CN106642798B

CN106642798B - Refrigeration system

Info

Publication number: CN106642798B
Application number: CN201611028720.4A
Authority: CN
Inventors: 黄斯昭; 陈朗
Original assignee: Southwest University of Science and Technology
Current assignee: Southwest University of Science and Technology
Priority date: 2016-11-18
Filing date: 2016-11-18
Publication date: 2021-11-23
Anticipated expiration: 2036-11-18
Also published as: CN106642798A

Abstract

The present invention relates to a refrigeration system. The refrigeration system includes a housing, a refrigeration element, and a heat transfer member. The shell is provided with a vacuum sealed accommodating space; the refrigerating element is accommodated in the accommodating space and comprises at least two stacked electrodes and a refrigerating unit, the polarities of the two adjacent electrodes are opposite, the refrigerating unit is stacked between every two adjacent electrodes, the refrigerating unit comprises a piezoelectric layer and a ferroelectric layer stacked on the piezoelectric layer, the phase transition temperature of the material of the piezoelectric layer is-10-30 ℃, and the phase transition temperature of the material of the ferroelectric layer is-10-30 ℃. The refrigerating system has a good cooling effect.

Description

Refrigeration system

Technical Field

The present invention relates to a refrigeration system.

Background

Different from the traditional evaporation-compression cooling mechanism depending on the specific heat and phase change of a coolant in the past, the electric card cooling system is a cooling mechanism which achieves the refrigeration effect by applying a certain electric field and utilizing the change of the entropy of the material by depending on the polarization characteristic of the material, so that compared with the traditional cooling mechanism, the electric card cooling system is not only efficient, small in size, compact in structure, free of lead and environment-friendly and pollution-free, can be applied to the field of microelectronics, and has very important application prospect.

The existing electric card refrigeration system generally adopts ferroelectrics to realize refrigeration, but the adiabatic temperature of the ferroelectrics is lower, so that the existing electric card refrigeration system has the problem of poor refrigeration effect.

Disclosure of Invention

Therefore, a refrigeration system with better cooling effect is needed.

A refrigeration system comprising:

the shell is provided with a vacuum sealed accommodating space;

the refrigerating element is accommodated in the accommodating space and comprises at least two stacked electrodes and a refrigerating unit, the polarities of the two adjacent electrodes are opposite, the refrigerating unit is stacked between every two adjacent electrodes, the refrigerating unit comprises a piezoelectric layer and a ferroelectric layer stacked on the piezoelectric layer, the phase transition temperature of the material of the piezoelectric layer is-10-30 ℃, and the phase transition temperature of the material of the ferroelectric layer is-10-30 ℃;

and the heat conducting piece is partially accommodated in the shell and is fixedly connected with the refrigerating element, and the heat conducting piece is used for conducting the heat of the refrigerating element to the outside.

In one embodiment, the piezoelectric layer is made of a material selected from the group consisting of lead titanate, lead zirconate titanate, barium titanate, bismuth ferrite, and lead magnesium niobate titanate.

In one embodiment, the material of the ferroelectric layer is selected from one of barium titanate, lead zirconate titanate, lead titanate, bismuth ferrite, potassium hydrogen phosphate, lead hydrogen phosphate, and lead phosphate.

In one embodiment, the number of the electrodes is two, the number of the refrigeration units is one, and the thickness of the refrigeration units is not more than 200 nanometers.

In one embodiment, the number of the electrodes is two, the number of the refrigeration units is one, and the thickness of the refrigeration units is 10-200 nanometers.

In one embodiment, the number of the electrodes is two, a plurality of the refrigeration units which are sequentially stacked are stacked between the two electrodes, and the sum of the thicknesses of the refrigeration units is not more than 200 nanometers.

In one embodiment, the number of the electrodes is at least three, and the sum of the thicknesses of all the refrigeration units does not exceed 200 nanometers.

In one embodiment, the heat dissipation device further comprises a heat dissipation member disposed outside the housing, and the heat dissipation member is fixedly connected to the heat conduction member.

In one embodiment, a reflective film is disposed on an inner surface of the housing.

In one embodiment, the material of the electrode is selected from one of copper, aluminum, indium, platinum, silver, gold, and a non-magnetic alloy.

Because the prior electric card refrigeration system is characterized in that the insulation temperature contributed by entropy change caused by polarization state change of ferroelectric effect near room temperature is lower only by the ferroelectric under an external electric field, so that the cooling temperature is lower, and the refrigeration effect is poorer, the refrigeration system forms a refrigeration unit by laminating a ferroelectric layer of a material with the phase transition temperature of-10 ℃ -30 ℃ and a piezoelectric layer of a material with the phase transition temperature of-10 ℃ -30 ℃, and the refrigeration unit is arranged between an anode and a cathode, wherein d33 (the piezoelectric deformation quantity along 33 direction in a piezoelectric material) can deform when the change is the maximum, the ferroelectric layer can deform, and lattice dimension change can be generated on the ferroelectric layer laminated on the piezoelectric layer to introduce mechanical strain to the ferroelectric layer, which is equivalent to introducing a second action field to the ferroelectric layer, namely the stress field, the entropy change of the ferroelectric layer is increased through the regulation and control of the stress field so as to increase the heat insulation temperature of the ferroelectric layer and increase the cooling temperature of the refrigeration system, thereby leading the refrigeration system to have better cooling effect.

Drawings

FIG. 1 is a schematic diagram of a refrigeration system according to one embodiment;

FIG. 2 is a schematic diagram of the refrigeration components of the refrigeration system of FIG. 1;

FIG. 3 is a schematic diagram of the construction of the refrigeration components of another embodiment of the refrigeration system;

fig. 4 is a schematic configuration diagram of a refrigeration unit of a refrigeration system according to another embodiment;

fig. 5 is a flow chart of a method of making a refrigeration component according to an embodiment.

Detailed Description

To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

As shown in fig. 1, the refrigeration system 100 of an embodiment is an all-solid-state electric card refrigeration system, and the refrigeration system 100 includes a housing 110, a power source 120, a refrigeration element 130, and a heat conducting member 140.

The housing 110 has a vacuum-tight receiving space 112.

Specifically, a reflective film (not shown) is provided on an inner surface of the case 110 to prevent heat radiation. Specifically, the reflective film is an aluminum film or a tin film.

The power source 120 is the power supply for the entire refrigeration system 100.

The cooling element 130 is accommodated in the accommodating space 112. The refrigeration component 130 is a core component of the overall refrigeration system 100.

Referring also to fig. 2, in the illustrated embodiment, the cooling element 130 includes two stacked electrodes 132 and a cooling unit 134.

The two electrodes 132 are of opposite polarity. I.e., one of the two electrodes 132 is a positive electrode and the other is a negative electrode. Wherein, the two electrodes 132 of the refrigeration element 130 are electrically connected with the positive electrode and the negative electrode of the power source 120 respectively.

Wherein, the material of the electrode 132 is selected from one of copper, aluminum, indium, platinum, silver, gold and non-magnetic alloy; the non-magnetic alloy is steel, magnesium aluminum alloy, platinum tin alloy, etc.

Wherein the thickness of the electrode 132 is 20 nm to 120 nm. The thickness and material of the two electrodes 132 may be the same or different, as long as the ohmic resistance of the conductive contact is small enough.

The refrigeration unit 134 is stacked between the two electrodes 132. The refrigeration unit 134 includes a piezoelectric layer 1342 and a ferroelectric layer 1344 stacked on the piezoelectric layer 1342. That is, one of the two electrodes 132 is stacked on a surface of the piezoelectric layer 1342 remote from the ferroelectric layer 1344, and the other is stacked on a surface of the ferroelectric layer 1344 remote from the piezoelectric layer 1342. The following formula is known:

wherein, in the above formula,. DELTA.T_mIs the amount of adiabatic temperature change,

and

which are polynomials of three partial equations that represent the three effects of the refrigeration unit 134 in a field, respectively the magnetic card effect, the flip card effect, and the electric card effect. The formula can find that the multi-field coupling is a positive superposition effect and has an effect of improving the adiabatic temperature variation of the whole material.

The phase transition temperature of the material of the piezoelectric layer 1342 is-10 ℃ to 30 ℃. Specifically, the material of the piezoelectric layer 1342 is one selected from lead titanate, lead zirconate titanate, barium titanate, bismuth ferrite, and lead magnesium niobate titanate. Wherein the lead magnesium niobate titanate has a structural formula of (PbMg)_0.33Nb_0.67O₃)_1-x:(PbTiO₃)_xX is 0.1-0.5, abbreviated as PMNPT; the structural formula of the lead zirconate titanate is Pb_yZr_1-yTiO₃Wherein y is more than 0 and less than 1.

Specifically, the material of the piezoelectric layer 1342 is preferably lead magnesium niobate titanate, because such material deforms in an electric field to induce a strain in the ferroelectric material epitaxially grown on the surface thereof in addition to the electric field.

The phase of the material of the ferroelectric layer 1344 is-10 to 30 ℃. The phase transition temperature of the material of the ferroelectric layer 1344 and the phase transition temperature of the material of the piezoelectric layer 1342 are both-10 ℃ to 30 ℃, firstly, the temperature region conforms to the market application range, and both cooling and heating are available; secondly, due to market guidance, when the material is selected, polarization change is most obvious only when the temperature region has phase change, and each partial polynomial has the largest contribution at the time, so that the variation of the adiabatic temperature is the largest, and the variation of the refrigerating and heating temperature is most obvious.

Specifically, the material of the ferroelectric layer 1344 is one selected from Barium Titanate (BTO), lead zirconate titanate (PZT), lead titanate, bismuth ferrite, potassium hydrogen phosphate, lead hydrogen phosphate, and lead phosphate.

In order to obtain a better adiabatic temperature, the combination of the piezoelectric layer 1342 and the ferroelectric layer 1344 may be selected as the following combination: the piezoelectric layer 1342 is made of lead zirconate titanate (PZT), and the ferroelectric layer 1344 is made of barium titanate; alternatively, the piezoelectric layer 1342 is made of lead zirconate titanate (PZT), and the ferroelectric layer 1344 is made of Bismuth Ferrite (BFO); alternatively, the material of the piezoelectric layer 1342 is lead magnesium niobate titanate, and the material of the ferroelectric layer 1344 is lead zirconate titanate (PZT); alternatively, the piezoelectric layer 1342 is made of lead magnesium niobate titanate, and the ferroelectric layer 1344 is made of Bismuth Ferrite (BFO); alternatively, the material of the ferroelectric layer 1344 is barium titanate, and the material of the piezoelectric layer 1342 is lead magnesium niobate titanate. The piezoelectric layer 1342 and the ferroelectric layer 1344 of the refrigeration unit 134 are formed by combining the above materials, so that the refrigeration unit 134 has a relatively high heat insulation temperature. However, the material of the ferroelectric layer 1344 is barium titanate, and the piezoelectric layer 1342 formed by matching with lead magnesium niobate titanate can make the refrigeration unit 134 have a higher heat insulation temperature, a better cooling effect, and a better cooling effect for the refrigeration system 100, so in this embodiment, preferably, the material of the ferroelectric layer 1344 is barium titanate, and the material of the piezoelectric layer 1342 is lead magnesium niobate titanate.

Wherein the thickness of the refrigeration unit 134 does not exceed 200 nanometers. That is, the thicknesses of ferroelectric layer 1344 and piezoelectric layer 1342 are both less than 200 nm, and piezoelectric layer 1342 and ferroelectric layer 1344 are both thin films. That is, the thickness of the refrigeration unit 134 is thin and is a film, and compared with a block-shaped refrigeration unit, the film-shaped refrigeration unit 134 has higher entropy change, thereby being beneficial to obtaining a larger heat insulation temperature change range. For a refrigeration unit 134 with multiple effects, the larger the applied electric field, the larger the entropy change and the larger the adiabatic temperature change, and the film refrigeration unit 134 has a great advantage in anti-breakdown performance compared with the block refrigeration unit.

Further, the thickness of the refrigeration unit 134 is 10 nm to 200 nm.

The heat conduction member 140 is partially received in the housing 110 and is fixedly connected to the refrigeration component 130, and the heat conduction member 140 is used for conducting heat from the refrigeration component 130 to the outside.

In the present embodiment, the material of the heat conducting member 140 is copper. It is understood that the material of the thermal conductive member 140 is not limited to copper, and any material with better thermal conductivity can be used.

Further, the refrigeration system 100 further includes a heat sink 150 disposed outside the outer shell 110, and the heat sink 150 is fixedly connected to the heat conduction member 140. It is understood that the heat sink 150 may be a heat sink or the like; alternatively, the heat sink 150 may be omitted, and in this case, the heat conduction member 140 directly conducts the hot air to the air.

Because the existing electric card refrigeration system is characterized in that the insulation temperature contributed by entropy change caused by polarization state change of ferroelectric effect near room temperature is low only by the ferroelectric under an external electric field, so that the cooling temperature is low, and the refrigeration effect is poor, the refrigeration system 100 is used by laminating the ferroelectric layer 1344 of a material with a phase transition temperature of-10 ℃ to 30 ℃ with the piezoelectric layer 1342 of a material with a phase transition temperature of-10 ℃ to 30 ℃, wherein the piezoelectric layer 1342 can be significantly deformed along with the change of the electric field under the action of the electric field, when d33 (which refers to the piezoelectric deformation amount in the direction 33 in the piezoelectric material) is changed maximally, the ferroelectric layer 1344 is deformed, and lattice dimension change is generated on the ferroelectric layer 1344 laminated on the piezoelectric layer 1342 to introduce mechanical strain to the ferroelectric layer 1344, which is equivalent to introducing a second electric field to the ferroelectric layer 1344, that is, the stress field is controlled to increase the entropy change of the ferroelectric layer 1344, so as to further increase the adiabatic temperature of the ferroelectric layer 1344, and the larger the adiabatic temperature is, the larger the cooling temperature is, the better the cooling effect is, so that the refrigeration system 100 has a better cooling effect; meanwhile, the refrigeration effect of the refrigeration system 100 can be further ensured by installing the refrigeration element 130 in the vacuum-sealed accommodating space 112 and conducting the heat of the refrigeration element 130 to the outside through the heat conducting member 140.

As shown in fig. 3, the refrigeration system of the other embodiment has substantially the same configuration as the refrigeration system 100, and differs therefrom only in that the refrigeration system of the present embodiment has a different configuration of the refrigeration element 200.

A plurality of refrigeration units 220 stacked in sequence are stacked between two electrodes 210 of the refrigeration element 200 of the refrigeration system of the present embodiment, that is, a plurality of piezoelectric layers 222 and a plurality of ferroelectric layers 224 are alternately disposed between two electrodes 210 of the present embodiment, wherein one piezoelectric layer 222 and one ferroelectric layer 224 stacked form one refrigeration unit 220. The piezoelectric layers 222 of the plurality of refrigeration units 220 may be made of the same material or different materials; the materials of the ferroelectric layers 224 may be the same or different.

At this time, the sum of the thicknesses of the plurality of refrigeration units 220 does not exceed 200 nm.

Further, the sum of the thicknesses of the plurality of refrigeration units 220 is 10 nm to 200 nm. For example, in the illustrated embodiment, there are two refrigeration units 220, and the sum of the thicknesses of the two refrigeration units 220 is 10 nm to 200 nm. It is understood that the number of the refrigeration units 220 is not limited to two, but may be three, four or more.

Since the refrigeration system of the present embodiment has a structure similar to that of the refrigeration system 100, the refrigeration system of the present embodiment also has an effect similar to that of the refrigeration system 100. And the structure of the refrigeration system of the present embodiment in which the repeated refrigeration units 220 are provided can reduce the leakage points, improve the intensity of the voltage allowed to be applied, and thus improve the adiabatic temperature variation amount.

As shown in fig. 4, the refrigeration system of the present embodiment has substantially the same configuration as the refrigeration system 100, and differs therefrom only in the configuration of the refrigeration element 300 of the refrigeration system of the present embodiment.

The refrigeration element 300 of the present embodiment includes at least three stacked electrodes 310 and a refrigeration unit 320.

Wherein the polarities of the adjacent two electrodes 310 are opposite. That is, one of the two adjacent electrodes 310 is a positive electrode, and the other is a negative electrode.

The material of the electrode 310 is the same as that of the electrode 310 according to an embodiment.

Wherein, a refrigeration unit 320 is arranged between every two adjacent electrodes 310, that is, the refrigeration unit 320 and the plurality of electrodes 310 are alternately arranged. It is understood that each two adjacent electrodes 310 are not limited to one refrigeration unit 320, and a plurality of stacked refrigeration units 320 may be disposed between two adjacent electrodes 310, similar to the refrigeration element 200.

The refrigeration unit 320 has the same structure as the refrigeration unit 320 according to the embodiment, and includes a piezoelectric layer 322 and a ferroelectric layer 324 laminated on the piezoelectric layer 322.

Wherein, in the refrigerating element 300, the sum of the thicknesses of all the refrigerating units 320 does not exceed 200 nm.

Further, the sum of the thicknesses of all the refrigeration units 320 is 10 nm to 200 nm.

Specifically, the electrode 310 having a positive polarity is electrically connected, and the electrode 310 having a negative polarity is electrically connected.

More specifically, the refrigeration element 300 further includes a first conductive member 330 and a second conductive member 340, the first conductive member 330 is electrically connected to the electrode 310 with the positive polarity, and the second conductive member 340 is electrically connected to the electrode 310 with the negative polarity. That is, the electrode 310 with the positive polarity is electrically connected to the first conductive member 330; the electrode 310 with the negative polarity is electrically connected to the second conductive member 340.

Further, the first conductive member 330 and the second conductive member 340 are respectively disposed at opposite sides of the stack of the plurality of electrodes 310 and the refrigeration unit 320.

The first conductive member 330 and the second conductive member 340 may be formed by respectively coating or evaporating conductive materials on opposite sides of the stacked member. The conductive material coated can be silver paste, etc.; the evaporated conductive material may be, for example, aluminum, zinc, copper, or the like. More specifically, the first conductive member 330 and the second conductive member 340 are made of silver.

Specifically, in the illustrated embodiment, there are four electrodes 310, three refrigeration units 320, and from bottom to top, the polarity of the first electrode 310 is opposite to that of the second electrode 310, the polarities of the first electrode 310 and the third electrode 310 are the same, the polarities of the second electrode 310 and the fourth electrode 310 are the same, the first electrode 310 and the third electrode 310 are electrically connected through a first conductive member 330, and the second electrode 310 and the fourth electrode 310 are electrically connected through a second conductive member 340. It is understood that in other embodiments, the number of the electrodes 310 is not limited to four, the number of the refrigeration units 320 is not limited to three, and the number of the electrodes 310 and the number of the refrigeration units 320 may be adjusted as needed as long as the refrigeration units 320 are disposed between two adjacent electrodes 310; the space between two adjacent electrodes 310 is not limited to one refrigeration unit 320, and more than two refrigeration units 320 may be disposed between two adjacent electrodes 310.

Since the refrigeration system 300 of the present embodiment also uses a ferroelectric layer 324 material of a material having a phase transition temperature of-10 to 30 ℃ and a piezoelectric layer 322 of a material having a phase transition temperature of-10 to 30 ℃ stacked as the refrigeration unit 320, the refrigeration system of the present embodiment also has similar effects to the refrigeration system 100.

And the refrigeration system with the structure forms the refrigeration unit 320 between every two electrodes 310, so that the process is simpler in the manufacturing aspect of the structure compared with the process for forming the refrigeration unit on the refrigeration unit, and the cost is reduced.

As shown in fig. 5, a method for manufacturing a refrigeration element according to an embodiment may be used for manufacturing a refrigeration element of the refrigeration system, where the method for manufacturing a refrigeration element includes the following steps:

step S410: a piezoelectric layer is formed on the ferroelectric layer to obtain a refrigeration unit.

Wherein the phase change of the material of the ferroelectric layer is-10 ℃ to 30 ℃. Specifically, the material of the ferroelectric layer is selected from Barium Titanate (BTO), lead zirconate titanate (PZT), lead titanate, bismuth ferrite, potassium hydrogen phosphate, lead hydrogen phosphate, and PbDPO₄One kind of (1).

Wherein the phase transition temperature of the material of the piezoelectric layer is-10 ℃ to 30 ℃. Specifically, the material of the piezoelectric layer is selected from one of lead titanate, lead zirconate titanate (PZT), barium titanate, Bismuth Ferrite (BFO) and lead magnesium niobate titanate, wherein the lead magnesium niobate titanate has a structural formula of (PbMg)_0.33Nb_0.67O₃)_1-x:(PbTiO₃)_xAnd x is 0.1-0.5, abbreviated as PMNPT.

Preferably, the material of the piezoelectric layer is lead zirconate titanate (PZT), and the material of the ferroelectric layer is barium titanate; or the piezoelectric layer is made of lead zirconate titanate (PZT) and the ferroelectric layer is made of Bismuth Ferrite (BFO); or the material of the piezoelectric layer is lead magnesium niobate titanate, and the material of the ferroelectric layer is lead zirconate titanate (PZT); or the piezoelectric layer is made of lead magnesium niobate titanate, and the ferroelectric layer is made of Bismuth Ferrite (BFO); the material of the ferroelectric layer is barium titanate, and the material of the piezoelectric layer is lead magnesium niobate titanate.

In this embodiment, a piezoelectric layer is formed on the ferroelectric layer by a laser pulse deposition (PLD). Specifically, the process parameters for forming the piezoelectric layer on the ferroelectric layer by using a laser pulse deposition method are as follows: the temperature is 600-850 ℃, and the laser energy density is 1.5mJ/cm²～2.5mJ/cm²And the oxygen pressure is 0.0013mbar to 1.3mbar, after the deposition is finished, the oxygen pressure is changed to 10mbar to 100mbar, and the static oxygen pressure in-situ annealing is carried out to reduce the temperature to the room temperature, namely a piezoelectric layer is formed on the ferroelectric layer, so that the refrigerating unit is obtained.

When the refrigeration element 200 is to be prepared, and a plurality of stacked refrigeration units are to be prepared, then after the first refrigeration unit is prepared according to the above method, the ferroelectric layer of the second refrigeration unit is deposited on the piezoelectric layer of the first refrigeration unit by using the laser pulse deposition method, and at this time, the process parameters for depositing the ferroelectric layer of the second refrigeration unit on the piezoelectric layer of the first refrigeration unit are as follows: the temperature is 600-850 ℃, and the laser energy density is 1.5mJ/cm²～2.5mJ/cm²The oxygen pressure is 0.0013mbar to 1.3mbar, after the deposition is finished, the oxygen pressure is changed to 10mbar to 100mbar, the static oxygen pressure in-situ annealing is carried out to reduce the temperature to the room temperature, and a ferroelectric layer of a second refrigeration unit is formed on the piezoelectric layer of the first refrigeration unit; forming a piezoelectric layer of a second refrigeration unit on the ferroelectric layer of the second refrigeration unit by adopting a laser pulse deposition method and a method for forming the piezoelectric layer on the ferroelectric layer of the first refrigeration unit according to the above method so as to obtain the second refrigeration unit; if a plurality of refrigeration units are needed, the preparation is repeated according to the method.

It is to be understood that the method of forming the piezoelectric layer on the ferroelectric layer is not limited to the laser pulse deposition method, and in other embodiments, the method may be an evaporation coating method, ion plating, chemical vapor deposition, solution film formation, or the like; the method of forming the ferroelectric layer of the other refrigeration unit on the piezoelectric layer of the previous refrigeration unit is not limited to the laser pulse deposition method, and in other embodiments, the method may be an evaporation coating method, ion plating, chemical vapor deposition, solution film deposition, or the like.

Step S420: one electrode is formed on each of a surface of the piezoelectric layer remote from the ferroelectric layer and a surface of the ferroelectric layer remote from the piezoelectric layer.

When the refrigeration element 130 is required to be prepared, an ion sputtering apparatus can be adopted to respectively evaporate electrodes on the surface of the piezoelectric layer far away from the ferroelectric layer and the surface of the ferroelectric layer far away from the piezoelectric layer; at the moment, the technological parameters of the evaporation plating electrode by adopting the ion sputtering instrument are as follows: in argon atmosphere, the ionization time is 60-120 seconds, and the evaporation is performed for 1-3 times.

When the prepared refrigeration element 200 is required, step S420 is: forming an electrode on the piezoelectric layer of the first refrigerating unit and the ferroelectric layer of the last refrigerating unit, respectively; in this case, the electrode may be manufactured by the same manufacturing method as the electrode of the refrigeration unit 130.

When the prepared refrigeration element 300 is required, step S420 is: a first baffle plate and a second baffle plate are respectively arranged at one end of the piezoelectric layer of the first refrigeration unit, which is far away from the ferroelectric layer, and one end of the ferroelectric layer, which is far away from the piezoelectric layer, so that the first baffle plate and the second baffle plate are respectively positioned at the two ends of the first refrigeration unit; then, respectively forming an electrode on one surface of the piezoelectric layer far away from the ferroelectric layer and one surface of the ferroelectric layer far away from the piezoelectric layer; forming a piezoelectric layer of a second refrigeration unit on the electrode close to the ferroelectric layer of the first refrigeration unit, forming another ferroelectric layer on the piezoelectric layer according to the method of step S410, arranging a third baffle on one end of the ferroelectric layer of the second refrigeration unit, which is far away from the piezoelectric layer, wherein the position of the third baffle corresponds to the position of the first baffle, and forming a third electrode on the surface of the ferroelectric layer, which is far away from the piezoelectric layer, and the position of the third electrode corresponds to the position of the electrode close to the piezoelectric layer of the first refrigeration unit;

and repeating the steps of preparing the second refrigeration unit and the third electrode to alternately arrange the subsequent refrigeration units and electrodes. As long as the two spaced electrodes correspond in position, all odd-numbered electrodes correspond in position from the electrode adjacent to the piezoelectric layer of the first refrigeration unit, and all even-numbered electrodes correspond in position from the electrode adjacent to the piezoelectric layer of the first refrigeration unit, i.e., all odd-numbered electrodes are flush with one side of the stack of electrodes and the plurality of refrigeration units at one end and all even-numbered electrodes are flush with the other side of the stack;

then, a first conductive member and a second conductive member are formed on both sides of the stacked member, and all odd-numbered electrodes are electrically connected to the first conductive member and all even-numbered electrodes are electrically connected to the second conductive member, as counted from the electrodes of the piezoelectric layer near the first refrigeration unit, to obtain the refrigeration element 300.

Wherein, the method for depositing the ferroelectric layer on the electrode is also a laser pulse deposition method; the technological parameters are as follows: the temperature is 600-850 ℃, and the laser energy density is 1.5mJ/cm²～2.5mJ/cm²And the oxygen pressure is 0.0013mbar to 1.3mbar, after the deposition is finished, the oxygen pressure is changed to 10mbar to 100mbar, and the static oxygen pressure in-situ annealing is carried out to reduce the temperature to the room temperature.

The method for forming the electrodes on the surface of the piezoelectric layer far away from the ferroelectric layer and the method for forming the electrodes on the surface of the ferroelectric layer far away from the piezoelectric layer are both methods for bombarding the metal target by pulse laser, and the technological parameters are as follows: at room temperature, vacuum degree of-5 mbar, energy of 1.5mJ/cm²～3mJ/cm²The number of pulses is 50 to 10000.

The first conductive piece and the second conductive piece are respectively formed on two sides of the laminated body by coating conductive materials or evaporating the conductive materials on two opposite sides of the laminated body. Wherein the coated conductive material is silver paste; the evaporated conductive material is aluminum, zinc, copper, etc.

Wherein, the material of the electrode is selected from one of copper, aluminum, indium, platinum, silver, gold and non-magnetic alloy. The non-magnetic alloy is steel, magnesium aluminum alloy, platinum tin alloy, etc.

Wherein the thickness of the electrode is 20-120 nm.

The preparation method of the refrigeration element is simple to operate and easy for industrial production. In the preparation method of the refrigerating element, the ferroelectric layer of the material with the phase transition temperature of-10-30 ℃ and the piezoelectric layer of the material with the phase transition temperature of-10-30 ℃ are laminated to be used as the refrigerating unit, and the refrigerating unit is applied to a refrigerating system, so that the prepared refrigerating system has a good refrigerating effect.

The following are specific examples:

example 1

The preparation process of the refrigeration system of the embodiment is as follows:

(1) forming a piezoelectric layer with a thickness of 50 nm on the ferroelectric layer with a thickness of 50 nm by laser pulse deposition at 700 deg.C and laser energy density of 2mJ/cm²After the deposition is finished, changing the oxygen pressure to 100mbar, and carrying out static oxygen pressure in-situ annealing to reduce the temperature to room temperature to obtain a refrigeration unit; wherein the ferroelectric layer is made of barium titanate, and the piezoelectric layer is made of lead magnesium niobate titanate [ (PbMg)_0.33Nb_0.67O₃)_1-x:(PbTiO₃)_x，x＝0.3]。

(2) Respectively evaporating an electrode on one side of the piezoelectric layer far away from the ferroelectric layer and one side of the ferroelectric layer far away from the piezoelectric layer by using an ion sputtering instrument to obtain a laminated body; the technological parameters of evaporating the electrodes on the side of the piezoelectric layer far away from the ferroelectric layer are as follows: in argon atmosphere, the ionization time is 90 seconds, the vapor deposition is carried out for 2 times, the thickness is 70 nanometers, and the material is silver; the technological parameters of evaporating the electrode on the side of the ferroelectric layer far away from the piezoelectric layer are as follows: argon atmosphere, ionization time 90 seconds, 2 times of evaporation, thickness of 70 nanometers, and silver as a material.

(3) The stacked member is fixedly installed in a housing having a vacuum-sealed accommodating space, the refrigeration unit of the stacked member is fixedly connected to a copper sheet partially accommodated in the housing, the other end of the copper sheet is connected to a radiator, and two electrodes are electrically connected to the positive electrode and the negative electrode of a power supply, respectively, so as to obtain the refrigeration system of the embodiment.

The two electrodes were energized and the adiabatic temperature of the refrigeration system of this example was tested using Differential Scanning Calorimetry (DSC) and is shown in table 1.

Example 2

(1) forming a piezoelectric layer with a thickness of 5 nm on the ferroelectric layer with a thickness of 5 nm by laser pulse deposition at 600 deg.C and laser energy density of 2.5mJ/cm²The oxygen pressure is 0.0013mbar, after the deposition is finished, the oxygen pressure is changed to 100mbar, and the static oxygen pressure in-situ annealing is carried out to reduce the temperature to the room temperature, so as to obtain a refrigeration unit; wherein the material of the ferroelectric layer is lead zirconate titanate (Pb)_0.5Zr_0.5TiO₃) (ii) a The piezoelectric layer is made of lead magnesium niobate titanate [ (PbMg)_0.33Nb_0.67O₃)_1-x:(PbTiO₃)_x，x＝0.1]。

(2) Respectively evaporating an electrode on one side of the piezoelectric layer far away from the ferroelectric layer and one side of the ferroelectric layer far away from the piezoelectric layer by using an ion sputtering instrument to obtain a laminated body; the technological parameters of evaporating the electrodes on the side of the piezoelectric layer far away from the ferroelectric layer are as follows: carrying out vapor deposition for 3 times in an argon atmosphere for 60 seconds, wherein the thickness of the vapor deposition is 20 nanometers, and the material is platinum; the technological parameters of evaporating the electrode on the side of the ferroelectric layer far away from the piezoelectric layer are as follows: argon atmosphere, ionization time 60 seconds, 3 times of evaporation, thickness of 20 nanometers, and platinum as material.

The adiabatic temperatures of the refrigeration system of this example were obtained using the same test methods as in example 1, and are shown in table 1.

Example 3

(1) forming a piezoelectric layer with a thickness of 100 nm on the ferroelectric layer with a thickness of 100 nm by laser pulse deposition at 700 deg.C and laser energy density of 2mJ/cm²After the deposition is finished, changing the oxygen pressure to 100mbar, and carrying out static oxygen pressure in-situ annealing to reduce the temperature to room temperature to obtain a refrigeration unit; wherein the ferroelectric layer is made of barium titanate, and the piezoelectric layer is made of lead magnesium niobate titanate [ (PbMg)_0.33Nb_0.67O₃)_1-x:(PbTiO₃)_x，x＝0.3]。

Example 4

(1) forming a first piezoelectric layer with a thickness of 30 nm on a first ferroelectric layer with a thickness of 20 nm by laser pulse deposition at a temperature of 30 nmAt 850 deg.C, the laser energy density is 1.5mJ/cm²After the deposition is finished, changing the oxygen pressure to 100mbar, and carrying out static oxygen pressure in-situ annealing to reduce the temperature to room temperature to obtain a first refrigeration unit; wherein the material of the first ferroelectric layer is lead titanate, and the material of the first piezoelectric layer is lead magnesium niobate titanate [ (PbMg)_0.33Nb_0.67O₃)_1-x:(PbTiO₃)_x，x＝0.5]。

(2) Forming a second ferroelectric layer with a thickness of 20 nm on the first piezoelectric layer by laser pulse deposition at 850 deg.C and laser energy density of 1.5mJ/cm²The oxygen pressure is 1.3mbar, after the deposition is finished, the oxygen pressure is 100mbar, and the static oxygen pressure in-situ annealing is carried out to reduce the temperature to the room temperature; wherein the material of the second ferroelectric layer is lead titanate.

(3) Forming a second piezoelectric layer with a thickness of 30 nm on the second ferroelectric layer by laser pulse deposition at 850 deg.C and laser energy density of 1.5mJ/cm²After the deposition is finished, the oxygen pressure is changed to 100mbar, and the static oxygen pressure in-situ annealing is carried out to reduce the temperature to the room temperature, so as to obtain a second refrigeration unit; wherein the material of the second piezoelectric layer is lead magnesium niobate titanate [ (PbMg)_0.33Nb_0.67O₃)_1-x:(PbTiO₃)_x，x＝0.5]。

(4) And respectively evaporating an electrode on one side of the first ferroelectric layer of the first refrigeration unit, which is far away from the first piezoelectric layer, and one electrode on one side of the second ferroelectric layer of the second refrigeration unit, which is far away from the second ferroelectric layer by adopting an ion sputtering instrument to obtain the laminated body. The technological parameters of evaporating and plating electrodes on one side of the first ferroelectric layer of the first refrigeration unit, which is far away from the first piezoelectric layer, are as follows: in argon atmosphere, the ionization time is 120 seconds, the evaporation is performed for 1 time, the thickness is 120 nanometers, and the material is aluminum; the technological parameters of the evaporated electrode on the side of the second piezoelectric layer of the second refrigeration unit, which is far away from the second ferroelectric layer, are as follows: argon atmosphere, ionization time 120 seconds, vapor deposition for 1 time, thickness of 120 nanometers, and material of aluminum.

(5) The stacked member is fixedly installed in a housing having a vacuum-sealed accommodating space, the refrigeration unit of the stacked member is fixedly connected to a copper sheet partially accommodated in the housing, the other end of the copper sheet is connected to a radiator, and two electrodes are electrically connected to the positive electrode and the negative electrode of a power supply, respectively, so as to obtain the refrigeration system of the embodiment.

Example 5

(1) forming a first piezoelectric layer with a thickness of 20 nm on a first ferroelectric layer with a thickness of 30 nm by laser pulse deposition at 750 deg.C and laser energy density of 1.8mJ/cm²After the deposition is finished, the oxygen pressure is changed to 10mbar, and the static oxygen pressure in-situ annealing is carried out to reduce the temperature to the room temperature, so as to obtain a first refrigeration unit; wherein the first ferroelectric layer is made of bismuth ferrite, and the first piezoelectric layer is made of lead magnesium niobate titanate [ (PbMg)_0.33Nb_0.67O₃)_1-x:(PbTiO₃)_x，x＝0.2]。

(2) Forming a second ferroelectric layer with a thickness of 40 nm on the first piezoelectric layer by laser pulse deposition at 750 deg.C and laser energy density of 1.8mJ/cm²The oxygen pressure is 0.1mbar, after the deposition is finished, the oxygen pressure is 10mbar, and the static oxygen pressure in-situ annealing is carried out to reduce the temperature to the room temperature; wherein, the material of the second ferroelectric layer is bismuth ferrite.

(3) Forming a second piezoelectric layer with a thickness of 30 nm on the second ferroelectric layer by laser pulse deposition at 750 deg.C and laser energy density of 1.8mJ/cm²After the deposition is finished, the oxygen pressure is changed to 10mbar, and the static oxygen pressure in-situ annealing is carried out to reduce the temperature to the room temperature, so as to obtain a second refrigeration unit; wherein the material of the second piezoelectric layer is lead magnesium niobate titanate [ (PbMg)_0.33Nb_0.67O₃)_1-x:(PbTiO₃)_x，x＝0.2]。

(4) At the second pressureForming a third ferroelectric layer with a thickness of 10 nm on the ferroelectric layer by laser pulse deposition at 750 deg.C and laser energy density of 1.8mJ/cm²The oxygen pressure is 0.1mbar, after the deposition is finished, the oxygen pressure is 10mbar, and the static oxygen pressure in-situ annealing is carried out to reduce the temperature to the room temperature; wherein the material of the third ferroelectric layer is potassium hydrogen phosphate.

(5) Forming a third piezoelectric layer with the thickness of 15 nanometers on the third ferroelectric layer by adopting a laser pulse deposition method, wherein the temperature is 750 ℃ and the laser energy density is 1.8mJ/cm in the laser pulse deposition process²After the deposition is finished, the oxygen pressure is changed to 10mbar, and the static oxygen pressure in-situ annealing is carried out to reduce the temperature to the room temperature, so as to obtain a third refrigeration unit; wherein the third piezoelectric layer is made of lead magnesium niobate titanate [ (PbMg)_0.33Nb_0.67O₃)_1-x:(PbTiO₃)_x，x＝0.2]。

(6) And respectively evaporating an electrode on one side of the first ferroelectric layer of the first refrigeration unit, which is far away from the first piezoelectric layer, and one electrode on one side of the third piezoelectric layer of the third refrigeration unit, which is far away from the third piezoelectric layer by adopting an ion sputtering instrument to obtain the laminated body. The technological parameters of evaporating and plating electrodes on one side of the first ferroelectric layer of the first refrigeration unit, which is far away from the first piezoelectric layer, are as follows: in argon atmosphere, the ionization time is 100 seconds, the vapor deposition is carried out for 2 times, the thickness is 70 nanometers, and the material is indium; the technological parameters of evaporating and plating electrodes on the side, far away from the third ferroelectric layer, of the third piezoelectric layer of the third refrigeration unit are as follows: argon atmosphere, ionization time 100 seconds, 2 times of evaporation, thickness of 70 nanometers, and indium as a material.

(7) The stacked member is fixedly installed in a housing having a vacuum-sealed accommodating space, the refrigeration unit of the stacked member is fixedly connected to a copper sheet partially accommodated in the housing, the other end of the copper sheet is connected to a radiator, and two electrodes are electrically connected to the positive electrode and the negative electrode of a power supply, respectively, so as to obtain the refrigeration system of the embodiment.

Example 6

(1) forming a first piezoelectric layer with a thickness of 5 nm on a first ferroelectric layer with a thickness of 10 nm by laser pulse deposition at 800 deg.C and laser energy density of 2.3mJ/cm²After the deposition is finished, changing the oxygen pressure to 50mbar, and carrying out static oxygen pressure in-situ annealing to reduce the temperature to room temperature to obtain a first refrigeration unit; wherein the material of the first ferroelectric layer is lead hydrogen phosphate, and the material of the first ferroelectric layer is lead magnesium niobate titanate [ (PbMg)_0.33Nb_0.67O₃)_1-x:(PbTiO₃)_x，x＝0.4]。

(2) Forming a second ferroelectric layer with a thickness of 20 nm on the first piezoelectric layer by laser pulse deposition at 800 deg.C and laser energy density of 2.3mJ/cm²The oxygen pressure is 1mbar, the oxygen pressure is changed to 50mbar after the deposition is finished, and the static oxygen pressure in-situ annealing is carried out to reduce the temperature to the room temperature; wherein, the material of the second ferroelectric layer is lead phosphate.

(3) Forming a second piezoelectric layer with a thickness of 30 nm on the second ferroelectric layer by laser pulse deposition at 800 deg.C and laser energy density of 2.3mJ/cm²After the deposition is finished, the oxygen pressure is changed to 50mbar, and the static oxygen pressure in-situ annealing is carried out to reduce the temperature to the room temperature, so as to obtain a second refrigeration unit; wherein the material of the second piezoelectric layer is lead titanate.

(4) Forming a third ferroelectric layer with a thickness of 20 nm on the second piezoelectric layer by laser pulse deposition at 800 deg.C and laser energy density of 2.3mJ/cm²The oxygen pressure is 1mbar, the oxygen pressure is changed to 50mbar after the deposition is finished, and the static oxygen pressure in-situ annealing is carried out to reduce the temperature to the room temperature; wherein the material of the third ferroelectric layer is barium titanate.

(5) Forming a third piezoelectric layer with the thickness of 30 nanometers on the third ferroelectric layer by adopting a laser pulse deposition method, wherein the temperature is 700 ℃ and the laser energy density is 1.9mJ/cm in the laser pulse deposition process²Oxygen, oxygenThe pressure is 0.08mbar, after the deposition is finished, the oxygen pressure is changed into 50mbar, and the static oxygen pressure in-situ annealing is carried out to reduce the temperature to the room temperature, so as to obtain a third refrigeration unit; wherein the material of the third piezoelectric layer is bismuth ferrite.

(6) Forming a fourth ferroelectric layer with a thickness of 25 nm on the third piezoelectric layer by laser pulse deposition at 600 deg.C and laser energy density of 1.6mJ/cm²The oxygen pressure is 1.2mbar, the oxygen pressure is changed into 50mbar after the deposition is finished, and the static oxygen pressure in-situ annealing is carried out to reduce the temperature to the room temperature; wherein the fourth ferroelectric layer is made of lead zirconate titanate (Pb)_0.1Zr_0.9TiO₃)。

(7) Forming a fourth piezoelectric layer with a thickness of 20 nm on the fourth ferroelectric layer by laser pulse deposition at 650 deg.C and laser energy density of 2mJ/cm²The oxygen pressure is 0.8mbar, the oxygen pressure is changed to 50mbar after the deposition is finished, and the static oxygen pressure in-situ annealing is carried out to reduce the temperature to the room temperature, so as to obtain a fourth refrigeration unit; wherein the fourth piezoelectric layer is made of lead magnesium niobate titanate [ (PbMg)_0.33Nb_0.67O₃)_1-x:(PbTiO₃)_x，x＝0.3]。

(8) And respectively evaporating a second electrode on one side of the first ferroelectric layer of the first refrigeration unit, which is far away from the first piezoelectric layer, and one side of the fourth piezoelectric layer of the fourth refrigeration unit, which is far away from the fourth ferroelectric layer by adopting an ion sputtering instrument to obtain the laminated body. The technological parameters of evaporating and plating electrodes on one side of the first ferroelectric layer of the first refrigeration unit, which is far away from the first piezoelectric layer, are as follows: in argon atmosphere, the ionization time is 80 seconds, the evaporation is carried out for 2 times, the thickness is 60 nanometers, and the material is copper; the process parameters of each evaporation electrode on the side of the fourth piezoelectric layer of the fourth refrigeration unit far away from the fourth ferroelectric layer are as follows: argon atmosphere, ionization time 80 seconds, 2 times of evaporation, thickness of 60 nanometers, and copper as a material.

(9) The stacked member is fixedly installed in a housing having a vacuum-sealed accommodating space, the refrigeration unit of the stacked member is fixedly connected to a copper sheet partially accommodated in the housing, the other end of the copper sheet is connected to a radiator, and two electrodes are electrically connected to the positive electrode and the negative electrode of a power supply, respectively, so as to obtain the refrigeration system of the embodiment.

Example 7

(1) forming a first piezoelectric layer with a thickness of 50 nm on a first ferroelectric layer with a thickness of 60 nm by laser pulse deposition at 700 deg.C and a laser energy density of 2mJ/cm²The oxygen pressure is 0.8mbar, the oxygen pressure is changed into 80mbar after deposition is finished, and static oxygen pressure in-situ annealing is carried out to reduce the temperature to room temperature, so that a first refrigeration unit is obtained; wherein the material of the first ferroelectric layer is Barium Titanate (BTO), and the material of the first piezoelectric layer is lead magnesium niobate titanate [ (PbMg)_0.33Nb_0.67O₃)_1-x:(PbTiO₃)_x，x＝0.3]。

(2) And respectively blocking one end of the first piezoelectric layer, which is far away from the first ferroelectric layer, and one end of the first ferroelectric layer, which is far away from the first ferroelectric layer, by using a first baffle plate and a second baffle plate, and respectively depositing an electrode with the thickness of 70 nanometers on the surface of the first piezoelectric layer, which is far away from the first ferroelectric layer, and the surface of the first ferroelectric layer, which is far away from the first ferroelectric layer, by adopting a method of bombarding a metal target by using pulsed laser. The process parameters of depositing the electrode on the surface of the first piezoelectric layer far away from the first ferroelectric layer are as follows: at room temperature, vacuum degree of-5 mbar, energy of 1.5mJ/cm²The pulse number is 10000, and the material is gold; the process parameters for depositing the electrode on the surface of the first ferroelectric layer away from the first piezoelectric layer are as follows: at room temperature, vacuum degree of-5 mbar, energy of 1.5mJ/cm²The number of pulses is 10000, and the material is nonmagnetic steel.

(3) Forming a second ferroelectric layer with a thickness of 50 nm on the electrode close to the ferroelectric layer of the first refrigeration unit and the second baffle by using a laser pulse deposition method, wherein the temperature is 700 ℃ and the laser energy density is 2mJ/cm in the laser pulse deposition process²Oxygen pressureThe oxygen pressure is 0.8mbar, after the deposition is finished, the oxygen pressure is changed to 80mbar, and the static oxygen pressure in-situ annealing is carried out to reduce the temperature to the room temperature; wherein, the material of the second ferroelectric layer is Barium Titanate (BTO).

(4) Forming a second piezoelectric layer with a thickness of 30 nm on the second ferroelectric layer by laser pulse deposition at 700 deg.C and laser energy density of 2mJ/cm²The oxygen pressure is 0.8mbar, the oxygen pressure is changed into 80mbar after the deposition is finished, and the static oxygen pressure in-situ annealing is carried out to reduce the temperature to the room temperature, so that a second refrigeration unit is obtained; wherein the material of the second piezoelectric layer is lead magnesium niobate titanate [ (PbMg)_0.33Nb_0.67O₃)_1-x:(PbTiO₃)_x，x＝0.3]。

(5) And then depositing an electrode with the thickness of 70 nanometers on the surface, provided with the third baffle, of the second piezoelectric layer by using a method of bombarding the metal target by using pulsed laser, wherein the electrode is positioned corresponding to the electrode close to the first piezoelectric layer. The process parameters of depositing the electrode on the surface of the second piezoelectric layer provided with the third baffle are as follows: at room temperature, vacuum degree of-5 mbar, energy of 1.5mJ/cm²The number of pulses was 10000, and the material was gold.

(6) And removing the first baffle, the second baffle and the third baffle to obtain a laminated member consisting of the three electrodes, the first refrigerating unit and the second refrigerating unit, respectively coating silver glue on two sides of the laminated member to form a first conductive piece and a second conductive piece so that the first conductive piece is electrically connected with the electrode close to the first piezoelectric layer and the electrode close to the second ferroelectric layer, and the second conductive piece is electrically connected with the middle electrode to obtain the refrigerating element.

(7) The stacked member formed with the first conductive member and the second conductive member is fixedly installed in a housing having a vacuum-sealed accommodating space, the refrigeration unit of the stacked member is fixedly connected with a copper sheet partially accommodated in the housing, the other end of the copper sheet is connected with a radiator, and the first conductive member and the second conductive member are respectively communicated with a positive electrode and a negative electrode of a power supply, so that the refrigeration system of the embodiment is obtained.

Example 8

(1) forming a first piezoelectric layer with the thickness of 30 nanometers on the first ferroelectric layer with the thickness of 30 nanometers by adopting a laser pulse deposition method, wherein the temperature is 800 ℃ and the laser energy density is 1.5mJ/cm in the laser pulse deposition process²The oxygen pressure is 0.0013mbar, after deposition is finished, the oxygen pressure is changed into 40mbar, and static oxygen pressure in-situ annealing is carried out to reduce the temperature to room temperature, so that a first refrigeration unit is obtained; wherein the material of the first ferroelectric layer is lead zirconate titanate (Pb)_0.3Zr_0.7TiO₃) The material of the first piezoelectric layer is lead magnesium niobate titanate [ (PbMg)_0.33Nb_0.67O₃)_1-x:(PbTiO₃)_x，x＝0.1]。

(2) And respectively blocking one end of the first piezoelectric layer, which is far away from the first ferroelectric layer, and one end of the first ferroelectric layer, which is far away from the first ferroelectric layer, by using a first baffle plate and a second baffle plate, and then respectively depositing an electrode with the thickness of 60 nanometers and an electrode with the thickness of 70 nanometers on one surface of the first piezoelectric layer, which is far away from the first ferroelectric layer, and one surface of the first ferroelectric layer, which is far away from the first piezoelectric layer, by adopting a method of bombarding metal targets by using pulsed laser. The process parameters of depositing the electrode on the surface of the first piezoelectric layer far away from the first ferroelectric layer are as follows: at room temperature, vacuum degree of-5 mbar and energy of 3mJ/cm²The pulse number is 50, and the material is platinum; the process parameters for depositing the electrode on the surface of the first ferroelectric layer away from the first piezoelectric layer are as follows: at room temperature, vacuum degree of-5 mbar and energy of 3mJ/cm²The number of pulses is 50 and the material is platinum.

(3) Forming a second barrier with a thickness of 30 nm on the electrode and the second barrier close to the ferroelectric layer of the first refrigeration unit by laser pulse depositionThe ferroelectric layer is deposited at 600 deg.C and laser energy density of 2.5mJ/cm during laser pulse deposition²The oxygen pressure is 1.3mbar, after the deposition is finished, the oxygen pressure is changed to 30mbar, and the static oxygen pressure in-situ annealing is carried out to reduce the temperature to the room temperature; wherein the material of the second ferroelectric layer is lead zirconate titanate (Pb)_0.3Zr_0.7TiO₃)。

(4) Forming a second piezoelectric layer with a thickness of 30 nm on the second ferroelectric layer by laser pulse deposition at 850 deg.C and laser energy density of 1.9mJ/cm²After the deposition is finished, the oxygen pressure is changed to 30mbar, and the static oxygen pressure in-situ annealing is carried out to reduce the temperature to the room temperature, so as to obtain a second refrigeration unit; wherein the material of the second piezoelectric layer is lead magnesium niobate titanate [ (PbMg)_0.33Nb_0.67O₃)_1-x:(PbTiO₃)_x，x＝0.3]。

(5) And then an electrode with the thickness of 60 nanometers is deposited on the surface, provided with the third baffle, of the second piezoelectric layer, and the position of the electrode corresponds to the position of the electrode close to the piezoelectric layer of the first refrigeration unit. The process parameters of depositing the electrode on the surface of the second piezoelectric layer provided with the third baffle are as follows: at room temperature, vacuum degree of-5 mbar, energy of 2mJ/cm²The pulse number is 500, and the material is magnesium aluminum alloy.

(6) Forming a third ferroelectric layer with a thickness of 30 nm on the electrode of the second ferroelectric layer and the third baffle by laser pulse deposition at 850 deg.C and laser energy density of 2.2mJ/cm²The oxygen pressure is 0.7mbar, after the deposition is finished, the oxygen pressure is changed to 30mbar, and the static oxygen pressure in-situ annealing is carried out to reduce the temperature to the room temperature; wherein the third ferroelectric layer is made of lead zirconate titanate (Pb)_0.3Zr_0.7TiO₃)。

(7) In the first placeForming a third piezoelectric layer with a thickness of 30 nm on the ferroferric oxide layer by adopting a laser pulse deposition method, wherein the temperature is 700 ℃ and the laser energy density is 1.8mJ/cm in the laser pulse deposition process²After the deposition is finished, the oxygen pressure is changed to 30100mbar, and the static oxygen pressure in-situ annealing is carried out to cool the temperature to the room temperature, so as to obtain a third refrigeration unit; wherein the third piezoelectric layer is made of lead magnesium niobate titanate [ (PbMg)_0.33Nb_0.67O₃)_1-x:(PbTiO₃)_x，x＝0.3]。

(8) And then an electrode with the thickness of 60 nanometers is deposited on the surface, provided with the fourth baffle, of the third piezoelectric layer, and the position of the electrode corresponds to the position of the electrode close to the first ferroelectric layer. The process parameters of depositing the electrode on the surface of the third piezoelectric layer provided with the fourth baffle are as follows: at room temperature, vacuum degree of-5 mbar, energy of 2.5mJ/cm²The number of pulses was 5000, and the material was platinum.

(9) And removing the first baffle, the second baffle, the third baffle and the fourth electrode to obtain a laminated member consisting of the four electrodes, the first refrigerating unit, the second refrigerating unit and the third refrigerating unit, respectively coating silver glue on two sides of the laminated member to respectively form a first conductive piece and a second conductive piece, electrically connecting the electrode close to the first piezoelectric layer and the electrode close to the second ferroelectric layer by the first conductive piece, and electrically connecting the electrode close to the first ferroelectric layer and the electrode close to the third ferroelectric layer by the second conductive piece to obtain the refrigerating element.

(10) The stacked member formed with the first conductive member and the second conductive member is fixedly installed in a housing having a vacuum-sealed accommodating space, the refrigeration unit of the stacked member is fixedly connected with a copper sheet partially accommodated in the housing, the other end of the copper sheet is connected with a radiator, and the first conductive member and the second conductive member are respectively communicated with a positive electrode and a negative electrode of a power supply, so that the refrigeration system of the embodiment is obtained.

Example 9

(1) forming a piezoelectric layer with a thickness of 50 nm on the ferroelectric layer with a thickness of 50 nm by laser pulse deposition at 700 deg.C and laser energy density of 2mJ/cm²After the deposition is finished, changing the oxygen pressure to 100mbar, and carrying out static oxygen pressure in-situ annealing to reduce the temperature to room temperature to obtain a refrigeration unit; wherein the ferroelectric layer is made of barium titanate, and the piezoelectric layer is made of lead zirconate titanate (Pb)_0.5Zr_0.5TiO₃)。

Example 10

(1) forming a piezoelectric layer with a thickness of 50 nm on the ferroelectric layer with a thickness of 50 nm by laser pulse depositionBulk layer, laser pulse deposition at 700 deg.C and laser energy density of 2mJ/cm²After the deposition is finished, changing the oxygen pressure to 100mbar, and carrying out static oxygen pressure in-situ annealing to reduce the temperature to room temperature to obtain a refrigeration unit; wherein the material of the ferroelectric layer is bismuth ferrite, and the material of the piezoelectric layer is lead zirconium titanate (Pb)_0.8Zr_0.2TiO₃)。

Example 11

(1) forming a piezoelectric layer with a thickness of 50 nm on the ferroelectric layer with a thickness of 50 nm by laser pulse deposition at 700 deg.C and laser energy density of 2mJ/cm²After the deposition is finished, changing the oxygen pressure to 100mbar, and carrying out static oxygen pressure in-situ annealing to reduce the temperature to room temperature to obtain a refrigeration unit; wherein the material of the ferroelectric layer is lead zirconate titanate (Pb)_0.4Zr_0.6TiO₃) The piezoelectric layer is made of lead magnesium niobate titanate [ (PbMg)_0.33Nb_0.67O₃)_1-x:(PbTiO₃)_x，x＝0.3]。

Example 12

(1) forming a piezoelectric layer with a thickness of 50 nm on the ferroelectric layer with a thickness of 50 nm by laser pulse deposition at 700 deg.C and laser energy density of 2mJ/cm²After the deposition is finished, changing the oxygen pressure to 100mbar, and carrying out static oxygen pressure in-situ annealing to reduce the temperature to room temperature to obtain a refrigeration unit; wherein the ferroelectric layer is made of bismuth ferrite, and the piezoelectric layer is made of lead magnesium niobate titanate [ (PbMg)_0.33Nb_0.67O₃)_1-x:(PbTiO₃)_x，x＝0.3]。

Example 13

(1) respectively evaporating an electrode on two opposite surfaces of a ferroelectric layer with the thickness of 100 nanometers by adopting an ion sputtering instrument to obtain a laminated body, wherein the ferroelectric layer is made of barium titanate; the technological parameters of evaporating the electrode on the ferroelectric layer are as follows: argon atmosphere, ionization time 90 seconds, 2 times of evaporation, thickness of 70 nanometers, and silver as a material.

(2) The stacked member is fixedly installed in a housing having a vacuum-sealed accommodating space, the refrigeration unit of the stacked member is fixedly connected to a copper sheet partially accommodated in the housing, the other end of the copper sheet is connected to a radiator, and two electrodes are electrically connected to the positive electrode and the negative electrode of a power supply, respectively, so as to obtain the refrigeration system of the embodiment.

Example 14

(1) forming a piezoelectric layer with a thickness of 120 nm on the ferroelectric layer with a thickness of 120 nm by laser pulse deposition at 700 deg.C and laser energy density of 2mJ/cm²Oxygen pressure of 0.8mbar, after deposition, oxygen pressure of 100mbarCarrying out static oxygen pressure in-situ annealing to reduce the temperature to room temperature to obtain a refrigeration unit; wherein the ferroelectric layer is made of barium titanate, and the piezoelectric layer is made of lead magnesium niobate titanate [ (PbMg)_0.33Nb_0.67O₃)_1-x:(PbTiO₃)_x，x＝0.3]。

Table 1 shows the adiabatic temperatures of the refrigeration systems of examples 1 to 14.

TABLE 1

As can be seen from table 1, the adiabatic temperatures of the refrigeration systems of examples 1 to 12 were at least 7.5K, while the adiabatic temperatures of the refrigeration systems of examples 13 and 14 were 2K and 4.2K, respectively, and it is apparent that the piezoelectric layer can effectively increase the adiabatic temperature of the refrigeration unit, i.e., increase the adiabatic temperature of the refrigeration system. And as can be seen from table 1, although the thickness of one refrigeration unit of example 1 and the total thickness of two refrigeration units of example 4 are equal, the refrigeration system of example 4 has a higher adiabatic temperature than the refrigeration system of example 3 because the structure of the refrigeration system of the repeated refrigeration units can reduce the leak point, increase the intensity of the voltage allowed to be applied, and thus increase the adiabatic temperature variation amount.

Comparing example 13 with example 1, it can be seen that the adiabatic temperature of example 14 using only barium titanate as the refrigeration unit is only 2K, while the adiabatic temperature of example 1 using the refrigeration unit of the same thickness is as high as 8.6K, whereas the refrigeration system of example 1 differs from that of example 13 only in that the refrigeration unit of example 1 is composed of a ferroelectric layer and a piezoelectric layer, and it is apparent that the addition of the piezoelectric layer can effectively increase the adiabatic temperature of the refrigeration unit.

Comparing example 14 with examples 1 to 3 and examples 9 to 12, it can be seen that although the refrigeration unit of example 14 also consists of one ferroelectric layer and one piezoelectric layer, the insulation temperature is only 4.2K, which is much lower than the insulation temperatures of examples 1 to 3 and examples 9 to 12, which are different from the thickness of the refrigeration unit, because the refrigeration units of examples 1 to 3 and examples 9 to 12 have smaller thicknesses and larger entropy changes, which is beneficial to obtain larger insulation temperature change.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. A refrigeration system, comprising:

the shell is provided with a vacuum sealed accommodating space;

the heat conduction piece is partially accommodated in the shell and is fixedly connected with the refrigeration element, and the heat conduction piece is used for conducting the heat of the refrigeration element to the outside;

the piezoelectric layer is made of lead magnesium niobate titanate;

the ferroelectric layer is made of barium titanate;

the number of the electrodes is two, a plurality of refrigerating units which are sequentially stacked are stacked between the two electrodes, and the sum of the thicknesses of the refrigerating units is not more than 200 nanometers.

2. The refrigeration system of claim 1, wherein the thickness of the electrode is between 20 nanometers and 120 nanometers.

3. The refrigeration system of claim 2 wherein the piezoelectric layer is formed by laser pulse deposition.

4. The refrigeration system of claim 1 wherein the thermally conductive member is copper.

5. The refrigeration system of claim 1, wherein the sum of the thicknesses of the plurality of refrigeration units is between 10 nanometers and 200 nanometers.

6. The refrigeration system of claim 1, further comprising a heat sink disposed outside the housing, the heat sink being fixedly coupled to the heat transfer element.

7. The refrigeration system of claim 1 wherein a reflective film is disposed on an inner surface of the housing.

8. The refrigeration system of claim 7, wherein the reflective film is an aluminum or tin film.

9. The refrigeration system of claim 1 wherein the electrode material is selected from one of copper, aluminum, indium, platinum, silver, gold, and a non-magnetic alloy.

10. The refrigerant system as set forth in claim 9, wherein said non-magnetic alloy is steel, magnesium aluminum alloy, platinum tin alloy.