Wide-temperature-range component gradient laminated pyroelectric ceramic and preparation method thereof

Abstract

The invention relates to a wide-temperature-range component gradient laminated pyroelectric ceramic and a preparation method thereof. The wide-temperature-range component gradient laminated pyroelectric ceramic is formed by compounding a plurality of component layers, the chemical composition general formula of each component layer is (1-x) (Pb < 0.985 > La < 0.01 >) (Zr < 0.93 > Ti < 0.07 >) O < 3-x > BiScO3, x is the mole fraction of the component BiScO3 and is larger than or equal to 0 and smaller than or equal to 0.012, and x is larger than or equal to 0 and smaller than or equal to 0.012. X among the component layers is in gradient change. The preparation method of the wide-temperature-range component gradient laminated pyroelectric ceramic comprises the following steps: preparing raw film sheets forming a plurality of component layers by adopting a tape casting method according to the chemical compositions of the component layers, then laminating the raw film sheets of the component layers according to a gradient change mode of x values, pressing into a blank body, and carrying out heat treatment on the blank body to obtain the wide-temperature-range component gradient laminated pyroelectric ceramic. The blank is subjected to glue discharging and sintering, and the wide-temperature-zone component gradient laminated pyroelectric ceramic is prepared.

Description

Technical Field

[0001] The present invention belongs to the field of pyroelectric ceramics, and particularly relates to a composition gradient laminated pyroelectric ceramic with a wide temperature range and a preparation method thereof. Background Art

[0002] The pyroelectric effect can be directly used in aspects such as infrared detection, thermal-electric energy conversion, and thermal Joule applications. Pyroelectric thick-film ceramics have good performance and can be compatible with current integrated circuit processes, and have great application prospects and market value in fire prevention, anti-theft, lamp switches, and information products.

[0003] Currently, the problems encountered in the application of pyroelectric materials in the detection field mainly focus on: the pyroelectric performance and the working temperature range of pyroelectric ceramics restrict each other. 1) Since the spontaneous polarization of pyroelectric ceramics only exists below the Curie temperature, pyroelectric ceramics for pyroelectric detection have a Curie temperature higher than room temperature to ensure normal use of the ceramics at room temperature, such as Pb(Zr,Ti)O 3 , (Pb,La)(Zr,Ti)O 3 , LiTaO 3 , (Bi,Na)TiO 3 , etc. Although this type of intrinsic pyroelectric ceramics has a relatively wide working temperature range, the pyroelectric coefficient (<10×10 -8 C / cm 2 ·K) and the figure of merit of detectivity (~2μPa -1 / 2 ) at room temperature are often low, which greatly reduces the detection sensitivity. 2) For ceramics with a Curie temperature close to room temperature, such as Ba(Sr,Ti)O 3 , although the pyroelectric coefficient at room temperature is high, the working temperature range is too narrow. And this type of field-induced pyroelectric ceramics must work under a DC bias field, and the complex circuit design and device manufacturing also hinder the development of miniaturization of pyroelectric detectors. It can be seen that neither of these two types of pyroelectric ceramics can achieve both high pyroelectric performance and a wide working temperature window.

[0004] (Pb,La)(Zr,Ti)O 3 -based (PLZT) ceramics have high polarization intensity and rich phase structures. Recent research has found that there is also a transitional phase transformation (R3c-R3m) in PLZT (J.Am.Ceram.Soc.2023; 106:4678-4698). With ZrO 2With the increase of the content, the phase transition temperature decreases from 116 °C to 40 °C. Among them, this phase transition leads to a sudden increase in pyroelectric performance. On the one hand, compared with the intrinsic pyroelectric material, the pyroelectric performance caused by this phase transition is improved by 1-2 orders of magnitude; on the other hand, compared with the field-induced pyroelectric material (J. Mater. Chem. C. 2020; 8: 782), this type of phase transition has the advantages of small strain before and after phase transition, no need for external electric field, and adjustable phase transition temperature. However, for pyroelectric detector applications, it is mainly applied near room temperature to human body temperature. How to use the transitional phase transition (R3c-R3m) to simultaneously achieve high pyroelectric performance and wide working temperature window in this temperature range is an urgent problem to be solved.

[0005] Therefore, we need to further regulate (Pb, La)(Zr, Ti)O 3 Based ceramics phase transition, greatly optimize its pyroelectricity and working temperature range near room temperature to human body temperature, realize the improvement of pyroelectric performance in a wide temperature range near room temperature to human body temperature, and make it play an important value in the fields of uncooled infrared detection technology or thermoelectric energy conversion. Summary of the Invention

[0006] In order to solve the above problems, the present invention aims to provide a wide-temperature-range composition gradient laminated pyroelectric ceramic and its preparation method, which is convenient for large-area preparation and easy to integrate, and has high pyroelectric coefficient and detection figure of merit in the working range of 30-50 °C.

[0007] The present invention further regulates the phase transition of (Pb, La)(Zr, Ti)O 3 By introducing BiScO 3 Based ceramics phase transition, greatly optimize the pyroelectricity and working temperature range of PLZT-based ceramics near room temperature to human body temperature. Due to the wide adjustable range of the transitional phase transition temperature of PLZT-based ceramics, the present invention uses the tape casting process and compositional gradient thick film lamination to achieve the improvement of pyroelectric performance in a wide temperature range near room temperature to human body temperature, which has important value for the practical applications in the fields of uncooled infrared detection technology or thermoelectric energy conversion.

[0008] The wide-temperature-range composition gradient laminated pyroelectric ceramic of the present invention is a composition gradient lead lanthanum zirconate titanate-based ceramic. First, on the basis of (Pb 0.985 La 0.01 )(Zr 0.93 Ti 0.07 )O 3 Introduce BiScO 3 To promote (Pb 0.985 La 0.01 )(Zr 0.93 Ti 0.07 )O 3The transition from the ferroelectric phase to the antiferroelectric phase indirectly affects the movement of the transitional phase change (R3c-R3m) towards room temperature during this process, thereby obtaining (Pb 0.985 La 0.01 )(Zr 0.93 Ti 0.07 )O 3 -xBiScO 3 ceramic materials with different phase transition temperatures in the range of room temperature to human body temperature. Subsequently, the ceramic components with different phase transition temperatures are laminated by the doctor blade method to prepare a lead lanthanum zirconate titanate-based ceramic with a composition gradient. The lead lanthanum zirconate titanate-based ceramic with a composition gradient forms a gradient transitional phase change (R3c-R3m) in the temperature range of room temperature to 50 °C, thereby improving the pyroelectric performance of the lead lanthanum zirconate titanate-based pyroelectric ceramic in a wide temperature range.

[0009] On the one hand, the present invention provides a pyroelectric ceramic with a wide temperature range and a composition gradient laminate, which is composed of multiple component layers laminated together. The general chemical formula of each component layer is: (1-x)(Pb 0.985 La 0.01 )(Zr 0.93 Ti 0.07 )O 3 -xBiScO 3 , where x is the molar fraction of the component BiScO 3 , and 0 ≤ x ≤ 0.012; x changes in a gradient among multiple component layers.

[0010] Preferably, the gradient of the x value between adjacent two component layers among the multiple component layers is 0 to 0.012. Preferably, the x value gradient of the multiple component layers increases.

[0011] Preferably, each component layer is composed of 2 to 8 thin sheets laminated together; the thickness of each thin sheet is 0.010 to 0.015 mm.

[0012] Preferably, the relative dielectric constant of the pyroelectric ceramic with a wide temperature range and a composition gradient laminate is 300 to 360 at 25 °C and a test frequency of 1 kHz.

[0013] Preferably, the pyroelectric coefficient p of the pyroelectric ceramic with a wide temperature range and a composition gradient laminate is 40 to 54×10 -8 C·cm -2 ·K -1 , the figure of merit factor F i of the current response is 1.5 to 2.2×10 -7 m / V, the figure of merit factor F v of the voltage response is 50 to 80 m 2 / C, and the figure of merit factor F d of the detectivity is 2 to 5×10-2 Pa -1 / 2 。

[0014] On the other hand, the present invention also provides a method for preparing the wide-temperature-range composition-gradient laminated pyroelectric ceramic as described above, comprising: (1) According to the molar percentages of the chemical composition general formula, using analytically pure Pb 3 O 4 , La 2 O 3 , ZrO 2 , TiO 2 , Bi 2 O 3 and Sc 2 O 5 as raw materials, using anhydrous ethanol as the medium, and performing the first ball milling to obtain a wet powder slurry; (2) Drying and pre-sintering the obtained wet powder slurry to obtain a first powder; (3) Performing the second ball milling on the obtained first powder using anhydrous ethanol as the medium, and drying the wet powder obtained after the second ball milling to obtain a second powder; (4) Adding the obtained second powder to a solvent and a dispersant and performing high-energy ball milling to obtain a uniformly dispersed slurry, and adding a binder and a plasticizer to the slurry and performing high-energy ball milling to obtain a uniformly mixed casting slurry; (5) Casting the obtained casting slurry onto a PET film using a casting machine to obtain a green film, and leaving it to dry at room temperature for 4 - 6 h; (6) Cutting the prepared green films with different x values respectively to obtain green film pieces, stacking the green film pieces with each x value to form a group layer, then stacking the group layers together in the order of the gradient change of the x value, pressing the stacked layers into a compact green body using a hot press, degreasing the green body to obtain a degreased green body, and sintering the degreased green body.

[0015] Preferably, the parameters of the first ball milling in step (1) and / or the second ball milling in step (3) include: the grinding balls are zirconia balls; the mass ratio of the ball milling raw materials, grinding balls and ball milling solvent is 1:(9 - 10):(4 - 5); the diameter ratio of the grinding balls is 0.8 - 1 mm, and the mass ratio is 1:(1 - 2):(1 - 2); the drying temperature is 80 - 100 °C, and the time is 4 - 6 h.

[0016] Preferably, in step (2), the pre-sintering temperature is 800 - 850 °C, the time is 2 - 3 h, and the heating rate is 1.5 - 2 °C / min.

[0017] Preferably, in step (4), the parameters of the high-energy ball milling are: the ball milling tank is a nylon tank, and the ball milling is ZrO 2The ball; the solvent is anhydrous ethanol and ethyl acetate, and the mass ratio is (1 to 1.5):(2 to 3); the dispersant is a polyethylene oxide functional polymer (AKM-0531) or tributyl phosphate, preferably AKM-0531; the binder is at least one of polyvinyl alcohol dibutyl ester, polyethylene glycol, and polyvinyl alcohol; the plasticizer is at least one of dioctyl phthalate, polyethylene glycol, and dibutyl phthalate.

[0018] Preferably, in step (5), the casting rate is 8 to 10 mm / s; the thickness of the obtained green film is 0.010 to 0.015 mm.

[0019] Preferably, in step (6), the debinding parameters include: the debinding temperature is 650 to 700 °C, the holding time is 6 to 8 h, and the heating rate is 0.5 to 1 °C / min.

[0020] Preferably, in step (6), the sintering parameters include: first heating to 1000 to 1050 °C at a heating rate of 3 to 4 °C / min, and then heating to 1100 to 1200 °C at a heating rate of 2 to 3 °C / min, and holding for 2 to 2.5 h.

[0021] Preferably, after the body is sintered, it further includes: applying silver electrodes to two surfaces of the sintered ceramic, and placing it in a muffle furnace to heat to 650 to 700 °C at a heating rate of 2 to 3 °C / min and holding for 30 to 60 min, and then polarizing in silicone oil at 100 to 120 °C; wherein, the polarization electric field is 20 to 30 kV / cm, and the polarization time is 20 to 30 min.

[0022] The present invention indirectly adjusts the ferroelectric-antiferroelectric phase transition of lead lanthanum zirconate titanate-based ceramics to room temperature by introducing BiScO 3 to further regulate the ferroelectric-antiferroelectric phase transition of lead lanthanum zirconate titanate-based ceramics. This type of phase transition involves a change in the space group of the ferroelectric trigonal phase structure induced during the temperature increase process, changing from R3c to R3m. BiScO 3 In the component, the 6p orbital of Bi 3+ hybridizes with the 2p orbital of O 2- in the PLZT-based ceramic to cause the oxygen octahedron in the perovskite structure to undergo a torsional distortion. At the same time, Sc 3+ is slightly larger than Zr 4+ / Ti 4+ in ionic radius to make the unit cell in the PLZT ceramic larger, generating lattice strain to promote the destruction of ferroelectric long-range order and the transformation to disorder. As BiScO 3The content is increased to 0.012 mol, which can stabilize the antiferroelectric phase near room temperature, indirectly adjust the transition-type phase change temperature near room temperature, and optimize its pyroelectricity and working temperature range within the range of room temperature to human body temperature. Compared with the non-phase-change type pyroelectric ceramics in the prior art, the composition gradient laminated pyroelectric ceramics prepared by the present invention have a higher pyroelectric coefficient near room temperature to human body temperature (about 5 to 8 times that of traditional non-phase-change type pyroelectric ceramics), and maintain high pyroelectric performance within a wide temperature range (room temperature to 50 °C), which are of great value for the practical applications of this ceramic in the fields of uncooled infrared detection technology or thermoelectric energy conversion, etc.

[0023] Beneficial effects:

[0024] (1) The composition gradient laminated pyroelectric ceramics prepared by the present invention have excellent performance and a wide working range, and are expected to be applied in the field of uncooled infrared detection. The relative dielectric constant of the laminated pyroelectric ceramics after polarization is 300 - 360 and the dielectric loss is less than 0.02 at 25 °C and a test frequency of 1 kHz. The pyroelectric coefficient of the polarized laminated ceramics is 40 - 54×10 -8 C·cm -2 ·K -1 , the figure of merit factor F i of the pyroelectric current response is 1.5 - 2.2×10 -7 m / V, the figure of merit factor F v of the pyroelectric voltage response is 50 - 80 m 2 / C, and the figure of merit factor F d of the detectivity is 2 - 5×10 -2 Pa -1 / 2 .

[0025] (2) The composition gradient lead lanthanum zirconate titanate-based pyroelectric ceramics of the present invention are prepared by the tape casting method, can be made of industrial raw materials, and the preparation process is stable. Large-scale production can be achieved using equipment, which is convenient for industrial production. Description of the drawings

[0026] Figure 1 is a schematic diagram of the gradient lamination of the present invention; Figure 2 is a process flow chart of the preparation of the composition gradient lead lanthanum zirconate titanate-based ceramics of the present invention; Figure 3 is a graph showing the change of the polarization intensity of the composition gradient laminated pyroelectric ceramics of Example 5 of the present invention with temperature; Figure 4 is a graph showing the change of the polarization intensity of the composition gradient laminated pyroelectric ceramics of Example 6 of the present invention with temperature; Figure 5 is a graph showing the change of the polarization intensity of the composition gradient laminated pyroelectric ceramics of Example 7 of the present invention with temperature; Figure 6 It is the polarization intensity vs. temperature curve of the composition gradient laminated pyroelectric ceramics in Example 8 of the present invention; Figure 7 It is the relative dielectric constant vs. temperature curve of the composition gradient laminated pyroelectric ceramics in Examples 5, 6, 7, and 8 of the present invention within the range of room temperature to 300 °C; Figure 8 It is the pyroelectric coefficient vs. temperature curve of the composition gradient laminated pyroelectric ceramics in Examples 5, 6, 7, and 8 of the present invention; Figure 9 It is the figure of merit vs. temperature curve of the composition gradient laminated pyroelectric ceramics in Examples 5, 6, 7, and 8 of the present invention; Figure 10 (a) is the dielectric constant vs. temperature curve of the pyroelectric ceramic with the chemical composition of 0.984(Pb 0.985 La 0.01 )(Zr 0.93 Ti 0.07 )O 3 -0.016BiScO 3 (x = 0.016) in Comparative Example 1; (b) is the polarization intensity vs. temperature curve of the pyroelectric ceramic with the chemical composition of 0.984(Pb 0.985 La 0.01 )(Zr 0.93 Ti 0.07 )O 3 -0.016BiScO 3 (x = 0.016); (c) is the pyroelectric coefficient vs. temperature curve of the pyroelectric ceramic with the chemical composition of 0.984(Pb 0.985 La 0.01 )(Zr 0.93 Ti 0.07 )O 3 -0.016BiScO 3 (x = 0.016); (d) is the pyroelectric coefficient vs. temperature curve of the pyroelectric ceramics prepared from the green films of Examples 1 - 4 and Comparative Example 1. Detailed implementation manners

[0027] To further illustrate the content, features and actual effects of the present invention, the present invention will be described in detail below with reference to examples. It should be noted that the modified methods designed in the present invention are not limited to these specific implementation manners. Without departing from the spirit and connotation of the design of the present invention, equivalent replacements and modifications made by those skilled in the art on the basis of reading the content of the present invention are also within the scope of protection required by the present invention.

[0028] The present invention provides a composition-gradient lead lanthanum zirconate titanate-based pyroelectric ceramic, which is composed of multiple laminated layers. The general chemical formula of each laminated layer is: (1-x)(Pb 0.985 La 0.01 )(Zr 0.93 Ti 0.07 )O 3 -xBiScO 3 , where x is the mole fraction of the component BiScO 3 , and 0≤x≤0.012; x shows a gradient change among multiple laminated layers. If x>0.012, it shows a stable antiferroelectric phase at room temperature, and a stable room-temperature ferroelectric phase cannot be formed after high-temperature polarization, which results in no pyroelectric effect. Thus, it can be seen that for the laminated components, adding components without pyroelectric effect is of no benefit to regulating the pyroelectric performance of the gradient temperature change.

[0029] It should be noted that the composition-gradient lead lanthanum zirconate titanate-based pyroelectric ceramic provided by the present invention is based on (Pb 0.985 La 0.01 )(Zr 0.93 Ti 0.07 )O 3 , doped with the component BiScO 3 . By laminating tape-cast sheets with different doping amounts of BiScO 3 , the transition-phase transformation temperature appears in a temperature range, thereby forming a gradient transition-type phase transformation and further expanding the working temperature range of the pyroelectric ceramic.

[0030] The function of introducing the component BiScO 3 in the PLZT-based ceramic of the present invention is as follows: The 6p orbit of Bi 3 in BiScO 3+ hybridizes with the 2p orbit of O 2- in the PLZT ceramic, causing the oxygen octahedron in the perovskite structure to undergo torsional distortion. At the same time, the ionic radius of Sc 3+ is slightly larger than that of Zr 4+ / Ti 4+ . The ionic radius is slightly larger (r Sc3+ = 0.87A, r Zr4+ = 0.72, r Ti4+ = 0.605), making the unit cell of the PLZT ceramic larger, generating lattice strain and promoting the destruction of the ferroelectric long-range order and the transformation to disorder. As the content of BiScO 3 increases from 0 to 0.012 mol, the antiferroelectric phase is stabilized near room temperature, indirectly promoting the adjustment of the transition-type phase transformation to near room temperature. Subsequently, four thick films with different BiScO 3 contents are prepared by the tape-casting method, and according to BiScO3 Four thick films are stacked into a gradient ceramic in the order of increasing content. In this order, as the temperature gradually increases, components with different transitional phase change temperatures respond and undergo phase changes in sequence, thereby achieving an improvement in pyroelectric performance in a wide temperature range. Meanwhile, the influence of different stacking orders on pyroelectric performance was also studied.

[0031] In an embodiment of the present invention, the gradient of the x value between two adjacent group layers among the multiple group layers is 0 to 0.012. For example, the multiple group layers can be divided into 4 layers, where x is 0, 0.004, 0.008, 0.012 in sequence, and the corresponding chemical formula compositions are: (Pb 0.985 La 0.01 )(Zr 0.93 Ti 0.07 )O 3 , 0.996(Pb 0.985 La 0.01 )(Zr 0.93 Ti 0.07 )O 3 -0.004BiScO 3- , 0.992(Pb 0.985 La 0.01 )(Zr 0.93 Ti 0.07 )O 3 -0.008BiScO 3 . When four group layer flakes with different BiScO 3 doping amounts are laminated, the pyroelectric coefficient of this composition gradient lead lanthanum zirconate titanate-based pyroelectric ceramic is 49 - 54×10 -8 C·cm -2 ·K -1 , and can remain stable within 30 - 50°C.

[0032] The following exemplarily illustrates a preparation method of a wide temperature range composition gradient laminated pyroelectric ceramic provided by the present invention (as Figure 2 shown).

[0033] Step S1, according to the molar percentage of the chemical composition general formula, using analytical pure Pb 3 O 4 , La 2 O 3 , ZrO 2 , TiO 2 , Bi 2 O 3 and Sc 2 O 5 , using absolute ethanol as the medium, perform the first ball milling to obtain a wet powder slurry.

[0034] In an alternative embodiment, the parameters of the ball milling include: the ball milling jar is a nylon jar, and the grinding balls are ZrO 2 balls. The rotation speed of the ball milling is 300 - 360 r / min, and the ball milling time is 4 - 5 h; the mass ratio of the raw material, grinding balls and solvent is 1:(4.5 - 5):(1.5 - 2); the diameter ratio of the grinding balls is (2 - 2.5):(6 - 6.5):(8 - 8.5), and the mass ratio is 1:(1 - 2):(1 - 2).

[0035] Step S2, drying the obtained wet powder slurry to obtain a dry powder.

[0036] In an alternative embodiment, the drying temperature is 80 - 100 °C, and the time is 4 - 6 h.

[0037] Step S3, pre-sintering the obtained dry powder to obtain a first powder.

[0038] In an alternative embodiment, the pre-sintering is by the traditional solid-phase method. The pre-sintering temperature is 800 - 850 °C, the time is 2 - 3 h, and the heating rate is 1.5 - 2 °C / min.

[0039] Step S4, performing a second ball milling on the obtained first powder with absolute ethanol as the medium to obtain a uniformly mixed wet powder slurry.

[0040] In an alternative embodiment, the parameters of the second ball milling are: the grinding balls are zirconia balls; the mass ratio of the ball milling raw material, grinding balls and ball milling solvent is 1:(9 - 10):(4 - 5); the diameter ratio of the grinding balls is 0.8 - 1 mm, and the mass ratio is 1:1 - 2:1 - 2. The rotation speed of the ball milling is 300 - 360 r / min, and the ball milling time is 4 - 6 h.

[0041] Step S5, drying the obtained wet powder slurry to obtain a second powder.

[0042] In an alternative embodiment, the drying temperature is 80 - 100 °C, and the time is 4 - 6 h.

[0043] Step S6, adding the obtained second powder, solvent and dispersant, and performing high-energy ball milling to obtain a uniformly dispersed slurry.

[0044] In an alternative embodiment, the parameters of the high-energy ball milling include: the ball milling jar is a nylon jar, and the grinding balls are ZrO 2Ball; the mass ratio of the ball-milling raw material, grinding balls and ball-milling solvent is 1:(9 - 10):(4 - 5); the diameter ratio of the grinding balls is 0.8 - 1 mm, and the mass ratio is 1:(1 - 2):(1 - 2). The solvent is anhydrous ethanol and ethyl acetate, and the mass ratio is (1 - 1.5):(2 - 3); the dispersant is poly(ethylene oxide) functional polymer (AKM-0531) or tributyl phosphate, preferably AKM-0531. The plasticizer is at least one of dioctyl phthalate, polyethylene glycol, dibutyl phthalate; the rotation speed of the high-energy ball milling is 300 - 360 r / min, and the ball-milling time is 4 - 6 h.

[0045] Step S7, adding a binder and a plasticizer to the obtained slurry and performing high-energy ball milling to obtain a uniformly mixed casting slurry.

[0046] In an optional embodiment, the binder is at least one of dibutyl polyvinyl alcohol, polyethylene glycol, polyvinyl alcohol, preferably dibutyl polyvinyl alcohol; the plasticizer is at least one of dioctyl phthalate, polyethylene glycol, dibutyl phthalate, preferably dioctyl phthalate.

[0047] Step S8, casting the obtained casting slurry and coating it on a PET film to obtain a green film.

[0048] In an optional embodiment, the casting rate is 8 - 10 mm / s; the thickness of the green film is 0.010 - 0.015 mm.

[0049] Step S9, leaving the obtained green film to dry at room temperature for 4 - 6 h.

[0050] Step S10, cutting the obtained green films with different x values respectively to obtain green film pieces, stacking the green film pieces with each x value to form a group layer, and then stacking the group layers together in the order of the gradient change of the x value. After stacking, pressing the stack into a compact blank with a hot press, and performing debinding on the blank to obtain a binder-free blank.

[0051] In an optional embodiment, the obtained green films with different x values are respectively cut to obtain green film pieces, and then the green films are stacked in the form of 1 - 8 layers of green film pieces to form each group layer, and then the group layers are stacked together in the order of the gradient change of the BiScO doping amount, as shown in 3 shown. After stacking, pressing into a blank at 65 - 70 °C and 65 - 75 MPa, and then cutting into a square blank with a side length of 13 mm. Performing debinding on the obtained blank to obtain a binder-free blank. Figure 1 shown. After stacking, pressing into a blank at 65 - 70 °C and 65 - 75 MPa, and then cutting into a square blank with a side length of 13 mm. Performing debinding on the obtained blank to obtain a binder-free blank.

[0052] The temperature of the debinding is 650 - 700 °C, the holding time is 6 - 8 h, and the rate is 0.5 - 1 °C / min.

[0053] Step S10: Sinter the debinded green body.

[0054] In an alternative embodiment, the sintering parameters include: first heating at a heating rate of 3 - 4 °C / min to 1000 - 1050 °C, and then heating at a heating rate of 2 - 3 °C / min to 1100 °C - 1200 °C and holding for 2 - 2.5 h. In the present invention, the temperature of the muffle furnace is rapidly increased to 1000 °C first. On the one hand, it can save time. On the other hand, the temperature control at this stage does not need to be very precise. When the temperature rises above 1000 °C, the heating rate needs to be reduced. On the one hand, if the heating rate is too fast, it is easy to cause the temperature to exceed the required 1100 °C - 1200 °C, and the too-fast heating rate will make the grain growth rate too fast, which is not conducive to the removal of pores, resulting in uneven pore distribution and affecting the densification of the ceramic, causing problems with the product. On the other hand, it can extend the service life of the sintering furnace.

[0055] Step S12: Coat silver electrodes on two surfaces of the sintered ceramic, hold at 650 - 700 °C for 30 - 60 min, and then polarize in high-temperature silicone oil at 100 - 120 °C.

[0056] In an alternative embodiment, the polarization electric field is 20 - 30 kV / cm and the time is 20 - 30 min.

[0057] The tape-casting preparation method of the composition-gradient lead lanthanum zirconate titanate-based pyroelectric ceramic provided by the present invention is an important method for preparing thin-film ceramics. It can be prepared from industrial raw materials, and the preparation process is stable. It can be mass-produced using equipment, which is convenient for industrial production.

[0058] The following further gives examples to illustrate the present invention in detail. It should be understood that the following examples are only used to further illustrate the present invention and cannot be construed as limiting the protection scope of the present invention. Those skilled in the art's non-essential improvements and adjustments based on the above content of the present invention all fall within the protection scope of the present invention. The specific process parameters and the like in the following examples are also only an example within a suitable range, that is, those skilled in the art can make selections within a suitable range according to the description herein, rather than being limited to the specific values in the following examples.

[0059] Example 1

[0060] In this Example 1, the preparation method of the pyroelectric ceramic green film with the chemical composition of (Pb 0.985 La 0.01 )(Zr 0.93 Ti 0.07 )O 3 (x = 0) is as follows: (1) Weigh 68.069 g of Pb 3 O 4 , 0.477 g of La 2 O 3 , 33.617 g of ZrO 2 , and 1.647 g of TiO 2 as raw materials for batching. Using anhydrous ethanol as the medium, ball mill for 4 h in a planetary ball mill and then dry at 80 °C for 5 h to obtain a uniformly mixed dry powder. Then, pre-calcine the obtained dry powder at 850 °C for 2 h to obtain the first powder; (2) Using anhydrous ethanol as the medium, ball mill the obtained first powder in a planetary ball mill for a second time for 6 h and then dry at 80 °C for 5 h to obtain the second powder; (3) Add the obtained second powder to anhydrous ethanol and ethyl acetate and perform high-energy ball milling for 2 h to obtain a uniformly dispersed slurry. Add polyvinyl alcohol dibutyl ester and dioctyl phthalate to the slurry and perform high-energy ball milling for another 2 h to obtain a uniformly mixed slurry. Pass the slurry through a casting machine to form a green film with a thickness of 0.010 - 0.012 mm. Leave the obtained green film at room temperature for 5 h to dry.

[0061] Example 2

[0062] In this Example 2, the chemical composition is 0.996 (Pb 0.985 La 0.01 )(Zr 0.93 Ti 0.07 )O 3 -0.004BiScO 3 (x = 0.004). The preparation method of the pyroelectric ceramic green film is referred to Example 1, with the only difference being that the mass of the raw materials is weighed according to the chemical formula in Example 2.

[0063] Example 3

[0064] In this Example 3, the chemical composition is 0.992 (Pb 0.985 La 0.01 )(Zr 0.93 Ti 0.07 )O 3 -0.008BiScO 3 (x = 0.008). The preparation method of the pyroelectric ceramic green film is referred to Example 1, with the only difference being that the mass of the raw materials is weighed according to the chemical formula in Example 3.

[0065] Example 4

[0066] In this Example 4, the chemical composition is 0.988 (Pb 0.985 La 0.01 )(Zr 0.93 Ti 0.07)O 3 -0.012BiScO 3 (x = 0.012) The preparation method of the pyroelectric ceramic green film refers to Example 1, with the only difference being that the raw materials are weighed according to the chemical formula in Example 4.

[0067] Example 5

[0068] Example 5 is to laminate and press the green films obtained in the above Examples 1-4, and then degrease and sinter them: (1) Cut the dried green films obtained in Examples 1-4, stack the thin slices of Examples 1-4 separately with 8 layers, and then stack them together in the order of Example 1, Example 2, Example 3, and Example 4. Finally, the layer ratio of Example 1, Example 2, Example 3, and Example 4 is 1:1:1:1, and press them into a square blank with a side length of 13 mm on a hot press at a temperature of 75 °C; then degrease the blank, and heat the degreased ceramic blank in a muffle furnace to 1000 °C at a heating rate of 3 °C / min, and then to 1100 °C at a heating rate of 2 °C / min, hold for 2 h, and then cool to room temperature with the furnace; (2) Coat silver electrodes on both surfaces of the sintered ceramic sample, and keep it at 650 °C for 30 min for standby; (3) Put the ceramic sample coated with silver electrodes into 120 °C silicone oil for polarization, with a polarization electric field of 20 kV / cm and a polarization time of 20 min.

[0069] Example 6

[0070] In this Example 6, the preparation method of the composition gradient laminated pyroelectric ceramic refers to Example 5, with the only difference being that the lamination order is stacked together in the order of Example 2, Example 1, Example 3, and Example 4. Finally, the layer ratio of Example 1, Example 2, Example 3, and Example 4 is 1:1:1:1, and a well-polarized ceramic is prepared.

[0071] Example 7

[0072] In this Example 7, the preparation method of the composition gradient laminated pyroelectric ceramic refers to Example 5, with the only difference being that the lamination order is stacked together in the order of Example 2, Example 3, Example 1, and Example 4. Finally, the layer ratio of Example 1, Example 2, Example 3, and Example 4 is 1:1:1:1, and a well-polarized ceramic is prepared.

[0073] Example 8

[0074] The preparation method of the composition gradient laminated pyroelectric ceramic in Example 8 refers to Example 5, with the only difference being that the lamination sequence is stacked together in the order of Example 2, Example 3, Example 4, and Example 1. Finally, the layer ratio of Example 1, Example 2, Example 3, and Example 4 is 1:1:1:1, and a well-polarized ceramic is prepared.

[0075] The room-temperature electrical properties of the composition gradient laminated pyroelectric ceramics in Examples 5-8 of the present invention are shown in Table 1 below. Among them, "0-4-8-12" means that the component layers are stacked together in the order of BiScO 3 Doping amounts are: 0, 0.004, 0.008, 0.012 stacked together in sequence; "4-0-8-12" means that the component layers are stacked together in the order of BiScO 3 Doping amounts are: 0.004, 0, 0.008, 0.012 stacked together in sequence; "4-8-0-12" means that the component layers are stacked together in the order of BiScO 3 Doping amounts are: 0.004, 0.008, 0, 0.012 stacked together in sequence; "4-8-12-0" means that the component layers are stacked together in the order of BiScO 3 Doping amounts are: 0.004, 0.008, 0.012, 0 stacked together in sequence; ε r is the dielectric constant, tanδ is the dielectric loss, d 33 is the piezoelectric constant, p is the pyroelectric coefficient at the phase transition, F i is the pyroelectric current response figure of merit factor, F v is the pyroelectric voltage response figure of merit factor, F d is the detectivity figure of merit factor, and ΔT is the phase transition temperature range.

[0076] Table 1:

[0077] As can be seen from Table 1, the pyroelectric performance of the gradient laminated pyroelectric ceramics is improved in the range of 30-50 °C. The pyroelectric peak is between 41-53 (10 -8 C / cm 2 ·K), and the dielectric loss also remains between 0.01-0.02. Different lamination sequences affect the pyroelectric performance to a certain extent. For Example 5 with an increasing content of equi-gradient BiScO 3 , the highest piezoelectric constant (d 33 = 90 pC / N) is achieved, and the dielectric constant is also the highest among the four lamination sequences (ε r = 360). In Example 7, the highest pyroelectric coefficient (53.81*10 -8 C / cm 2 ·K) and the detectivity figure of merit factor (F i = 2.1 10-7 m / V, F v = 78.57 m 2 / C, F d = 4.15 10 -2 ·Pa -1 / 2 )。Thus, it can be seen that the preparation of gradient laminates corresponding to different transition-type phase change temperature components by the casting method realizes the improvement of pyroelectric performance in a wide temperature range from room temperature to 50 °C, and different laminate sequences have a certain influence on the pyroelectric performance.

[0078] Figure 3 This is the polarization intensity vs. temperature curve of the composition gradient laminate pyroelectric ceramic of Example 5 of the present invention. As can be seen from the figure, the ferroelectric hysteresis loop is not opened at room temperature. As the temperature rises to 80 °C, it promotes the flipping of dipoles across the energy barrier and makes it easier for them to be oriented along the electric field direction, thus forming a ferroelectric hysteresis loop characteristic of the ferroelectric phase. At this time, the remanent polarization intensity reaches ~35 μC / cm 2 , indicating that a stable ferroelectric phase is induced by temperature, with a high remanent polarization intensity, and it is expected to obtain better pyroelectric performance.

[0079] Figure 4 This is the polarization intensity vs. temperature curve of the composition gradient laminate pyroelectric ceramic of Example 6 of the present invention. As can be seen from the figure, the ferroelectric hysteresis loop is not opened at room temperature. As the temperature rises to 100 °C, it promotes the flipping of dipoles across the energy barrier and makes it easier for them to be oriented along the electric field direction, thus forming a ferroelectric hysteresis loop characteristic of the ferroelectric phase. At this time, the remanent polarization intensity reaches ~33 μC / cm 2 , indicating that a stable ferroelectric phase is induced by temperature, with a high remanent polarization intensity, and it is expected to obtain better pyroelectric performance.

[0080] Figure 5 This is the polarization intensity vs. temperature curve of the composition gradient laminate pyroelectric ceramic of Example 7 of the present invention. As can be seen from the figure, the ferroelectric hysteresis loop is not opened at room temperature. As the temperature rises to 100 °C, it promotes the flipping of dipoles across the energy barrier and makes it easier for them to be oriented along the electric field direction, thus forming a ferroelectric hysteresis loop characteristic of the ferroelectric phase. At this time, the remanent polarization intensity reaches ~33 μC / cm 2 , indicating that a stable ferroelectric phase is induced by temperature, with a high remanent polarization intensity, and it is expected to obtain better pyroelectric performance.

[0081] Figure 6 This is the polarization intensity vs. temperature curve of the composition gradient laminate pyroelectric ceramic of Example 8 of the present invention. As can be seen from the figure, the ferroelectric hysteresis loop is not opened at room temperature. As the temperature rises to 100 °C, it promotes the flipping of dipoles across the energy barrier and makes it easier for them to be oriented along the electric field direction, thus forming a ferroelectric hysteresis loop characteristic of the ferroelectric phase. At this time, the remanent polarization intensity reaches ~33 μC / cm 2, indicating that the temperature-induced formation of a stable ferroelectric phase with a high remanent polarization is expected to obtain better pyroelectric properties.

[0082] Figure 7 This is the curve of the relative permittivity of the composition gradient laminated pyroelectric ceramics of Examples 5, 6, 7, and 8 of the present invention varying with temperature in the range of room temperature to 300 °C. As can be seen from the figure, the Curie temperatures of the gradient ceramics with different lamination orders are all around 215 °C, and at 100 °C, a step peak appears in the permittivity, which is related to the temperature-induced antiferroelectric-ferroelectric phase transition.

[0083] Figure 8 This is the curve of the pyroelectric coefficient of the composition gradient laminated pyroelectric ceramics of Examples 5, 6, 7, and 8 of the present invention varying with temperature. As can be seen from the figure, the gradient laminated ceramics prepared based on the tape casting method all achieve an improvement in pyroelectric performance in the range of 30 - 50 °C, and the pyroelectric peak is between 41 - 53×10 -8 C / cm 2 ·K. Different lamination orders affect the pyroelectric performance to a certain extent. Example 7 (3#) achieves the highest pyroelectric coefficient (53.81×10 -8 C / cm 2 ·K). Thus, it can be seen that the gradient lamination corresponding to different transition phase change temperature components prepared by the tape casting method realizes the improvement of pyroelectric performance in the wide temperature range of room temperature to 50 °C, and different lamination orders have a certain impact on the pyroelectric performance.

[0084] Figure 9 This is the curve of the figure of merit of the composition gradient laminated pyroelectric ceramics of Examples 5, 6, 7, and 8 of the present invention varying with temperature. As can be seen from the figure, the gradient laminated ceramics prepared based on the tape casting method all achieve an improvement in pyroelectric performance and the figure of merit factor in the wide temperature range (30 - 50 °C). For example, its current response factor F i is increased to 1.6 - 2.1×10 -7 m / V, the voltage response factor F v is increased to 50 - 78.57 m 2 / C, and the detectivity factor F d is increased to 3 - 4×10 -2 ·Pa -1 / 2 . At the same time, different lamination orders also have a certain impact on the pyroelectric performance. For Example 7 (3#), the maximum voltage response factor F v (78.57 m 2 / C) and the detectivity factor F d (4.15×10 -2 ·Pa -1 / 2 ) are achieved.

[0085] Comparative Example 1

[0086] In this Comparative Example 1, the chemical composition is 0.984(Pb 0.985 La 0.01 )(Zr 0.93 Ti 0.07 )O 3 -0.016BiScO 3 (x = 0.016). The preparation method of the pyroelectric ceramic green film was referred to Example 1, with the only difference being that: the raw materials were weighed according to the chemical formula in Comparative Example 1; then the obtained dried green film was cut, and then the thin slices were laminated (the number of layers was 8 layers), and after pressing, debinding and sintering, the pyroelectric ceramic was obtained.

[0087] Figure 10 (a) is the curve of the dielectric constant of the pyroelectric ceramic with x = 0.016 changing with temperature. As can be seen from the figure, when x = 0.016, a step peak appears in the dielectric constant near 100 °C, which is related to the temperature-induced antiferroelectric-ferroelectric phase transition. At the same time, a ferroelectric hysteresis loop with ferroelectric characteristics also appears in the temperature-variable hysteresis loop, verifying the temperature-induced antiferroelectric-ferroelectric phase transition (b). (d) is the curve of the pyroelectric coefficient of the pyroelectric ceramics prepared from the green films of Examples 1-4 and Comparative Example 1 changing with temperature. As can be seen from the figure, compared with the pyroelectric ceramics of the compositions of Examples 1-4 (x = 0, 0.004, 0.008, 0.012), the pyroelectric coefficient of the pyroelectric ceramic in Comparative Example 1 (x = 0.016) < 1×10 -8 C / cm 2 ·K, indicating that the pyroelectric ceramic of this composition has no pyroelectric performance. The pyroelectric ceramics of the compositions of Examples 1-4 (x = 0, 0.004, 0.008, 0.012) are in a stable ferroelectric phase after electric field polarization, while the pyroelectric ceramic of the x = 0.016 composition undergoes a ferroelectric-antiferroelectric phase transition immediately after electric field polarization and the removal of the electric field. The internal polarization intensity is zero, there is no bound charge on the surface, and there is no thermal current output and no pyroelectric signal after thermal perturbation, indicating that x = 0.016 is not suitable for preparing the composition gradient laminated pyroelectric ceramic of the present invention.

Claims

1. A wide temperature range component gradient laminated pyroelectric ceramic, characterized in that: The wide temperature range component gradient laminated pyroelectric ceramic is composed of multiple component layers, and the chemical composition formula of each component layer is: (1-x)(Pb 0.985 La 0.01 )(Zr 0.93 Ti 0.07 )O3-xBiScO3, wherein x is the molar fraction of the component BiScO3, 0≤x≤0.012; and x varies in a gradient between multiple component layers.

2. The wide temperature range composition gradient laminated pyroelectric ceramic according to claim 1, characterized in that: The gradient of the x value between two adjacent component layers in the plurality of component layers is 0-0.

012. Preferably, the gradient of the x value of the plurality of component layers increases gradually.

3. The wide temperature range composition gradient laminated pyroelectric ceramic according to claim 1 or 2, characterized in that: Each component layer is composed of 2 to 8 layers of thin sheets stacked together; the thickness of each layer of thin sheet is 0.010 to 0.015 mm.

4. The wide temperature range composition gradient laminated pyroelectric ceramic according to any one of claims 1 to 3, characterized in that: The wide temperature range component gradient laminated pyroelectric ceramic has a relative dielectric constant of 300 to 360 at 25°C and a test frequency of 1kHz, and a pyroelectric coefficient p of 40 to 54×10 -8 C cm -2 ·K -1 , current response figure of merit F i 1.5~2.2×10 -7 m / V, voltage response figure of merit F v 50~80m 2 / C, Detection rate merit factor F d 2~5×10 -2 Pa -1 / 2 .

5. A method for preparing a wide temperature range component gradient laminated pyroelectric ceramic according to any one of claims 1 to 4, characterized in that: include: (1) according to the molar percentage of the chemical composition formula, using analytically pure Pb3O4, La2O3, ZrO2, TiO2, Bi2O3 and Sc2O5 as raw materials and anhydrous ethanol as a medium, a first ball milling is performed to obtain a wet powder slurry; (2) drying and pre-sintering the obtained wet powder slurry to obtain a first powder; (3) ball milling the obtained first powder for a second time using anhydrous ethanol as a medium, and drying the wet powder obtained after the second ball milling to obtain a second powder; (4) adding a solvent and a dispersant to the obtained second powder and performing high-energy ball milling to obtain a uniformly dispersed slurry, and adding a binder and a plasticizer to the slurry and performing high-energy ball milling to obtain a uniformly mixed casting slurry; (5) The obtained casting slurry is cast on a PET film by a casting machine to obtain a raw film, and then placed at room temperature for 4 to 6 hours to dry; (6) Cut the prepared raw films with different x values ​​into raw film sheets, and stack the raw film sheets with different x values ​​to form component layers, and then stack the component layers together in the order of the gradient change of the x values. After stacking, use a hot press to press them into a compact embryo, debind the embryo to obtain a binder-free embryo, and sinter the debinded embryo.

6. The preparation method according to claim 5, characterized in that: The parameters of the first ball milling in step (1) and / or the second ball milling in step (3) include: the grinding balls are zirconium oxide balls; the mass ratio of the ball milling raw material, the grinding balls and the ball milling solvent is 1: (9-10): (4-5); the diameter ratio of the grinding balls is 0.8-1 mm, and the mass ratio is 1: (1-2): (1-2); The drying temperature is 80-100° C. and the drying time is 4-6 hours.

7. The preparation method according to claim 5 or 6, characterized in that: In step (2), the pre-sintering temperature is 800-850° C., the holding time is 2-3 hours, and the heating rate is 1.5-2° C. / min.

8. The preparation method according to any one of claims 5 to 7, characterized in that: In step (4), the parameters of the high-energy ball mill are: the ball mill is a nylon mill and the ball mill is a ZrO2 ball; the solvent is anhydrous ethanol and ethyl acetate, and the mass ratio is (2-3): (1-1.5); the dispersant is a polyethylene oxide functional polymer or tributyl phosphate, preferably a polyethylene oxide functional polymer; the binder is at least one of polyvinyl dibutyl alcohol, polyethylene glycol, and polyvinyl alcohol; the plasticizer is at least one of dioctyl phthalate, polyethylene glycol, and dibutyl phthalate.

9. The preparation method according to any one of claims 5 to 8, characterized in that: In step (5), the casting rate is 8 to 10 mm / s; the thickness of the obtained raw film is 0.010 to 0.015 mm.

10. The preparation method according to any one of claims 5 to 9, characterized in that: In step (6), the debinding parameters include: the debinding temperature is 650-700°C, the holding time is 6-8h, and the heating rate is 0.5-1°C / min; The sintering parameters include: firstly heating the temperature to 1000-1050° C. at a heating rate of 3-4° C. / min, then heating the temperature to 1100-1200° C. at a heating rate of 2-3° C. / min, and keeping the temperature for 2-2.5 hours.

11. The preparation method according to any one of claims 5 to 10, characterized in that: After the green body is sintered, the method further includes: applying silver electrodes on the two surfaces of the sintered ceramic, placing the ceramic in a muffle furnace, heating the temperature to 650-700°C at a heating rate of 2-3°C / min and keeping the temperature for 30-60min, and then polarizing the ceramic in 100-120°C silicone oil; wherein the polarization electric field is 20-30kV / cm and the polarization time is 20-30min.

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