PZT-based composite film with wide-temperature-range negative electrocaloric effect and preparation method of PZT-based composite film

Abstract

The invention belongs to the technical field of electronic functional materials and devices, and particularly relates to a PZT-based composite film with a wide-temperature-range negative electrocaloric effect, the PZT-based composite film with the wide-temperature-range negative electrocaloric effect is obtained by alternately overlapping a TiO2 component layer, an Hf0. 5Zr0. 5O2 component layer, a PbO component layer and a PbZrxTi1-xO3 component layer in sequence, x represents a mole fraction and is larger than or equal to 0.20 and smaller than or equal to 0.60, and each component layer is a single-layer sheet or is formed by overlapping multiple layers of sheets. The invention also provides a preparation method of the PZT-based composite film. According to the method disclosed by the invention, the large electrocaloric effect is effectively excited by regulating and controlling the defect dipole, so that the PZT-based composite film has the effect of the negative electrocaloric effect in a wide temperature range.

Description

Technical Field

[0001] This invention belongs to the field of electronic functional materials and devices, specifically relating to a PZT-based composite thin film with a wide temperature range negative electrocaloric effect and its preparation method. Background Technology

[0002] With the continuous development of modern industry and the improvement of people's living standards, the demand for efficient and environmentally friendly refrigeration technology is becoming increasingly prominent. In particular, the rapid development of technologies such as 5G / 6G communication and artificial intelligence has led to a surge in device power density, making localized overheating a key bottleneck restricting performance improvement. Traditional vapor compression cycle refrigeration technology consumes a large amount of electricity, and the refrigerants used cause serious environmental damage. Meanwhile, traditional air-cooling and liquid-cooling technologies are limited by size, noise, and integration, making it difficult to meet the thermal management requirements of integrated chip-level systems. Solid-state refrigeration technology based on the electrocaloric effect (ECE), with its advantages of miniaturization, fast response, energy saving, and environmental friendliness, is considered the core direction of next-generation efficient refrigeration solutions.

[0003] Ferroelectric materials are materials that exhibit spontaneous polarization within a certain temperature range, and whose polarization intensity reverses with the application of an external electric field. As novel electronic functional materials, ferroelectric materials possess excellent ferroelectric, pyroelectric, and dielectric properties, and their highly efficient electrocaloric effect holds broad application prospects in the field of solid-state refrigeration. The electrocaloric effect is the phenomenon in which ferroelectric materials exhibit reversible entropy and temperature changes when an external electric field is applied or removed. It is mainly achieved by altering the order of the dipoles through changes in the external electric field, thereby changing entropy and temperature and achieving the purpose of refrigeration. The electrocaloric effect includes the positive electrocaloric effect (ΔT > 0) and the negative electrocaloric effect (ΔT < 0). Among them, the negative electrocaloric effect can achieve energy recovery and efficiency improvement in specific refrigeration cycles, and has important application value.

[0004] Compared to bulk ferroelectric ceramics, ferroelectric thin films, due to their higher breakdown field strength and dielectric properties, are more likely to achieve a large electrocaloric effect. Currently, lead zirconate titanate (PZT) thin films are widely researched and applied in the field of electrocaloric refrigeration technology. However, according to existing research and reports, single PZT ferroelectric thin films generally exhibit a positive electrocaloric effect with a large ΔT. Therefore, if it is possible to achieve both positive and negative electrocaloric effects and a negative electrocaloric effect over a wide temperature range by designing the composition of PZT thin films and controlling the process parameters, it will effectively improve their refrigeration efficiency and is of great significance for the development of high-efficiency electrocaloric refrigeration materials. Therefore, researching and developing a PZT-based composite thin film with a negative electrocaloric effect over a wide temperature range is very important. Summary of the Invention

[0005] This invention aims to solve the above-mentioned technical problems and provides a PZT-based composite film with a wide temperature range negative electrocaloric effect. This PZT-based composite film is produced by introducing TiO2 and Hf into a single PZT film using a sol-gel method. 0.5 Zr 0.5 The method of this invention is prepared by combining O2 and PbO. By controlling the defect dipole, the large electrocaloric effect is effectively excited, so that the PZT-based composite film has a wide temperature range negative electrocaloric effect.

[0006] The technical solution of this invention is as follows:

[0007] A PZT-based composite thin film exhibiting a wide-temperature-range negative electrocaloric effect, comprising sequentially TiO2 component layers, Hf... 0.5 Zr 0.5 O2 component layer, PbO component layer and PbZr x Ti 1-x The O3 component layers are obtained by alternating layers, where x represents the mole fraction, 0.20 ≤ x ≤ 0.60, and each component layer is either a single-layer thin sheet or composed of multiple layers of thin sheets.

[0008] Preferably, the PZT-based composite film of the present invention consists of, sequentially, one TiO2 component layer and three PbZr layers. x Ti 1-x O3 component layer, 2-layer Hf 0.5 Zr 0.5 O2 component layer, 3-layer PbZr x Ti 1-x O3 component layer, 1 layer of PbO component layer and 6 layers of PbZr x Ti 1-x The O3 components are stacked in layers, preferably with a thickness of 10-50 nm for each layer.

[0009] Preferably, the present invention also provides a method for preparing the PZT-based composite thin film with a wide temperature range negative electrocaloric effect, comprising the following steps:

[0010] (1) Drop TiO2 colloid onto the substrate, perform film deposition, dry, pyrolyze, anneal in air atmosphere to crystallize, and repeat this step 0-5 times to obtain a thin film containing TiO2 component layer;

[0011] (2) PbZr is dropped onto the film containing TiO2 component layer obtained in step (1). x Ti 1-x O3 colloid is coated, dried, pyrolyzed, and annealed in air to crystallize. This step is repeated 0-5 times to obtain a PbZr-containing product. x Ti 1-x Thin film I of O3 component layer;

[0012] (3) The PbZr-containing sample obtained in step (2) x Ti 1-x Hf was dropped onto the thin film I of the O3 component layer. 0.5 Zr 0.5 O2 colloid is coated, dried, pyrolyzed, and annealed in air to crystallize. This step is repeated 0-5 times to obtain a product containing Hf. 0.5 Zr 0.5 Thin film of O2 component layer;

[0013] (4) The Hf-containing sample obtained in step (3) 0.5 Zr 0.5 PbZr was dropped onto the O2 component layer film. x Ti 1-x O3 colloid is coated, dried, pyrolyzed, and annealed in air to crystallize. This step is repeated 0-5 times to obtain a PbZr-containing product. x Ti 1-x Thin film II with O3 component layer;

[0014] (5) The PbZr-containing sample obtained in step (4) x Ti 1-x PbO colloid was dropped onto the thin film II containing the O3 component layer, and the film was deposited, dried, pyrolyzed, and annealed in air to crystallize. This step was repeated 0-5 times to obtain a thin film containing the PbO component layer.

[0015] (6) PbZr is dropped onto the thin film containing the PbO component layer obtained in step (5). x Ti 1-x O3 colloid is coated, dried, pyrolyzed, and annealed in air to crystallize. This step is repeated 0-5 times to obtain a PbZr-containing product. x Ti 1-x Thin film III with O3 component layer is obtained, which is a PZT-based composite film with a wide temperature range negative electrocaloric effect.

[0016] Preferably, the steps (1)-(6) mentioned in the method of the present invention, namely coating, drying, pyrolysis, and annealing in air atmosphere for crystallization, are as follows: coating is performed by spin coating at a speed of 2000-6000 rpm for 25-35 s using a spin coater, drying at 200-400 ℃ for 2-10 min to remove moisture, then pyrolysis at 400-600 ℃ for 2-10 min to remove organic matter, and finally annealing in air atmosphere at 700-800 ℃ for 2-10 min for crystallization.

[0017] Preferably, the method for preparing the TiO2 colloid in the method of the present invention is as follows:

[0018] (1) Mix glacial acetic acid and CH3COCH2COCH3 at a volume ratio of 1:2-4 to obtain a mixed solution;

[0019] (2) At room temperature, Ti(OC4H9)4 raw material is dissolved in the mixture, stirred for 0.5-1 h, and aged for 12-36 h to obtain TiO2 colloid with a concentration of 0.2-0.3 mol / L.

[0020] Preferably, the PbZr described in the method of the present invention x Ti 1-x The preparation method of O3 colloid is as follows:

[0021] (1) Using Pb(CH3COO)2·3H2O, Ti(OC4H9)4 and Zr(OC3H7)4 as raw materials, according to PbZr x Ti 1-x The chemical composition of O3 is determined by weighing the raw materials, where 0.2 ≤ x ≤ 0.60;

[0022] (2) Mix glacial acetic acid and CH3COCH2COCH3 at a volume ratio of 1:2-4 to obtain mixture I;

[0023] (3) Dissolve the raw material Pb(CH3COO)2·3H2O in glacial acetic acid at 100-150 °C at a concentration of 0.7-0.9 mol / L to obtain mixture II;

[0024] (4) At room temperature, the raw material Ti(OC4H9)4 was dissolved in mixed solution I at a concentration of 0.7-0.9 mol / L, and then the raw material Zr(OC3H7)4 was added to continue dissolving to obtain mixed solution III;

[0025] (5) Mix the obtained mixture II and mixture III completely, add mixture I for concentration correction, stir for 0.5-1 h, and let it age for 12-36 h to obtain PbZr with a concentration of 0.2-0.3 mol / L. x Ti 1-x O3 colloid.

[0026] Preferably, the Hf in the method of the present invention 0.5 Zr 0.5 The preparation method of O2 colloid is as follows:

[0027] (1) Mix glacial acetic acid and CH3COCH2COCH3 at a volume ratio of 1:2-4 to obtain a mixed solution;

[0028] (2) According to Hf 0.5 Zr 0.5 The chemical composition of O2 is determined by weighing C8H. 20HfO4 and Zr(OC3H7)4, and C8H 20 HfO4 and Zr(OC3H7)4 were dissolved in a mixed solution at room temperature, stirred for 0.5–1 h, and aged for 12–36 h to obtain HfO4 with a concentration of 0.2–0.3 mol / L. 0.5 Zr 0.5 O2 colloid.

[0029] Preferably, the method for preparing the PbO colloid in the method of the present invention is as follows:

[0030] (1) Mix glacial acetic acid and CH3COCH2COCH3 at a volume ratio of 1:2-4 to obtain a mixed solution;

[0031] (2) Dissolve the raw material Pb(CH3COO)2·3H2O in the mixed solution at 100-150 °C, stir for 0.5-1 h, and let it age for 12-36 h to obtain PbO colloid with a concentration of 0.2-0.3 mol / L.

[0032] Preferably, in the method of the present invention, step (1) is repeated 0 times to obtain a thin film containing one TiO2 component layer; step (2) is repeated 2 times to obtain a thin film containing three PbZr components. x Ti 1-x O3 component layer thin film I; Step (3) is repeated once more to obtain a thin film containing 2 Hf layers. 0.5 Zr 0.5 The O2 component layer thin film; step (4) is repeated twice to obtain a thin film containing three layers of PbZr. x Ti 1-x Thin film II with O3 component layer; Step (5) is repeated 0 times to obtain a thin film with 1 PbO component layer; Step (6) is repeated 5 times to obtain a thin film with 6 PbZr components. x Ti 1-x Thin film III with O3 component layer.

[0033] Due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows:

[0034] 1. This invention uses TiO2 and Hf 0.5 Zr 0.5 By layering O2, PbO and PZT, and through a specific layer structure arrangement, the defect dipoles were precisely controlled, and a negative electrocaloric effect over a wide temperature range was successfully excited, solving the technical problem that a single PZT film could only achieve a positive electrocaloric effect.

[0035] 2. The PZT-based composite thin film of the present invention has a negative electrocaloric effect operating temperature range of 180 K and above, a negative adiabatic temperature change ΔT > 10.7 K, an adiabatic entropy change ΔS > 6.2 K, and has both positive and negative electrocaloric effects, which greatly improves the refrigeration efficiency and can meet the needs of diverse refrigeration scenarios.

[0036] 3. The method of the present invention, through the sol-gel method combined with precise process parameter control, produces PZT-based composite films with high purity, good density, small average grain size, high electric field breakdown strength, and strong structural stability and reliability.

[0037] 4. The sol-gel method used in this invention is simple to operate and has low cost. Various process parameters (such as colloid concentration, spin coating speed, drying, pyrolysis, annealing temperature and time, etc.) can be precisely controlled, making it easy to scale up production and with broad industrial application prospects. Attached Figure Description

[0038] Figure 1 This is a scanning electron microscope image of the cross-section of the PZT-based composite film prepared in Example 1 of the present invention.

[0039] Figure 2 The figure shows the adiabatic temperature change (ΔT) diagram (i.e., the electrical performance diagram) of the PZT-based composite film prepared in Example 1 of this invention as a function of temperature. The inset is the adiabatic entropy change (ΔS) diagram. Detailed Implementation

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Example 1

[0042] A PZT-based composite thin film exhibiting a wide-temperature-range negative electrocaloric effect consists of a TiO2 component layer and three PbZr components. 0.3 Ti 0.7 O3 component layer, 2-layer Hf 0.5 Zr 0.5 O2 component layer, 3-layer PbZr 0.3 Ti 0.7 O3 component layer, 1 layer of PbO component layer and 6 layers of PbZr 0.3 Ti 0.7 The O3 components are stacked in layers, with each layer having a thickness of 10-50 nm.

[0043] The above method for preparing PZT-based composite films includes the following steps:

[0044] (1) TiO2 colloid is dropped onto a substrate, coated, dried, pyrolyzed, and annealed in air to crystallize, resulting in a thin film containing a TiO2 component layer;

[0045] (2) PbZr is dropped onto the thin film containing one TiO2 component layer obtained in step (1). 0.3 Ti 0.7 O3 colloid was coated, dried, pyrolyzed, and annealed in air to crystallize. This step was repeated twice to obtain a PbZr layer containing three layers. 0.3 Ti 0.7 Thin film I of O3 component layer;

[0046] (3) The PbZr layer obtained in step (2) contains 3 layers 0.3 Ti 0.7 Hf was dropped onto the thin film I of the O3 component layer. 0.5 Zr 0.5 O2 colloid is coated, dried, pyrolyzed, and annealed in air to crystallize. This step is repeated once to obtain a product containing two layers of Hf. 0.5 Zr 0.5 Thin film of O2 component layer;

[0047] (4) The Hf layer obtained in step (3) contains 2 layers 0.5 Zr 0.5 PbZr was dropped onto the O2 component layer film. 0.3 Ti 0.7 O3 colloid was coated, dried, pyrolyzed, and annealed in air to crystallize. This step was repeated twice to obtain a PbZr layer containing three layers. 0.3 Ti 0.7 Thin film II with O3 component layer;

[0048] (5) The PbZr layer obtained in step (4) contains 3 layers 0.3 Ti 0.7 PbO colloid was dropped onto the thin film II containing the O3 component layer, and the film was deposited, dried, pyrolyzed, and annealed in air to crystallize, thus obtaining a thin film containing one PbO component layer.

[0049] (6) PbZr is dropped onto the thin film containing one layer of PbO obtained in step (5). 0.3 Ti 0.7 O3 colloid was coated, dried, pyrolyzed, and annealed in air to crystallize. This process was repeated 5 times to obtain a PbZr layer containing 6 layers. 0.3 Ti 0.7 Thin film III with O3 component layer is obtained, which is a PZT-based composite film with a wide temperature range negative electrocaloric effect.

[0050] Scanning electron microscope (SEM) image of the cross-section of the PZT-based composite thin film described in Example 1 is shown below. Figure 1 As shown in the figure, the cross-section of the film is flat and dense, without obvious voids and cracks, and the thickness is ~690 nm. The film deposited on the substrate exhibits a columnar structure, which is due to the substrate having an inductive effect on the growth direction of the film, and the film grows along the preferred orientation.

[0051] The adiabatic temperature change (ΔT) diagram (i.e., electrical performance diagram) of the PZT-based composite film described in Example 1 is as follows: Figure 2 As shown, Figure 2 The inset shows the adiabatic entropy change (ΔS) diagram. ΔT and ΔS were obtained by measuring the temperature-varying PE hysteresis loop of the thin film within the temperature range of 303-523 K and calculating them according to Maxwell's relation. As can be seen from the figure, ΔT and ΔS of the thin film increase continuously with increasing electric field. Within the temperature range of 303-337 K, the polarization of the thin film decreases with increasing temperature, exhibiting a positive electrocaloric effect. The operating temperature range is narrow, only ~34 K, with the maximum ΔT and ΔS at 761.15 kV / cm being ~11.30 K and ~-11.19 K, respectively. Within the temperature range of 337-523 K, the polarization of the thin film increases with increasing temperature, exhibiting a negative electrocaloric effect. The maximum ΔT and ΔS at 761.15 kV / cm are ~10.73 K and ~6.24 K, respectively, and ΔT and ΔS continue to increase at the right end of the test temperature range (523 K), demonstrating an ultra-wide negative electrocaloric effect operating temperature range exceeding 180 K. Electrocaloric cooling materials experience temperature variations with ambient temperature during application; therefore, a wide operating temperature range expands their application scope. The negative electrocaloric effect arises because the composite of multi-component layers introduces lattice mismatch and differences in thermal expansion coefficients between different components, creating built-in stress at the film interfaces. Defect dipoles suppress domain wall movement through pinning effects. Simultaneously, a multiphase coexistence structure forms in the composite film. Differences in the responses of different phases under an electric field lead to local polarization reorientation or phase transitions, disrupting local polar order and resulting in significant entropy changes. In addition, the polarization of different component layers changes with temperature in different ways. Through interface coupling, polarization reversal or rearrangement can be achieved in different temperature ranges. Furthermore, the defect dipoles form an internal bias electric field, which makes the negative electrocaloric effect cover a wider operating temperature range and broaden the temperature window of the negative electrocaloric response.

[0052] The steps (1)-(6) mentioned above, namely coating, drying, pyrolysis, and annealing in air atmosphere for crystallization, are as follows: coating is performed by spin coating at 2000 rpm for 35 s using a spin coater, drying at 200 ℃ for 10 min to remove moisture, then pyrolysis at 400 ℃ for 10 min to remove organic matter, and finally annealing in air atmosphere at 700 ℃ for 10 min for crystallization.

[0053] The preparation method of the above TiO2 colloid is as follows:

[0054] (1) Mix glacial acetic acid and CH3COCH2COCH3 at a volume ratio of 1:2 to obtain a mixed solution;

[0055] (2) At room temperature, Ti(OC4H9)4 raw material was dissolved in the mixture, stirred for 0.5 h, and aged for 36 h to obtain TiO2 colloid with a concentration of 0.2 mol / L.

[0056] The above PbZr 0.3 Ti 0.7 The preparation method of O3 colloid is as follows:

[0057] (1) Using Pb(CH3COO)2·3H2O, Ti(OC4H9)4 and Zr(OC3H7)4 as raw materials, according to PbZr 0.3 Ti 0.7 The chemical composition of O3 is determined by weighing the raw materials;

[0058] (2) Mix glacial acetic acid and CH3COCH2COCH3 at a volume ratio of 1:2 to obtain mixture I;

[0059] (3) Dissolve the raw material Pb(CH3COO)2·3H2O in glacial acetic acid at 100 °C at a concentration of 0.8 mol / L to obtain mixture II;

[0060] (4) At room temperature, the raw material Ti(OC4H9)4 was dissolved in mixed solution I at a concentration of 0.8 mol / L, and then the raw material Zr(OC3H7)4 was added to continue dissolving to obtain mixed solution III;

[0061] (5) Mix the obtained mixture II and mixture III completely, add mixture I for concentration correction, stir for 0.5 h, and let it age for 36 h to obtain PbZr with a concentration of 0.2 mol / L. 0.3 Ti 0.7 O3 colloid.

[0062] The above Hf 0.5 Zr 0.5 The preparation method of O2 colloid is as follows:

[0063] (1) Mix glacial acetic acid and CH3COCH2COCH3 at a volume ratio of 1:2 to obtain a mixed solution;

[0064] (2) According to Hf 0.5 Zr 0.5 The chemical composition of O2 is determined by weighing C8H. 20 HfO4 and Zr(OC3H7)4, and C8H 20 HfO4 and Zr(OC3H7)4 were dissolved in a mixed solution at room temperature, stirred for 0.5 h, and aged for 36 h to obtain HfO4 with a concentration of 0.2 mol / L. 0.5 Zr 0.5 O2 colloid.

[0065] The preparation method of the above PbO colloid is as follows:

[0066] (1) Mix glacial acetic acid and CH3COCH2COCH3 at a volume ratio of 1:2 to obtain a mixed solution;

[0067] (2) Dissolve the raw material Pb(CH3COO)2·3H2O in the mixed solution at 100 °C, stir for 0.5 h, and let it age for 36 h to obtain PbO colloid with a concentration of 0.2 mol / L.

[0068] Example 2

[0069] A PZT-based composite thin film exhibiting a wide-temperature-range negative electrocaloric effect consists of a TiO2 component layer and three PbZr components. 0.2 Ti 0.8 O3 component layer, 2-layer Hf 0.5 Zr 0.5 O2 component layer, 3-layer PbZr 0.2 Ti 0.8 O3 component layer, 1 layer of PbO component layer and 6 layers of PbZr 0.2 Ti 0.8 The O3 components are stacked in layers, with each layer having a thickness of 10-50 nm.

[0070] The above method for preparing PZT-based composite films includes the following steps:

[0071] (1) TiO2 colloid is dropped onto a substrate, coated, dried, pyrolyzed, and annealed in air to crystallize, resulting in a thin film containing a TiO2 component layer;

[0072] (2) PbZr is dropped onto the thin film containing one TiO2 component layer obtained in step (1). 0.2 Ti 0.8O3 colloid was coated, dried, pyrolyzed, and annealed in air to crystallize. This step was repeated twice to obtain a PbZr layer containing three layers. 0.2 Ti 0.8 Thin film I of O3 component layer;

[0073] (3) The PbZr layer obtained in step (2) contains 3 layers 0.2 Ti 0.8 Hf was dropped onto the thin film I of the O3 component layer. 0.5 Zr 0.5 O2 colloid is coated, dried, pyrolyzed, and annealed in air to crystallize. This step is repeated once to obtain a product containing two layers of Hf. 0.5 Zr 0.5 Thin film of O2 component layer;

[0074] (4) The Hf layer obtained in step (3) contains 2 layers 0.5 Zr 0.5 PbZr was dropped onto the O2 component layer film. 0.2 Ti 0.8 O3 colloid was coated, dried, pyrolyzed, and annealed in air to crystallize. This step was repeated twice to obtain a PbZr layer containing three layers. 0.2 Ti 0.8 Thin film II with O3 component layer;

[0075] (5) The PbZr layer obtained in step (4) contains 3 layers 0.2 Ti 0.8 PbO colloid was dropped onto the thin film II containing the O3 component layer, and the film was deposited, dried, pyrolyzed, and annealed in air to crystallize, thus obtaining a thin film containing one PbO component layer.

[0076] (6) PbZr is dropped onto the thin film containing one layer of PbO obtained in step (5). 0.2 Ti 0.8 O3 colloid was coated, dried, pyrolyzed, and annealed in air to crystallize. This process was repeated 5 times to obtain a PbZr layer containing 6 layers. 0.2 Ti 0.8 Thin film III with O3 component layer is obtained, which is a PZT-based composite film with a wide temperature range negative electrocaloric effect.

[0077] The steps (1)-(6) mentioned above, namely coating, drying, pyrolysis, and annealing in air atmosphere for crystallization, are as follows: coating is performed by spin coating at 6000 rpm for 25 s using a spin coater, drying at 400 ℃ for 2 min to remove moisture, then pyrolysis at 600 ℃ for 2 min to remove organic matter, and finally annealing in air atmosphere at 800 ℃ for 2 min for crystallization.

[0078] The preparation method of the above TiO2 colloid is as follows:

[0079] (1) Mix glacial acetic acid and CH3COCH2COCH3 at a volume ratio of 1:3 to obtain a mixed solution;

[0080] (2) At room temperature, Ti(OC4H9)4 raw material was dissolved in the mixture, stirred for 1 h, and aged for 12 h to obtain TiO2 colloid with a concentration of 0.3 mol / L.

[0081] The above PbZr 0.2 Ti 0.8 The preparation method of O3 colloid is as follows:

[0082] (1) Using Pb(CH3COO)2·3H2O, Ti(OC4H9)4 and Zr(OC3H7)4 as raw materials, according to PbZr 0.2 Ti 0.8 The chemical composition of O3 is determined by weighing the raw materials;

[0083] (2) Mix glacial acetic acid and CH3COCH2COCH3 at a volume ratio of 1:3 to obtain mixture I;

[0084] (3) Dissolve the raw material Pb(CH3COO)2·3H2O in glacial acetic acid at 150 °C at a concentration of 0.9 mol / L to obtain mixture II;

[0085] (4) At room temperature, Ti(OC4H9)4 was dissolved in mixture I at a concentration of 0.9 mol / L, and Zr(OC3H7)4 was added to continue dissolving to obtain mixture III;

[0086] (5) Mix the obtained mixture II and mixture III completely, add mixture I for concentration correction, stir for 1 h, and let it age for 12 h to obtain PbZr with a concentration of 0.3 mol / L. 0.2 Ti 0.8 O3 colloid.

[0087] The above Hf 0.5 Zr 0.5 The preparation method of O2 colloid is as follows:

[0088] (1) Mix glacial acetic acid and CH3COCH2COCH3 at a volume ratio of 1:3 to obtain a mixed solution;

[0089] (2) According to Hf 0.5 Zr 0.5 The chemical composition of O2 is determined by weighing C8H. 20 HfO4 and Zr(OC3H7)4, and C8H 20HfO4 and Zr(OC3H7)4 were dissolved in a mixed solution at room temperature, stirred for 1 h, and aged for 12 h to obtain HfO4 with a concentration of 0.3 mol / L. 0.5 Zr 0.5 O2 colloid.

[0090] The preparation method of the above PbO colloid is as follows:

[0091] (1) Mix glacial acetic acid and CH3COCH2COCH3 at a volume ratio of 1:3 to obtain a mixed solution;

[0092] (2) Dissolve the raw material Pb(CH3COO)2·3H2O in the mixed solution at 150 °C, stir for 1 h, and let it age for 12 h to obtain PbO colloid with a concentration of 0.3 mol / L.

[0093] Example 3

[0094] A PZT-based composite thin film exhibiting a wide-temperature-range negative electrocaloric effect consists of a TiO2 component layer and three PbZr components. 0.6 Ti 0.4 O3 component layer, 2-layer Hf 0.5 Zr 0.5 O2 component layer, 3-layer PbZr 0.6 Ti 0.4 O3 component layer, 1 layer of PbO component layer and 6 layers of PbZr 0.6 Ti 0.4 The O3 components are stacked in layers, with each layer having a thickness of 10-50 nm.

[0095] The above method for preparing PZT-based composite films includes the following steps:

[0096] (1) TiO2 colloid is dropped onto a substrate, coated, dried, pyrolyzed, and annealed in air to crystallize, resulting in a thin film containing a TiO2 component layer;

[0097] (2) PbZr is dropped onto the thin film containing one TiO2 component layer obtained in step (1). 0.6 Ti 0.4 O3 colloid was coated, dried, pyrolyzed, and annealed in air to crystallize. This step was repeated twice to obtain a PbZr layer containing three layers. 0.6 Ti 0.4 Thin film I of O3 component layer;

[0098] (3) The PbZr layer obtained in step (2) contains 3 layers 0.6 Ti 0.4 Hf was dropped onto the thin film I of the O3 component layer. 0.5 Zr 0.5O2 colloid is coated, dried, pyrolyzed, and annealed in air to crystallize. This step is repeated once to obtain a product containing two layers of Hf. 0.5 Zr 0.5 Thin film of O2 component layer;

[0099] (4) The Hf layer obtained in step (3) contains 2 layers 0.5 Zr 0.5 PbZr was dropped onto the O2 component layer film. 0.6 Ti 0.4 O3 colloid was coated, dried, pyrolyzed, and annealed in air to crystallize. This step was repeated twice to obtain a PbZr layer containing three layers. 0.6 Ti 0.4 Thin film II with O3 component layer;

[0100] (5) The PbZr layer obtained in step (4) contains 3 layers 0.6 Ti 0.4 PbO colloid was dropped onto the thin film II containing the O3 component layer, and the film was deposited, dried, pyrolyzed, and annealed in air to crystallize, thus obtaining a thin film containing one PbO component layer.

[0101] (6) PbZr is dropped onto the thin film containing one layer of PbO obtained in step (5). 0.6 Ti 0.4 O3 colloid was coated, dried, pyrolyzed, and annealed in air to crystallize. This process was repeated 5 times to obtain a PbZr layer containing 6 layers. 0.6 Ti 0.4 Thin film III with O3 component layer is obtained, which is a PZT-based composite film with a wide temperature range negative electrocaloric effect.

[0102] The steps (1)-(6) mentioned above, namely coating, drying, pyrolysis, and annealing in air atmosphere for crystallization, are as follows: spin coating is performed at 4000 rpm for 30 s using a spin coater, drying at 300 ℃ for 6 min to remove moisture, pyrolysis at 500 ℃ for 6 min to remove organic matter, and finally annealing in air atmosphere at 750 ℃ ​​for 6 min for crystallization.

[0103] The preparation method of the above TiO2 colloid is as follows:

[0104] (1) Mix glacial acetic acid and CH3COCH2COCH3 at a volume ratio of 1:4 to obtain a mixed solution;

[0105] (2) At room temperature, Ti(OC4H9)4 raw material was dissolved in the mixture, stirred for 0.8 h, and aged for 24 h to obtain TiO2 colloid with a concentration of 0.2 mol / L.

[0106] The above PbZr 0.6 Ti 0.4 The preparation method of O3 colloid is as follows:

[0107] (1) Using Pb(CH3COO)2·3H2O, Ti(OC4H9)4 and Zr(OC3H7)4 as raw materials, according to PbZr 0.6 Ti 0.4 The chemical composition of O3 is determined by weighing the raw materials;

[0108] (2) Mix glacial acetic acid and CH3COCH2COCH3 at a volume ratio of 1:4 to obtain mixture I;

[0109] (3) Dissolve the raw material Pb(CH3COO)2·3H2O in glacial acetic acid at 130 °C at a concentration of 0.7 mol / L to obtain mixture II;

[0110] (4) At room temperature, the raw material Ti(OC4H9)4 was dissolved in mixed solution I at a concentration of 0.7 mol / L, and then the raw material Zr(OC3H7)4 was added to continue dissolving to obtain mixed solution III;

[0111] (5) Mix the obtained mixture II and mixture III completely, add mixture I for concentration correction, stir for 0.8 h, and let it age for 24 h to obtain PbZr with a concentration of 0.2 mol / L. 0.6 Ti 0.4 O3 colloid.

[0112] The above Hf 0.5 Zr 0.5 The preparation method of O2 colloid is as follows:

[0113] (1) Mix glacial acetic acid and CH3COCH2COCH3 at a volume ratio of 1:4 to obtain a mixed solution;

[0114] (2) According to Hf 0.5 Zr 0.5 The chemical composition of O2 is determined by weighing C8H. 20 HfO4 and Zr(OC3H7)4, and C8H 20 HfO4 and Zr(OC3H7)4 were dissolved in a mixed solution at room temperature, stirred for 0.8 h, and aged for 24 h to obtain HfO4 with a concentration of 0.2 mol / L. 0.5 Zr 0.5 O2 colloid.

[0115] The preparation method of the above PbO colloid is as follows:

[0116] (1) Mix glacial acetic acid and CH3COCH2COCH3 at a volume ratio of 1:4 to obtain a mixed solution;

[0117] (2) Dissolve the raw material Pb(CH3COO)2·3H2O in the mixed solution at 130℃, stir for 0.8 h, and let it age for 24 h to obtain PbO colloid with a concentration of 0.2 mol / L.

[0118] Comparative Example 1

[0119] Unlike Example 1, the PZT-based composite film consists of two layers of Hf. 0.5 Zr 0.5 O2 component layer, 3-layer PbZr 0.3 Ti 0.7 O3 component layer, 1 TiO2 component layer, 3 PbZr layer 0.3 Ti 0.7 O3 component layer, 1 layer of PbO component layer and 6 layers of PbZr 0.3 Ti 0.7 The O3 components were obtained by layering and stacking, and the rest was the same as in Example 1.

[0120] Comparative Example 2

[0121] Unlike Example 1, the PZT-based composite film consists of a TiO2 component layer and 12 PbZr components. 0.3 Ti 0.7 O3 component layer, 1 layer of PbO component layer and 2 layers of Hf 0.5 Zr 0.5 The O2 components were obtained by layering and stacking, and the rest was the same as in Example 1.

[0122] Comparative Example 3

[0123] Unlike Example 1, the PZT-based composite film consists of one TiO2 component layer and six PbZr layers. 0.3 Ti 0.7 O3 component layer, 2-layer Hf 0.5 Zr 0.5 O2 component layer, 3-layer PbZr 0.3 Ti 0.7 O3 component layer, 1 layer of PbO component layer and 3 layers of PbZr 0.3 Ti 0.7 The O3 components were obtained by layering and stacking, and the rest was the same as in Example 1.

[0124] Comparative Example 4

[0125] Unlike Example 1, the PZT-based composite film consists of one TiO2 component layer and three PbZr components. 0.3 Ti 0.7 O3 component layer, 1 layer of Hf0.5 Zr 0.5 O2 component layer, 3-layer PbZr 0.3 Ti 0.7 O3 component layer, 1 layer of PbO component layer and 6 layers of PbZr 0.3 Ti 0.7 The O3 components were obtained by layering and stacking, and the rest was the same as in Example 1.

[0126] Comparative Example 1 uses the TiO2 layer and Hf layer from Example 1. 0.5 Zr 0.5 The order of the O2 thin films was interchanged in Comparative Example 2, where the two Hf layers from Example 1 were replaced. 0.5 Zr 0.5 O2 and 6 layers of PbZr 0.3 Ti 0.7 The order of the O3 thin films was interchanged; in Comparative Example 3, the three PbZr samples from Example 1 were compared. 0.3 Ti 0.7 The number of O3 film layers was adjusted from 3, 3, 6 to 6, 3, 3. Comparative Example 3 changed the Hf in Example 1... 0.5 Zr 0.5 The O2 film was changed from two layers to one layer.

[0127] In Comparative Example 1, Hf 0.5 Zr 0.5 With the O2 film placed at the bottom layer, the loss of the TiO2 film to optimize orientation growth and improve crystallinity leads to an increase in defects at the bottom layer interface, resulting in a deterioration in electrocaloric performance and a decrease in the values ​​of adiabatic temperature change ΔT and adiabatic entropy change ΔS.

[0128] In Comparative Example 2, 2 layers of Hf 0.5 Zr 0.5 O2 and 6 layers of PbZr 0.3 Ti 0.7 The interchange of the O3 film order resulted in the formation of 12 layers of PbZr. 0.3 Ti 0.7 Although continuous PZT films can concentrate the polarization response and improve the peak positive electrocaloric effect, the overall operating temperature range of the film is narrowed due to the loss of interfacial coupling and stress modulation, and the negative electrocaloric effect is also weakened.

[0129] In Comparative Example 3, the lower PZT film layer of the adjusted film has a higher proportion and becomes dominant. Although starting from a thicker homogeneous PZT region is more advantageous in obtaining the peak caloric effect, and the values ​​of adiabatic temperature change ΔT and adiabatic entropy change ΔS increase slightly, it also weakens Hf to some extent. 0.5 Zr 0.5 The relaxation broadening effect of the O2 component layer results in a narrower operating temperature range for the thin film.

[0130] In Comparative Example 4, Hf 0.5 Zr 0.5 The reduction in the number of O2 film layers weakens the control mechanism of the composite film, resulting in a slight decrease in the overall performance of the film. The values ​​of the adiabatic temperature change ΔT and adiabatic entropy change ΔS of the negative electrocaloric effect become smaller, and the operating temperature range of the negative electrocaloric effect narrows.

[0131] Therefore, in summary, Example 1, compared to Comparative Examples 1-4, is better able to achieve a wide-temperature-range negative electrocaloric effect while maintaining high adiabatic temperature change ΔT and adiabatic entropy change ΔS in the PZT-based composite film.

[0132] The above description is a detailed description of the preferred embodiments of the present invention. However, the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modifications made under the technical spirit of the present invention should fall within the patent scope covered by the present invention.

Claims

1. A PZT-based composite thin film exhibiting a wide-temperature-range negative electrocaloric effect, characterized in that: The components consist of TiO2 layers and Hf, respectively. 0.5 Zr 0.5 O2 component layer, PbO component layer and PbZr x Ti 1-x The O3 component layers are obtained by alternating layers, where x represents the mole fraction, 0.20 ≤ x ≤ 0.60, and each component layer is either a single-layer thin sheet or composed of multiple layers of thin sheets.

2. The PZT-based composite thin film with a wide temperature range negative electrocaloric effect as described in claim 1, characterized in that: It consists of a TiO2 layer and three PbZr layers sequentially. x Ti 1-x O3 component layer, 2-layer Hf 0.5 Zr 0.5 O2 component layer, 3-layer PbZr x Ti 1-x O3 component layer, 1 layer of PbO component layer and 6 layers of PbZr x Ti 1-x The O3 components were obtained by layering and stacking.

3. The PZT-based composite thin film with a wide temperature range negative electrocaloric effect as described in claim 2, characterized in that: The thickness of each layer is 10-50 nm.

4. The method for preparing the PZT-based composite thin film with a wide temperature range negative electrocaloric effect as described in any one of claims 1-3, characterized in that, Includes the following steps: (1) Drop TiO2 colloid onto the substrate, perform film deposition, dry, pyrolyze, anneal in air atmosphere to crystallize, and repeat this step 0-5 times to obtain a thin film containing TiO2 component layer; (2) PbZr is dropped onto the film containing TiO2 component layer obtained in step (1). x Ti 1-x O3 colloid is coated, dried, pyrolyzed, and annealed in air to crystallize. This step is repeated 0-5 times to obtain a PbZr-containing product. x Ti 1-x Thin film I of O3 component layer; (3) The PbZr-containing sample obtained in step (2) x Ti 1-x Hf was dropped onto the thin film I of the O3 component layer. 0.5 Zr 0.5 O2 colloid is coated, dried, pyrolyzed, and annealed in air to crystallize. This step is repeated 0-5 times to obtain a product containing Hf. 0.5 Zr 0.5 Thin film of O2 component layer; (4) The Hf-containing sample obtained in step (3) 0.5 Zr 0.5 PbZr was dropped onto the O2 component layer film. x Ti 1-x O3 colloid is coated, dried, pyrolyzed, and annealed in air to crystallize. This step is repeated 0-5 times to obtain a PbZr-containing product. x Ti 1-x Thin film II of O3 component layer; (5) The PbZr-containing sample obtained in step (4) x Ti 1-x PbO colloid was dropped onto the thin film II containing the O3 component layer, and the film was deposited, dried, pyrolyzed, and annealed in air to crystallize. This step was repeated 0-5 times to obtain a thin film containing the PbO component layer. (6) PbZr is dropped onto the thin film containing the PbO component layer obtained in step (5). x Ti 1-x O3 colloid is coated, dried, pyrolyzed, and annealed in air to crystallize. This step is repeated 0-5 times to obtain a PbZr-containing product. x Ti 1-x Thin film III with O3 component layer is obtained, which is a PZT-based composite film with a wide temperature range negative electrocaloric effect.

5. The method for preparing the PZT-based composite thin film with a wide temperature range negative electrocaloric effect as described in claim 4, characterized in that: The steps (1)-(6) mentioned above, namely coating, drying, pyrolysis, and annealing in air atmosphere for crystallization, are as follows: spin coating is performed using a spin coater at a speed of 2000-6000 rpm for 25-35 s, drying is performed at 200-400 ℃ for 2-10 min to remove moisture, pyrolysis is performed at 400-600 ℃ for 2-10 min to remove organic matter, and finally annealing is performed at 700-800 ℃ in air atmosphere for 2-10 min for crystallization.

6. The method for preparing the PZT-based composite thin film with a wide temperature range negative electrocaloric effect as described in claim 4, characterized in that: The method for preparing the TiO2 colloid is as follows: (1) Mix glacial acetic acid and CH3COCH2COCH3 at a volume ratio of 1:2-4 to obtain a mixed solution; (2) At room temperature, Ti(OC4H9)4 raw material is dissolved in the mixture, stirred for 0.5-1 h, and aged for 12-36 h to obtain TiO2 colloid with a concentration of 0.2-0.3 mol / L.

7. The method for preparing the PZT-based composite thin film with a wide temperature range negative electrocaloric effect as described in claim 4, characterized in that: The PbZr x Ti 1-x The preparation method of O3 colloid is as follows: (1) Using Pb(CH3COO)2·3H2O, Ti(OC4H9)4 and Zr(OC3H7)4 as raw materials, according to PbZr x Ti 1-x The chemical composition of O3 is determined by weighing the raw materials, where 0.2 ≤ x ≤ 0.60; (2) Mix glacial acetic acid and CH3COCH2COCH3 at a volume ratio of 1:2-4 to obtain mixture I; (3) Dissolve the raw material Pb(CH3COO)2·3H2O in glacial acetic acid at 100-150 °C at a concentration of 0.7-0.9 mol / L to obtain mixture II; (4) At room temperature, the raw material Ti(OC4H9)4 was dissolved in mixed solution I at a concentration of 0.7-0.9 mol / L, and then the raw material Zr(OC3H7)4 was added to continue dissolving to obtain mixed solution III; (5) Mix the obtained mixture II and mixture III completely, add mixture I for concentration correction, stir for 0.5-1 h, and let it age for 12-36 h to obtain PbZr with a concentration of 0.2-0.3 mol / L. x Ti 1-x O3 colloid.

8. The method for preparing the PZT-based composite thin film with a wide temperature range negative electrocaloric effect as described in claim 4, characterized in that: The Hf 0.5 Zr 0.5 The preparation method of O2 colloid is as follows: (1) Mix glacial acetic acid and CH3COCH2COCH3 at a volume ratio of 1:2-4 to obtain a mixed solution; (2) According to Hf 0.5 Zr 0.5 The chemical composition of O2 is determined by weighing C8H. 20 HfO4 and Zr(OC3H7)4, and C8H 20 HfO4 and Zr(OC3H7)4 were dissolved in a mixed solution at room temperature, stirred for 0.5–1 h, and aged for 12–36 h to obtain HfO4 with a concentration of 0.2–0.3 mol / L. 0.5 Zr 0.5 O2 colloid.

9. The method for preparing the PZT-based composite thin film with a wide temperature range negative electrocaloric effect as described in claim 4, characterized in that: The method for preparing the PbO colloid is as follows: (1) Mix glacial acetic acid and CH3COCH2COCH3 at a volume ratio of 1:2-4 to obtain a mixed solution; (2) Dissolve the raw material Pb(CH3COO)2·3H2O in the mixed solution at 100-150 °C, stir for 0.5-1 h, and let it age for 12-36 h to obtain PbO colloid with a concentration of 0.2-0.3 mol / L.

10. The method for preparing the PZT-based composite thin film with a wide temperature range negative electrocaloric effect as described in claim 4, characterized in that: Step (1) is repeated 0 times to obtain a thin film containing one TiO2 component layer; Step (2) is repeated 2 times to obtain a thin film containing three PbZr components. x Ti 1-x O3 component layer thin film I; Step (3) is repeated once more to obtain a thin film containing 2 Hf layers. 0.5 Zr 0.5 The O2 component layer thin film; step (4) is repeated twice to obtain a thin film containing three layers of PbZr. x Ti 1-x Thin film II with O3 component layer; Step (5) is repeated 0 times to obtain a thin film with 1 PbO component layer; Step (6) is repeated 5 times to obtain a thin film with 6 PbZr components. x Ti 1-x Thin film III with O3 component layer.

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