

The reliability of the generated output was first evaluated by switching the polarity test at 1 N force of the original PVDF device. The results are presented in Fig. S13a. These results confirm that the output of the BPCF-PNG device is due to the stress-induced piezoelectric effect and not due to other interference.

Poled BPCF-PNGs performance was evaluated with the same force (Fig. 3(e,f)). The improved output (47V, 180nA) for the 25 wt% BPCF-PNG was due to the improved dipole orientation resulting in improved permanent polarization. BPCF PNG-output performance can also vary depending on other parameters, including particle shape, size BPCF, electric dipole orientation, P _r, the support polymer, filler amount, film thickness and the device active region.

Referring to reference figure 13 in conjunction with Figure 3, Figure 13 (b,c) shows the force-dependent (2, 4, 6N) electrical output of polled BPCF-PNG (25 wt %). As the applied force increased from 2N to 4N, the output increased from (47V, 180nA) to (56V, 220nA). Further increase in force did not affect the output. This indicated that 4N was the optimal applied force for BPCF-PNG. To calculate the instantaneous power density, load resistance analysis (100KΩ to 10GΩ) was performed (FIG. 3g).

BPCF-PNG produced a maximum power density of ^{12.7 mW/m 2} at a load matching resistance of 300 M, which is an optimal resistance. Comparing the performance of the proposed BPCF-PNG device with other devices (Table S1), it can be seen that it is suitable for real-time application. Load matching, charge/discharge and stability are essential characteristics of commercial devices. The charge/discharge behaviors of commercial electrolytic capacitors (0.1, 0.22, 1, 2.2 and 4.7 μF) were evaluated up to 100 s by BPCF-PNG output (Fig. 13(d,e)). The corresponding stored energy (E _c =½ CV ² ) is shown in FIG. 3H . A commercial 0.1 μF capacitor stored 0.98 mJ of energy for 80 s.

3I shows the device output endurance of over 2,000 seconds. No change in output voltage means that the device is well suited for real-time applications. In addition, the BPCF-PNG device was tested to utilize the biomechanical forces generated by finger-tapping (18V, 60nA), hand-tapping (30V, 120nA) and foot-tapping (38V, 160nA). The results are shown in Figs. 14(a-c). This result confirms that the proposed device can utilize energy in daily human exercise. Figure 3j shows the power supply of commercial LEDs/LCDs when hand-force is applied to the BPCF-PNG.

4 shows an exemplary diagram for implementing a real-time temperature environment monitoring system.

에서의 표면 형태. (g) 실험 SP-FHTT/비상 시스템의 광학 이미지. (h-k) 비상 경보 시스템의 두 가지 작동 조건 및 표시되는 메시지. (i) 40

미만(녹색 LED 켜짐) 및 (ii) 40℃ 초과(빨간색 LED 켜짐) 동작을 예시하고 있다.Specifically, Fig. 4. (a) Schematic diagram of a self-driven flexible ferroelectric high temperature thermistor (SP-FHTT) and the proposed emergency alarm system. (b) The temperature-dependent output of the SP-FHTT when a 4N force is applied. (c) Cumulative peak-to-peak voltage response of SP-FHTT as a function of temperature. (df) _{Cross-sectional images of Bi 4} Ti ₃ O ₁₂ films at room temperature and 260

surface morphology in (g) Optical image of the experimental SP-FHTT/emergency system. (hk) The two operating conditions of the emergency alarm system and the messages displayed. (i) 40

Below (green LED on) and (ii) above 40°C (red LED on) are illustrated.

In everyday life, it is important to accurately and sensitively monitor temperature in an environmentally friendly and cost-effective way. (Fig. 4a). SP-FHTT (Self-Powered flexible ferroelectric high-temperature thermistors (SP-FHTT) connected to the Arduino circuit) can be used as an early warning system in the industry or home to manage damage and save lives in the event of a disaster. have.

The detailed preparation procedure of SP-FHTT is given in the experimental section.

BPCF-PNG served as an independent electrical energy source to drive FHTT at temperatures ranging from room temperature to 260°C. The obtained voltage response is presented in Fig. 4b. At room temperature, the FHTT peak-to-peak voltage was higher than that of the BPCF-PNG output (under an applied force of 4 N at 1 GΩ), indicating that the FHTT has a high internal resistance (TΩ).

Here, two kinds of voltage peak patterns are observed for SP-FHTT. Region-I (room temperature ~ 120 °C) indicates that the change in the temperature-dependent resistance of the FHTT is small, so the change in the positive-negative voltage peak is minimal. On the other hand, since SP-FHTT showing a positive peak is very high compared to a negative peak as shown in FIG. 4B , the internal impedance of FHTT (variable load resistance) may be much higher than giga-ohm. For region-II (above 120°C), the difference in generation of positive and negative peaks in SP-FHTT is reduced and a uniform change is achieved between them (like a variable resistor) due to the significant variation in the temperature-dependent resistance of FHTT. The temperature-dependent cumulative peak-to-peak voltage of SP-FHTT had a nonlinear response (Fig. 4c) and a wide operating temperature range (window).

The active film thickness of FHTT was 20 μm, and Bi ₄ Ti ₃ O ₁₂ NPs particles (FIG. 15 shows EDS mapping) were uniformly distributed throughout the Kapton film (FIG. 4(d,e)). The SP-FHTT response was in good agreement with the temperature-dependent IV response of the FHTT at a DC bias voltage of ±100 V (Fig. 1(d,e) and Fig. 9). Multiple high-temperature measurements of high-temperature silicone oil slightly changed the surface morphology of the active layer (Fig. 4f).

SP-FHTT can be used as an environmental temperature early warning system/monitor by connecting an Arduino circuit and an LED/alarm indicator (Fig. 4g). The Arduino circuit is programmed with the following two operating conditions: the green LED turns on whenever the ambient temperature of the FHTT is lower than 40 °C (alarm OFF), and the red LED turns on whenever the ambient temperature is higher than 40 °C (alarm ON). (Fig. 4(h,i)). At the same time, a pop-up message indicating the hazard is displayed on the monitoring display (Fig. 4(j,k)).

These two operating conditions are valid whenever the BPCF-PNG output drives a self-powered FHTT sensor. The operating temperature of the FHTT affects the resistance value, and the voltage change directly controls the Arduino circuit. Then, the Arduino circuit sends a command signal to the monitoring/display device according to the voltage received from the CPNG device. This sensor demonstrates that the ferroelectric Bi ₄ Ti ₃ O ₁₂ NPs have dual functions as stand-alone power supply and high-temperature thermistors. To validate our results, a commercial NTC thermistor used instead of FHTT is driven by the CPNG device output (Figs. S11 and S12). The commercial NTC thermistor (ND03U00105J) output variation was in good agreement with the SP-FHTT result. In addition, the proposed FHTT has a wider operating temperature range (up to 260°C) than the conventional commercial NTC thermistor (145°C). Our device performance demonstrated that cost-effective ferroelectric thermistors based on _{Bi 4} Ti ₃ O _{12 NPs are ready for commercialization.}

_{5 shows an improved ferroelectric description of Bi 4} Ti ₃ O ₁₂ nanoparticles dual function (energy conversion, thermistor) for the low power consumption real-time emergency alert system described above in FIG. 4a.

4. Reference_Auxiliary explanation part

Hereinafter, it is a reference drawing (FIGS. 6 to 17) for auxiliary explanation (SI: supporting information) for explaining the concept applied to the above-described FIGS. 1 to 5 .

6 is a conceptual diagram of a synthesis process showing the sol-gel synthesis _{of Bi 4} Ti ₃ O _{12 NPs.} 7 is a manufacturing process conceptual diagram illustrating the preparation of PVDF and BPCFs. 8 shows an energy band diagram for bias voltage dependent conductivity of a symmetrical MSM structure.

9 provides a temperature-dependent IV measurement of FHTT at fixed bias. 10 shows PE loop measurements of _{Bi 4} Ti ₃ O ₁₂ pellets under different electric field/frequency conditions. 11 provides structural, functional and ferroelectric analysis of BPCF. Figure 12 provides the energy harvesting analysis and mechanism of action of BPCF-PNGs. Figure 13 provides an analysis of BPCF-PNG (25 wt %) and capacitor charge. 14 depicts harnessing biomechanical energy using BPCF-PNG (25 wt %). 15 is a morphological analysis of a _{Bi 4} Ti ₃ O _{12 film.} 16 shows a self-powered thermistor made from a commercial NTC thermistor. 17 shows a commercial NTC-based early warning/monitoring system. Table S1 compares the performance of the proposed BPCF-PNG with previously reported data.

8 is for explaining the electron transport process of a ferroelectric, and shows an energy band diagram for the bias voltage-dependent conductivity of a symmetric electrode MSM structure.

Specifically, FIG. 8 is a diagram of an energy band diagram for bias voltage dependent conductivity of a symmetric electrode MSM structure: (i) electrons tunneling from the left. (ii) Built-in conductivity due to ferroelectric effect. (iii) shows electrons tunneling from the right side (assuming the applied bias voltage is the right electrode and the left electrode connected to ground). (Vacuum: vacuum, Ferroelectric, P-type: ferroelectric, P-type)

In this case, it may be possible that the electrical polarity of the p-type Bi ₄ Ti ₃ O ₁₂ material reflects a small number of additional electrons in the conduction band. During a positive bias voltage, electrons move from the metal surface to Bi ₄ Ti ₃ O ₁₂ (right to left) and the current flows in the opposite direction. This is because the right metal electrode is connected to the positive voltage and the left metal is connected to the negative terminal or grounded. Similarly, during negative voltage, electrons _{will be transferred from the left metal surface to Bi 4} Ti ₃ O ₁₂ (left to right) as shown in Fig. S3. Both ion and electron conduction mechanisms are applicable to represent the overall conduction process of Bi ₄ Ti ₃ O _{12 .} Oxide ion conduction initiated by Bi deficiency and oxygen vacancies generated in the material processing process can be explained using the Krøger-Vink equations 1 and 2 below.

Hereinafter, definitions and formulas related to parameters of flexible ferroelectric high-temperature thermistors (FHTTs) described above in the embodiment of the present invention will be described.

FHTT parameter calculation

Thermistor constant (β):

The reliability of the thermistor material/component can be estimated using the thermistor constant (b), also known as the sensitivity index. Calculating the temperature dependent resistance of a material is an important parameter. The β value is evaluated using the following equation.

where T ₁ and T ₂ are two different temperatures in Kelvin (K), and RT ₁ and RT ₂ are the corresponding resistances (ohms (Ω)).

For example :

Considering two different temperatures 25°C and 260°C, the change in resistance is as follows (I-V analysis).

The value of β calculated with the help of equation (1) is:

β _(25-260) = 5119.50 K

Similarly, various thermistor constants were evaluated considering various temperature ranges and their values were tabulated as follows.

Stein-Hart Equation (S-H):

The SH equation is useful for making the relationship between the resistance (R) of a thermistor material and the range of its operating temperature (T). The SH coefficients a, b and c are constants for individual thermistors, unlike the temperature coefficient of resistance (a) and the thermistor constant (b), and should not be considered material constants. This equation is used as the resistance and three temperature points over the full range of the thermistor. Values of resistance are usually taken at the beginning, middle and end of the operating range. This gives the best results over the full operating range of the thermistor. The SH factor gives the best approximation between T and R over the full range of the thermistor with only three data points. The general form of the SH equation is

는 다른 계수보다 훨씬 작으며 일반적으로 계산에서 무시된다. 따라서 스타인하트-하트 계수는 다음 방정식을 사용하여 도출되었다.Terms

is much smaller than the other coefficients and is usually ignored in calculations. Therefore, the Steinhart-Hart coefficient was derived using the following equation.

where "T" is the angle in degrees Kelvin, and "A", "B" and "C" are coefficients derived as follows.

here,

The calculated values were directly applied to the equation below to find the S-H coefficient.

The proposed FHTT resistance was measured under three temperature conditions and the corresponding values were as follows:

Applying these values from the above equation, the derived S-H coefficient of FHTT is

A=5.381224e ^-3

B=-2.814078e ^-4

C= 2.608939e ^-7

The S-H coefficient is potentially useful for deriving resistance at a desired temperature and vice versa.

Temperature coefficient of resistance TCR(α)

The degree of temperature change, or change in the thermistor resistance fluctuation component per Kelvin, is called the temperature coefficient of resistance (α) and is usually expressed in %/°C or %/K. From the thermistor constant (β) of the material, the temperature coefficient of resistance (α) can be derived using the following equation.

where β = thermistor constant (K) and T = temperature (K).

In the above formula, the following values apply.

β = 5119.50 K and T = 25 +273.15 = 298.15 K

Calculated α per Kelvin change in temperature is:

C) = - 5.76 %/ K α(

C) = - 5.76 %/K

A negative TCR value indicates a thermistor resistance drop (NTC behavior) with increasing temperature. Here, α and β are both material constants, unlike the S-H coefficient, which varies with individual thermistors. The thermistor constant (b) can be derived using the S-H coefficient, and TCR can be obtained using the following equation.

Heat dissipation constant (δ)

The heat dissipation constant δ represents the amount of power required to heat the thermistor by 1°C when it is energized in air (mW/°C). When electric power (W) is applied to the thermistor at ambient temperature (Ta), and the temperature of the thermistor finally reaches temperature (T), the following equation is set from the conditions for deriving the dispersion constant (δ).

where P = power consumption (mW) of the thermistor, T = thermistor temperature (°C), and Ta = ambient temperature (°C). where P = I ² R.

Applying the following conditions to the above equation,

The obtained heat dissipation constant is:

δ = 3.95744 e ^-5 (mW/C)

activation energy (E _a )

The sensitivity to temperature sensing by FHTT is the E of electrical conduction._ais defined by the slope (β) of the logarithmic Arrhenius plot of electrical resistance on the Boltzmann constant and the reciprocal of the absolute temperature (l_nIt is calculated by multiplying by ρ) (1000/T as in FIG. 1H). E_areflects the energy required for hopping of charge carriers in the prepared sample. Typically 0.15 to 0.5 eV E_aMaterials with ? are suitable for NTC thermistor applications. The activation energy was obtained using the following equation.

In the above equation, k _B = Boltzmann constant (8.6173 10 ^-5 eV/K) and β _(25/260) = thermistor constant (5120 K). By applying the thermistor constant obtained in the above equation, the BiTO thermistor activation energy is:

E _a = 0.44116422 eV

Referring to FIG. 10, PE loop measurements of _{Bi 4} Ti ₃ O _{12 pellets under different conditions.} (a) Comparison of polled/unpolled samples at 50 KV/cm and 2 Hz. (b) Frequency-dependent PE loops of samples polled at 120 KV/cm and 1 to 200 Hz. (c) Electric field-dependent PE loops of samples polled from 5 Hz to 120 KV/cm and 2 Hz. (d) Electric field-dependent PE loops of polled samples at 4 Hz and 5 to 120 KV/cm. (e) Electric field-dependent PE loops of samples polled from 5 Hz to 120 KV/cm and 10 Hz. (f) Shows the calculated electric field-dependent resistance (R), the resistivity (ρ) of the polled sample.

Polyvinylidene Fluoride (PVDF):

Flexible PVDF has high electrical conductivity and can be easily fabricated by a variety of techniques. PVDF is a polyphasic polymer (α, β, γ, δ, ε) with different phase conformations as follows, and all trans to the β phase (TTTT), non-polar α and polar δ in chain form are (TGTG') form of trans and Gaussian, whereas the polar γ and non-polar ε conformations are (T3GT3G′), which have different properties depending on the structural conformation of each phase. Among them, the β phase has very high polarity, is ^{electroactive with a high dipole moment per unit cell (7 × 10 -30} C m), is suitable for piezoelectric applications, and is known to be γ semipolar with reasonable piezoelectric properties.

11 is a structure, function and ferroelectric analysis of BPCF. (a) XRD pattern (inset: Raman spectrum). (b) FT-IR spectra of PVDF powder, sonicated PVDF and BPCF films. (c) P-E loop measurements of pure PVDF and BPCF films (non-polling).

The most available and stable form of PVDF is the non-polar α phase. There are many reports for converting PVDF from non-electroactive phase to electro-active phase, such as electrospinning and introduced ions, conductive fillers and additives such as graphene, CNT, and ZnO [6,7]. One of the simplest and most effective conversion methods is the ultrasonic method. Compared with the regular stirring process, sonication leads to better polarization in the membrane, which has been reported to align more dipole leads, which is the reason behind the improved piezoelectric performance [8]. Here, an ultrasonically driven PVDF membrane was used to fabricate composite films from _{Bi 4} Ti ₃ O _{12 NPs for high-performance flexible PNGs.}

XRD, Raman and FT-IR analysis of BPCF :

To confirm the effect of PVDF on Bi ₄ Ti ₃ O ₁₂ NPs, the loading amount was analyzed by XRD and Raman spectrum measurement. S6a and its inset show the XRD and Raman spectra of the composite film measured under the same conditions as _{pure Bi 4} Ti ₃ O _{12 NPs.} The observed XRD spectrum shows that there is no phase change of _{Bi 4} Ti ₃ O ₁₂ NPs, except that the intensity reduction of the XRD peak and a similar kind of response are observed in the Raman spectrum, and Bi with reduced intensity and slight shift. The same vibration of ₄ Ti ₃ O _{12 NPs is explained.} This result confirms that PVDF does not affect the structural properties of _{Bi 4} Ti ₃ O _{12 NPs.}

Since ferroelectric PVDF polymers have multiple phases, it is necessary to characterize the functional properties of the prepared pure films and composite films to identify the phases of PVDF. The FTIR spectra of commercial PVDF powder, ultrasonically driven PVDF and composite film are shown in Fig. S6b. FTIR spectra of PVDF precursor powder show peaks at 763, 797, 870 and 974 cm ⁻¹ , suggesting that PVDF has a dominant α phase. The sonicated PVDF film spectrum confirmed that the α-phase peak decreased and ^{a new peak occurring at 840 cm -1} belonged to the representative peak of the β-phase. Recently, it was evaluated as a common peak of the β and γ phases, and the shoulder peaks of the strong β and γ phases were mainly exhibited. The total energies of the β and α phases produced are correspondingly -23.95 and -25.21 kJ/mol, indicating that the electroactive β phase is less stable than the α phase. During sonication, the energy gap between the two phases is reduced, leading to a highly polar β (TTTT) phase transition. Even the addition of Bi ₄ Ti ₃ O ₁₂ NPs which loads the electroactive polymer on the PVDF matrix Bi ₄ Ti ₃ O ₁₂ NP stress of - due to the inductive effect of different PVDF not changed by a slight change. From the observed results, it was confirmed that the ultrasonic method induced electroactive β and γ phases in PVDF and that the electroactive phase was maintained in the composite membrane as well. Electroactive PVDF with ferroelectric Bi ₄ Ti ₃ O ₁₂ NPs is expected to contribute to electrical performance improvement.

Analysis of ferroelectric PE loops in BPCF (non-poled):

All prepared pure BPCF hysteresis loops were measured at a constant frequency of 5 Hz at room temperature and are provided in Fig. 11c. The results showed that BPCF loaded with 25 wt% showed the highest spontaneous and residual polarization, which was attributed to the combined effect of _{Bi 4} Ti ₃ O _{12 NPs and PVDF polarization.} In this case, the Bi ₄ Ti ₃ O ₁₂ particles are uniformly distributed on the PVDF polymer without changing much of the polymer structure, resulting in improved polarization, and the increase in the ceramic particles causes surface agglomeration (Bi ₄ Ti ₃ O _{12 ).} 30 wt% of NPs) and modify the PVDF structure to reduce polarization. Changes in polarization will affect the device energy harvesting performance.

Working mechanism of BPCF-PNG device

Figure 12 shows the energy harvesting analysis and operating mechanism of BPCF-PNGs. 12(a,b) Output voltage and current response of non-polling BPCF-PNGs to 2N mechanical force. It is the mechanism of operation of the BPCF-PNGs device in three conditions: (c) (i) force, (ii) applied force, and (iii) force release condition. (Voltage: Voltage, Current: Current, Time: Time, Kapton -Packing: Kapton-Packing,Copper electrode: Copper electrode, Piezocomposite film: Piezoelectric composite film, PDMS-Packing: PDMS-Packing, Dipoles: Dipole)

The mechanism of BPCF-PNG device energy generation is schematically presented in Fig. 12c.

As shown in Fig. 12c(i), in the initial case with no force applied, the device contains an existing electric dipole in any direction and the net charge transfer is zero.

Therefore, no electrical response was observed in the CPNG device. As shown in Fig. 12c(ii), when a deformation occurs in the device due to the applied force, the dipoles tend to align in one direction due to the deformation-inducing effect, and the charge is transferred from one electrode to the other in a half cycle. It becomes possible to observe the electrical response from the CPNG device.

When the applied force is removed, the dipoles will align in opposite directions as shown in Figure 12c(iii), and charge transfer will occur in reverse, completing the other half cycle of the electrical response output. The proposed mechanism is continuous and generates a continuous electrical response under a linear mechanical force.

13 shows the force analysis results for BPCF-PNG and capacitor charging.

Fig. 13(a) Switching polarity test of BPCF-PNG (pure PVDF) at 1N force. (b,c) Electrical response (25 wt%) of BPCF-PNG to various forces. (d,e) Commercial capacitor charging and discharging analysis using BPCF-PNG (25 wt%) output.

14 is a biomechanical energy utilization using BPCF-PNG (25% by weight), (a) an image of the condition of applying a biomechanical force such as finger, hand, and foot tapping. (b,c) Shows the electrical response results measured under the applied biomechanical force. (Finger tapping: Finger tapping, Hand tapping: Hand tapping, Leg tapping: Foot tapping, Voltage: Voltage, Time: Time)

_{15 is a morphological analysis result of the Bi 4} Ti ₃ O ₁₂ film described above in Example of the present invention, (ad) Bi ₄ Ti ₃ O ₁₂ Cross-sectional FE-SEM, EDS mapping of the film Bi, Ti and O elements show the distribution.

Below, the self-powered thermistor demonstration (model: ND03U00105J) using a commercial NTC thermistor is shown.

16 is a diagram showing the time connection of a self-powered thermistor using a commercial NTC thermistor, and FIG. 16 (a) is a schematic diagram of a self-powered thermistor and its application to development of an early warning system. (b) Temperature dependent resistance of commercial NTC (0°C to 145°C) measured using a multimeter. (c,d) The temperature-dependent electrical response results of the self-powered thermistor [BCFCF-PNG (25 wt%) output driving the NTCF thermistor] measured using an electrometer is shown.

16 shows a schematic overview of various units presented in a commercial NTC-based temperature sensing and monitoring unit. Initially, the NTC resistance to various temperatures was measured and plotted as shown in Fig. S11b, and the NTC had a resistance of 3.35 MΩ at 0 °C, which later nonlinearly dropped to 0.09 MΩ at 145 °C, the characteristic behavior of NTC. lost.

The inset shows a commercial NTC of silicone oil. CPNG output was measured by replacing only commercial NTC instead of FHTT under the same conditions as in FIG. 4b. The measured electrical output is shown in Fig. 16c showing the non-linear drop of the voltage output equal to the resistance.

The resulting peak pattern was smooth and very minute changes with each temperature were observed due to the very low resistance of commercial NTCs. The voltage output for the obtained temperature was plotted and shown in Fig. S11d. From this, the proposed FHTT has the advantage of high resistance variation for each temperature and wide temperature operating range compared to commercial NTCs, which may be advantageous for use in many applications than conventional commercial NTCs.

17 shows an example demonstrating a commercial NTC-based early warning/monitoring system. 17 (a) A warning system setting image. (b) Monitoring and display unit response below 40°C. (c) Monitoring and display unit response above 50°C. (d) It shows the status of the display unit under various temperature conditions. (Interfacing & Communication Unit: Interfacing/Communication Unit, Monitoring Unit: Monitoring Unit, Green LED On & Buzzer off: Green LED On & Buzzer Off)

{Table 4: Comparison of BPCF-PNG Electrical Responses}

Although the preferred embodiment of the present invention has been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also provided. is within the scope of the

Flexible Bi ₄ Ti ₃ O ₁₂ NPs film/Kapton : Flexible Bi ₄ Ti ₃ O ₁₂ NPs film/Kapton
Perovskite ferroelectric nanoparticles : Perovskite ferroelectric nanoparticles
Flexible ferroelectric high temperature thermistor
Region : Region
Voltage : voltage
Time (s) : Time (seconds)
Alert signals: Alert signals
Safety signal : Safety signal
Danger signal : Danger signal
Warning system: warning system
Flexible: ductility
Nanogenerator : Nanogenerator
Power density : power density
Load Resistance: load resistance

Claims (8)

delete delete delete delete delete delete a) synthesizing a mixture by mixing a precursor material and a solvent to form bismuth titanate (Bi ₄ Ti ₃ O _{12 );}
b) calcining the mixture to form bismuth titanate nanoparticles (Bi ₄ Ti ₃ O ₁₂ NPs);
c) drying a mixture obtained by adding the bismuth titanate nanoparticles (Bi ₄ Ti ₃ O _{12 NPs) to a PVDF solution to form a composite film (Bi 4} Ti ₃ O ₁₂ NPs/PVDF composite films: BPCF);
d) cutting the composite film to form a unit composite film, and laminating a copper (Cu) film on both surfaces of the unit composite film; includes
After step d),
e) forming an insulating PDMS polymer layer on an upper copper film of the copper film, and forming a Kapton film layer on a lower portion of the lower copper film; A bismuth titanate-applied composite film-based piezoelectric nanogenerator manufactured by a method of manufacturing a bismuth titanate-applied composite film-based piezoelectric nanogenerator further comprising a.
a sensing unit for sensing temperature-related information;
a control unit including an interface for collecting and processing information transmitted from the sensing unit and transmitting a control signal to an external terminal;
a monitoring unit that transmits a light-emitting or audio signal set according to a control signal of the control unit; and
and a display unit for displaying the operation status of the sensing unit, the control unit, and the monitoring unit.
The sensing unit is
a bismuth titanate-based flexible ferroelectric thermistor device (FHTT) comprising a structure in which highly crystalline ferroelectric Bi4Ti3O12 nanoparticles are brush-coated on a flexible Kapton film; and
_{A composite film (Bi 4} Ti ₃ O ₁₂ NPs/PVDF composite films: BPCF) prepared by drying a mixture obtained by adding the bismuth titanate nanoparticles (Bi4Ti3O12 NPs) to a PVDF solution is cut to form a unit composite film, a composite film-based piezoelectric nanogenerator (BPCF-PNG) having a structure in which a copper (Cu) film is laminated on both sides of the unit composite film and having a structure connected in parallel with the bismuth titanate-based flexible ferroelectric thermistor device;
A real-time environmental temperature monitoring system of a self-generation structure comprising a.

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