Lithium niobate thin film temperature sensor, temperature measurement method and temperature measurement device

Abstract

The present application discloses a lithium niobate thin film temperature sensor, a temperature measurement method and a temperature measurement device. The ultrasonic piezoelectric material of the temperature sensor is a lithium niobate piezoelectric coating, and the temperature to be measured is characterized by at least one of the surface cross-sectional morphology, grain shape and size, crystal structure, and ultrasonic morphology of the coating. In order to achieve real-time temperature measurement of the lithium niobate thin film temperature sensor, the present application also provides a temperature measurement device, including a heating area, a thin film ultrasonic temperature sensor, a pulse transmitter-receiver, a controller, and a computer terminal device that are electrically connected in sequence. The present technical solution provides a monitoring device and a thin film temperature sensor that can work stably within a wide temperature range, monitor the temperature in real time, realize early warning of temperature changes, and avoid structural damage to important equipment.

Description

Technical Field

[0001] The present application relates to the technical field of temperature measurement, and in particular to a lithium niobate thin film temperature sensor, a temperature measurement method and a temperature measurement device. Background Art

[0002] Nuclear power plant fasteners, aerospace engines, etc. work under high temperature, high pressure, high load, and high speed for a long time, which will reduce the reliable working life of hot end components, reduce material strength, cause creep and even fracture of hot end materials, and cause serious consequences. Therefore, it is of great significance to accurately measure the temperature of components, realize performance monitoring, life prediction, and reduce accidents caused by high temperature.

[0003] A variety of temperature measurement technologies have been developed for the complex environments inside aircraft engines, nuclear power plants, etc.

[0004] The principle of crystal temperature measurement technology is that crystals irradiated by high-energy particles will produce a large number of lattice defects, which can be gradually eliminated by high-temperature annealing. The residual defect concentration of the material is related to the annealing temperature, and the information of the annealing temperature can be obtained by measuring the residual defect concentration. However, the residual defect concentration is difficult to determine by conventional methods. Therefore, the functional relationship between the influence of the residual defect concentration on the physical properties and the annealing temperature can be established as the basis for temperature measurement. However, this method only measures the highest temperature experienced by the object being measured, and cannot achieve real-time temperature measurement of rotating turbine blades or nuclear power plant fasteners. Moreover, the crystal used needs to be buried in the object being measured, so it is necessary to open a hole on the surface of the object being measured, which will greatly damage the object being measured and reduce its lifespan, and has considerable requirements on the strength of the object being measured.

[0005] The temperature measurement method of temperature-indicating paint is based on the fact that temperature-indicating paint will undergo certain physical and chemical reactions during the temperature increase process, and its molecular composition changes, resulting in color changes, indicating the temperature distribution of the highest temperature on the surface of the measured component. Similarly, this method can only measure the highest temperature of the hot end component, and cannot perform real-time monitoring, and the temperature resolution is low; secondly, irreversible temperature-indicating paint cannot be used continuously, and each temperature measurement requires the blade to be disassembled for painting and interpretation. At the same time, the color change of the temperature-indicating paint will be affected by the heating speed, time, and environmental pollution, resulting in its temperature measurement accuracy being lower than that of general temperature measurement methods. Moreover, the color interpretation process of the temperature-indicating paint is interfered by human experience factors, and the accuracy is low.

[0006] The advantage of fluorescence temperature measurement is that the fluorescence lifetime is only related to temperature and is not affected by any other factors. It has a wide temperature measurement range, good repeatability, and extremely high temperature measurement accuracy, and does not interfere with the temperature field of the measured surface. However, if it is to be applied to the temperature measurement of aircraft engine turbine blades, the problem of fluorescent materials and coupling must be solved.

[0007] Radiation temperature measurement technology is a method of collecting the thermal radiation emitted by the surface of the object being measured to obtain the temperature value. However, it is easy to lose radiation due to absorption by gases in the air, and it is also easily affected by the reflected radiation from other objects. The temperature measurement accuracy needs to be further improved.

[0008] Therefore, it is necessary to develop more effective real-time temperature measurement technology to obtain the temperature field distribution of nuclear power plant fasteners and aerospace engine blades to achieve real-time temperature monitoring. Summary of the invention

[0009] In view of this, the present application provides a lithium niobate thin film temperature sensor, a temperature measurement method and a temperature measurement device, which can reflect the influence of the measured temperature through changes in at least one of the surface cross-sectional morphology, grain shape and size, crystal structure, and ultrasonic morphology of the lithium niobate piezoelectric coating, and thus accurately and in real time feedback the temperature changes.

[0010] In a first aspect, the present application provides a lithium niobate thin film temperature sensor, the main functional layer of which is a lithium niobate piezoelectric coating, and the piezoelectric coating is configured to be able to characterize the temperature to be measured through at least one of the surface cross-sectional morphology, grain shape and size, crystal structure, and ultrasonic morphology of the coating.

[0011] As used herein, "crystal structure" includes, but is not limited to, crystal orientation, diffraction peak intensity, and half-width.

[0012] As used herein, "ultrasound modality" includes, but is not limited to, ultrasonic signal, time of flight, and sound wave frequency.

[0013] Suitably but not restrictively, the lithium niobate thin film temperature sensor is a composite thin film of a multi-layer coating, which includes, starting from a substrate, a bonding layer, a piezoelectric layer, a first protective layer, a second protective layer, a transition layer, and an electrode layer.

[0014] In this way, the multilayer structure technology is expected to inhibit the growth of lithium niobate columnar crystals and improve the density, adhesion and corrosion resistance of the coating. The piezoelectric coating is a single layer of homogeneous lithium niobate.

[0015] In a second aspect, the present application provides a temperature measurement method, which is implemented using the lithium niobate thin film temperature sensor as described above.

[0016] Suitable but not limiting, the implementation process includes the following steps:

[0017] (1) providing the lithium niobate thin film temperature sensor coated on the object to be measured, wherein the lithium niobate thin film temperature sensor comprises a bonding layer, the piezoelectric coating, a first protective layer, a second protective layer, a transition layer and an electrode layer which are sequentially stacked on a substrate, and an electrode gap (gap width 0.5 mm-2 mm) between a ground electrode and a surface electrode is prepared by ion beam etching. Only one electrode layer is deposited to realize the preparation of a ground electrode and a surface electrode double electrode;

[0018] (2) subjecting the object to be tested and the lithium niobate thin film temperature sensor to heat treatment;

[0019] (3) measuring at least one of the surface cross-sectional morphology, grain shape and size, crystal structure, and ultrasonic morphology of the piezoelectric coating;

[0020] (4) The temperature to be measured is obtained based on at least one of the surface cross-sectional morphology, grain shape and size, crystal structure, and ultrasonic morphology.

[0021] Suitably but not restrictively, the bonding layer, the lithium niobate piezoelectric coating, the first protective layer, the second protective layer, the transition layer, and the electrode layer are prepared by radio frequency magnetron sputtering.

[0022] Suitably but not restrictively, the piezoelectric coating is 10-20 microns thick, and the deposition parameters are as follows: the power of RF magnetron sputtering is 500-1000W, the deposition gas pressure is 0.5-5Pa, Ar / O2 is 1 / 2-5 / 1, the chamber temperature is 80-250°C, the deposition time is 2h-10h, and the distance between the target and the substrate is 2cm-7cm.

[0023] Suitably but not restrictively, the bonding layer is Ti or Cr, which increases the bonding force between the piezoelectric layer and the substrate and prevents high-temperature shedding. The thickness is 50-200 nanometers, and the deposition parameters are as follows: using high-purity Cr or Ti target material, RF power is 500-1000W, deposition pressure is 1-3Pa, pure argon gas, chamber temperature is 100-300°C, deposition time is 1min-10min, and the distance between the target material and the substrate is 3cm-10cm.

[0024] The first protective layer is SiO2, which increases the total resistance of the sensor and prevents high-voltage breakdown. It is 2-5 microns thick and the deposition parameters are as follows: use high-purity Si target material, RF power is 700-1000W, deposition pressure is 1-3Pa, Ar / O2 is 1 / 2-4 / 1, chamber temperature is 100-300℃, deposition time is 2h-5h, and the distance between the target and the substrate is 3cm-7cm.

[0025] The second protective layer is Cr, which enhances the adhesion between the coatings. It is 50-200 nanometers thick and the deposition parameters are as follows: high-purity Cr target, RF power of 500-1000W, deposition pressure of 1-3Pa, pure argon, chamber temperature of 100-300°C, deposition time of 1min-10min, and the distance between the target and the substrate of 3cm-10cm.

[0026] The transition layer is AgCr, which is an interlayer between the Cr protective layer and the electrode layer to increase the adhesion to Cr. It is 50-200 nanometers thick and the deposition parameters are as follows: use a mixed target material of Ag:Cr=1:9~1:1, RF power of 500-1000W, deposition pressure of 1-3Pa, pure argon, chamber temperature of 100-300℃, deposition time of 1min-10min, and the distance between the target and the substrate of 3cm-10cm.

[0027] The electrode layer is Ag or Ti or Cr or AgCr to increase conductivity, with a thickness of 10-30 microns. The deposition parameters are as follows: using high-purity Ag or Ti or Cr targets or mixed targets of Ag:Cr=1:9~1:1, RF power is 500-1000W, deposition pressure is 0.5-5Pa, Ar / O2 is 1 / 2-5 / 1, chamber temperature is 80-250℃, deposition time is 2h-10h, and the distance between target and substrate is 2cm-7cm.

[0028] Suitable but not limiting, the temperature rise rate of the heat treatment is 2°C / min-5°C / min, and the maximum temperature is 400-1000°C.

[0029] Suitable but not restrictive, by measuring the changes in the surface cross-sectional morphology, grain shape / size, crystal structure, and ultrasonic morphology of the coating, the substrate or ambient temperature can be fed back in real time, and the feasibility of measuring the duration of the object under test at a specific ambient temperature can be achieved.

[0030] The specific operation and principle of the ultrasonic measurement are as follows: voltage is applied to the thin film sensor through a pulse transmitter-receiver. Under the action of the piezoelectric effect, the sensor deforms and stimulates the emission wave. The emission wave propagates back and forth in the object to be measured. The wave returning from the bottom is called a reflected wave. The reflected wave signal is converted into an electrical signal by the sensor and received by the pulse transmitter-receiver. Since the object to be measured will expand and contract when it is at different ambient temperatures, the distance of sound wave movement and signal strength will be changed. Therefore, it is only necessary to measure the reflected ultrasonic signal and the time difference between multiple reflected waves (i.e., flight time) to obtain the ambient temperature and duration of the object to be measured, and realize online temperature monitoring.

[0031] In a third aspect, the present application provides a temperature measurement device, comprising a heating area, a thin film temperature sensor, a pulse transmitter-receiver, a controller, and a computer terminal device electrically connected in sequence, wherein the thin film temperature sensor is such as the above-mentioned lithium niobate thin film temperature sensor.

[0032] This application has the following advantages and beneficial effects:

[0033] First, the selected temperature sensing material is LiNbO3, which is the ferroelectric material with the largest spontaneous polarization intensity and the highest Curie temperature known so far. It has the advantages of high operating temperature (1110°C) and large d33 value (~39pC / N), which can simultaneously meet the high temperature environment and high-energy ultrasonic requirements of nuclear power plants and aerospace sensors.

[0034] Second, the temperature sensing material used in this application is a LiNbO3 film, which is about 10 microns to 20 microns thick. Compared with the fluorescence temperature measurement method, the technology of this application does not have a coupling problem. Compared with the crystal temperature measurement technology, the technology of this application has a higher adhesion to the substrate and the object to be measured than the crystal. Secondly, because the film is directly grown on the object to be measured, there is no need to open holes for burying, and it will not cause damage to the structure of the object to be measured. There is no requirement for the strength of the object to be measured, and no additional adhesive is required to achieve temperature monitoring.

[0035] Third, the film used in this application is deposited on the object to be tested by radio frequency magnetron technology. Compared with thin film preparation technologies such as laser pulse deposition, electron beam evaporation, and sol-gel method, radio frequency sputtering is a more mature piezoelectric film preparation technology. Its preparation temperature is low, it will not affect the mechanical properties of the substrate, and the deposition parameters can be adjusted to obtain piezoelectric film materials with preferential orientation.

[0036] Fourth, the lithium niobate thin film temperature sensor of the present application includes a bonding layer, a piezoelectric coating, a first protective layer, a second protective layer, a transition layer and an electrode layer stacked on a substrate in sequence, and an electrode gap between a ground electrode and a surface electrode is prepared by ion beam etching. Multilayer composite is expected to inhibit the growth of lithium niobate columnar crystals and improve the density, adhesion and corrosion resistance of the coating. The existence of the electrode gap makes it possible to complete the preparation of the ground electrode and the surface electrode by depositing only one electrode layer.

[0037] Fifth, the measurement targets used in this application to measure temperature changes are coating surface / cross-section morphology, grain shape / size, crystal structure, and ultrasonic morphology. Compared with the temperature-indicating paint temperature measurement method, the measurement results of this application are all obtained through measuring instruments, avoiding interference from human factors and having high accuracy. Compared with radiation temperature measurement technology, it is not affected by other environmental factors such as air and surrounding objects.

[0038] Sixth, the technology of the present application measures the changes in the coating surface cross-sectional morphology, grain shape and size, crystal structure, and ultrasonic morphology to provide real-time feedback on the substrate / ambient temperature and realize the feasibility of measuring the duration of the object to be tested at a specific ambient temperature.

[0039] Seventh, the present application scheme provides a monitoring device that can operate stably within a wide temperature range, monitor the temperature in real time, realize early warning of temperature changes, and avoid structural damage to important equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The technical solution and other beneficial effects of the present application will be made apparent by describing in detail the specific implementation methods of the present application in conjunction with the accompanying drawings.

[0041] Figure 1 (a)-(b) is a schematic diagram of the structure of the lithium niobate composite film temperature sensor and the real-time temperature measurement method and equipment of the present application.

[0042] Figure 2 (a)-(b) are the feedback of the crystal structure and half-width of the diffraction peak to temperature in Example 2.

[0043] Figure 3 This is the feedback of grain morphology and size on temperature in Example 3.

[0044] 4(a)-(c) show the feedback of the ultrasonic signal, flight time, and sound wave frequency on the temperature in Example 4.

[0045] Figure 5 This is the feedback of the crystal structure and half-width of the diffraction peak on time in Example 5.

[0046] Figure 6 This is the feedback of the ultrasonic signal on time in Example 5.

[0047] Figure 7 This is the feedback of the sound wave frequency on time in Example 5.

[0048] The components in the figure are marked as follows:

[0049] 1-heating area, 2-test object, 3-thin film temperature sensor, 4-ground electrode, 5-surface electrode, 6-electrode gap, 7-pulse transmitter-receiver, 8-controller, 9-computer terminal equipment DETAILED DESCRIPTION

[0050] For a better understanding of the present invention, the following examples are provided to further illustrate the present invention, but the present invention is not limited to the following examples.

[0051] Embodiment 1:

[0052] (1) Preparation of lithium niobate thin film temperature sensor: radio frequency magnetron sputtering technology is used to deposit various functional layers on the surface of the object to be tested to form a temperature sensor integrated with the object to be tested; (compared with fluorescent materials, the coating is not easy to fall off and there is no coupling problem)

[0053] (2) Transfer the object to be tested and the thin film integrated temperature sensor to a high temperature annealing furnace for heat treatment. Set the temperature rise rate and maximum temperature of the annealing furnace;

[0054] (3) Measure the changes of surface and cross-sectional morphology of thin film temperature sensors with temperature;

[0055] (4) Measure the change of grain shape and size of thin film temperature sensor with temperature;

[0056] (5) Measure the change of crystal structure of thin film temperature sensor with temperature;

[0057] (6) Measure the change of ultrasonic morphology of thin film temperature sensor with temperature;

[0058] (7) Combine the coating surface cross-sectional morphology, grain shape and size, crystal structure, and ultrasonic morphology changes to achieve the goal of real-time temperature feedback.

[0059] Preferably, the lithium niobate thin film temperature sensor is a composite film with a multi-layer coating, as shown in Figure 1(a), starting from the substrate, it includes a bonding layer, a piezoelectric layer, a first protective layer, a second protective layer, a transition layer, and an electrode layer. The multi-layer structure technology is expected to inhibit the growth of lithium niobate columnar crystals and improve the density, adhesion, and corrosion resistance of the coating; the piezoelectric coating is a single layer of homogeneous lithium niobate; and the electrode gap between the ground electrode and the surface electrode is prepared by ion beam etching (the gap width is 0.5mm-2mm), and only one electrode layer is deposited to achieve the preparation of the ground electrode and the surface electrode double electrode.

[0060] Preferably, the bonding layer, lithium niobate piezoelectric coating, protective layer, transition layer and electrode layer are prepared by radio frequency magnetron sputtering.

[0061] Preferably, the lithium niobate film is 10-20 microns thick, and the deposition parameters are as follows: RF (radio frequency magnetron sputtering) power is between 500-1000W, deposition gas pressure is between 0.5-5Pa, Ar / O2 is between 1 / 2-5 / 1, chamber temperature is between 80-250°C, deposition time is between 2h-10h, and the distance between the target and the substrate is between 2cm-7cm.

[0062] Preferably, the bonding layer is Ti or Cr to increase the bonding force between the piezoelectric layer and the substrate and prevent high-temperature shedding. The thickness is 50-200 nanometers, and the deposition parameters are as follows: use high-purity Cr or Ti target material, RF power is 500-1000W, deposition pressure is 1-3Pa, pure argon gas, chamber temperature is 100-300°C, deposition time is 1min-10min, and the distance between the target and the substrate is 3cm-10cm.

[0063] Preferably, the first protective layer is SiO2, which increases the total resistance of the sensor and prevents high-voltage breakdown. It is 2-5 microns thick and the deposition parameters are as follows: use high-purity Si target material, RF power is 700-1000W, deposition pressure is 1-3Pa, Ar / O2 is 1 / 2-4 / 1, chamber temperature is 100-300°C, deposition time is 2h-5h, and the distance between the target and the substrate is 3cm-7cm.

[0064] Preferably, the second protective layer is Cr to enhance the adhesion between the coatings, with a thickness of 50-200 nanometers, and the deposition parameters are as follows: use high-purity Cr target material, RF power of 500-1000W, deposition pressure of 1-3Pa, pure argon gas, chamber temperature of 100-300°C, deposition time of 1min-10min, and the distance between the target and the substrate of 3cm-10cm.

[0065] Preferably, the transition layer is AgCr, which is an interlayer between the Cr protective layer and the electrode layer to increase the adhesion to Cr, with a thickness of 50-200 nanometers. The deposition parameters are as follows: using a mixed target material of Ag:Cr=1:9~1:1, an RF power of 500-1000W, a deposition pressure of 1-3Pa, pure argon, a chamber temperature of 100-300°C, a deposition time of 1min-10min, and a distance between the target and the substrate of 3cm-10cm.

[0066] Preferably, the electrode layer is Ag or Ti or Cr or AgCr to increase conductivity, with a thickness of 10-30 microns. The deposition parameters are as follows: using high-purity Ag or Ti or Cr targets or mixed targets of Ag:Cr=1:9~1:1, RF (radio frequency magnetron sputtering) power between 500-1000W, deposition pressure between 0.5-5Pa, pure argon, chamber temperature between 80-250°C, deposition time between 2h-10h, and the distance between the target and the substrate between 2cm-7cm.

[0067] Preferably, the annealing furnace temperature rise rate is between 2°C / min-5°C / min, and the maximum temperature is between 400-1000°C;

[0068] Preferably, by measuring the changes in the coating surface cross-sectional morphology, grain shape and size, crystal structure, and ultrasonic morphology, the substrate / ambient temperature can be fed back in real time, and the feasibility of measuring the duration of the object to be tested at a specific ambient temperature can be achieved.

[0069] Suitable but not limiting, crystal structure analysis includes crystal orientation, diffraction peak intensity, and half-height width.

[0070] Suitably but not limitingly, the ultrasound morphology analysis includes ultrasound signal, flight time, sound wave frequency.

[0071] Please refer to Figure 1(b). In order to realize real-time temperature measurement of the lithium niobate thin film temperature sensor, the present application also provides a set of testing equipment, including a heating area 1, a thin film temperature sensor 3, a pulse transmitter-receiver 7, a controller 8 and a computer terminal device 9 electrically connected in sequence. The thin film temperature sensor 3 is such as the above-mentioned lithium niobate thin film temperature sensor.

[0072] As described above, the thin film temperature sensor 3 has an electrode layer, which includes a ground electrode 4 and a surface electrode 5, and an electrode gap 6 is provided between the electrode 4 and the surface electrode 5. The surface electrode 5 is used to electrically connect the pulse transmitter-receiver 7, and the ground electrode 4 is used to be grounded.

[0073] The heating area 1 is used to heat the object to be measured 2 .

[0074] The object to be measured 2 is placed between the heating area 1 and the thin film temperature sensor 3 .

[0075] Here, the computer terminal device 9 may be equipped with auxiliary tools including but not limited to LabView software. The computer terminal device 9 may be a PC, or a tablet computer, etc.

[0076] The specific operation and principle of the ultrasonic measurement are as follows: voltage is applied to the thin film sensor through a pulse transmitter-receiver. Under the action of the piezoelectric effect, the sensor deforms and stimulates the emission wave. The emission wave propagates back and forth in the object to be measured. The wave returning from the bottom is called a reflected wave. The reflected wave signal is converted into an electrical signal by the sensor and received by the pulse transmitter-receiver. Since the object to be measured will expand and contract when it is at different ambient temperatures, the distance of sound wave movement and signal strength will be changed. Therefore, it is only necessary to measure the reflected ultrasonic signal and the time difference between multiple reflected waves (i.e., flight time) to obtain the ambient temperature and duration of the object to be measured, and realize online temperature monitoring.

[0077] Embodiment 2:

[0078] The present invention provides a lithium niobate thin film temperature sensor and a real-time temperature measurement method thereof. The temperature sensor material used is a single-layer homogeneous lithium niobate piezoelectric coating. The substrate / ambient temperature is fed back in real time through changes in the coating surface / cross-sectional morphology, grain shape / size, crystal structure, and ultrasonic morphology.

[0079] Combination Figure 2, a piezoelectric coating was deposited on a stainless steel sheet, and the feasibility of real-time monitoring of the coating's crystal structure and diffraction peak half-width to temperature was verified.

[0080] (1) Preparation of lithium niobate thin film temperature sensor: A lithium niobate thin film and an electrode layer were deposited on the surface of the object to be tested by radio frequency magnetron sputtering technology to form a temperature sensor integrated with the object to be tested; (lithium niobate thin film deposition parameters are as follows: RF power is 900 W, deposition pressure is 2 Pa, Ar / O2 is 2 / 1, chamber temperature is 235 ° C, deposition time is 8 h, and the distance between the target and the substrate is 5 cm.)

[0081] (2) Transfer the object to be tested and the thin film integrated temperature sensor to a high temperature annealing furnace for heat treatment: set the annealing furnace temperature rise rate to 5°C / min and the maximum temperature to 800°C;

[0082] (3) Measure the change of crystal structure of thin film temperature sensor with temperature;

[0083] (4) Combined with the changes in the coating crystal structure, the goal of real-time temperature feedback is achieved.

[0084] The crystal structure and half-width of the diffraction peak of the thin film temperature sensor change with temperature. Figure 2 (a), 2(b), Figure 2 (a) It can be seen that as the ambient temperature of the stainless steel sheet increases, the crystal structure of the lithium niobate film changes greatly. The peak intensities of most diffraction peaks increase, such as (012), (024), (116), (214), etc. At the same time, when the temperature is higher than 500°C, the (002) peak disappears. Figure 2 (b) It can be seen that as the ambient temperature of the stainless steel sheet increases, the half-height widths of the (012), (116), and (214) diffraction peaks gradually decrease, which means that the grain size becomes larger. Therefore, the ambient temperature of the object to be tested can be determined by the changes in the peak intensity and half-height width of each diffraction peak.

[0085] Embodiment three:

[0086] The present invention provides a lithium niobate thin film temperature sensor and a real-time temperature measurement method thereof. The temperature sensor material used is a single-layer homogeneous lithium niobate piezoelectric coating. The substrate / ambient temperature is fed back in real time through changes in the coating surface / cross-sectional morphology, grain shape / size, crystal structure, and ultrasonic morphology.

[0087] Combination Figure 3 , a piezoelectric coating was deposited on a Si wafer, and the feasibility of real-time monitoring of the coating surface / cross-sectional morphology and grain shape / size on the temperature was verified.

[0088] (1) Preparation of lithium niobate thin film temperature sensor: A lithium niobate thin film and an electrode layer were deposited on the surface of the object to be tested by radio frequency magnetron sputtering technology to form a temperature sensor integrated with the object to be tested; (lithium niobate thin film deposition parameters are as follows: RF power is 900 W, deposition pressure is 2 Pa, Ar / O2 is 2 / 1, chamber temperature is 150 ° C, deposition time is 6 h, and the distance between the target and the substrate is 5 cm.)

[0089] (2) Transfer the object to be tested and the thin film integrated temperature sensor to a high temperature annealing furnace for heat treatment: set the annealing furnace temperature rise rate to 5°C / min and the maximum temperature to 800°C;

[0090] (3) Measure the changes of surface / cross-sectional morphology and grain shape / size of thin film temperature sensor coating with temperature;

[0091] (4) Combine the coating surface / cross-section morphology and grain shape / size changes to achieve the goal of real-time temperature feedback.

[0092] The surface morphology and grain shape / size of thin film temperature sensors change with temperature. Figure 3 . As the annealing temperature increases, the coating surface morphology and grain morphology are obviously different, and the grain size is also different. When the thin film temperature sensor is at room temperature, the surface is flat, the grains are spherical, and the particle size is between 200nm-500nm; when the ambient temperature increases to 500℃, a very obvious secondary crystallization phenomenon occurs, and the regenerated grains are irregular, the particle size is much smaller than the initial grains, and the particle size is uneven; when the ambient temperature increases to 600℃, the size of the small grains generated by secondary crystallization increases, the particle size is about 300nm, and it presents an angular polyhedron shape. Therefore, the ambient temperature of the object to be measured can be judged by the changes in surface morphology and grain shape / size.

[0093] Embodiment 4:

[0094] Combined with Figure 4(a)-(c), the coating was deposited on a chromium-nickel-inconel superalloy M9 bolt and a stainless steel sheet, and the feasibility of real-time monitoring of the temperature by the coating ultrasonic signal, flight time, and sound wave frequency was verified.

[0095] (1) Preparation of lithium niobate thin film temperature sensor: A lithium niobate thin film and an electrode layer are deposited on the surface of the object to be tested by radio frequency magnetron sputtering technology to form a temperature sensor integrated with the object to be tested; (The lithium niobate thin film deposition parameters are as follows: RF power is 900 W, deposition pressure is 2 Pa, Ar / O2 is 2 / 1, chamber temperature is 150 ° C, deposition time is 8 h, and the distance between the target and the substrate is 5 cm. The electrode layer deposition parameters are as follows: RF power is 800 W, deposition pressure is 2 Pa, chamber temperature is 120 ° C, deposition time is 2 h, and the distance between the target and the substrate is 4 cm.)

[0096] (2) Transfer the object to be tested and the thin film integrated temperature sensor to a high temperature annealing furnace for heat treatment: set the annealing furnace temperature rise rate to 5°C / min and the maximum temperature to 800°C;

[0097] (3) Measure the ultrasonic signal excited by the thin film temperature sensor on the chromium-nickel-inconel superalloy M9 bolt, the flight time, and the sound wave frequency of the stainless steel sheet sensor as a function of temperature;

[0098] (4) Combine the coating ultrasonic signal, flight time, and sound wave frequency changes to achieve the goal of real-time temperature feedback.

[0099] The variation of the ultrasonic signal, flight time, and sound wave frequency excited by the thin film temperature sensor with temperature is shown in Figure 4. Obviously, when the temperature of the bolt is 500°C, the excited ultrasonic signal is lower than the normal temperature, as shown in Figure 4(a); and as the ambient temperature (i.e., the bolt temperature) rises, the measured flight time also gradually increases, as shown in Figure 4(b). This is because the high temperature causes the bolt to expand, the distance of the sound wave movement increases, the flight time is prolonged, and the higher the ambient temperature, the more violent the bolt expansion; at the same time, as the ambient temperature rises from room temperature to 700°C, the sound wave frequency has a downward trend, as shown in Figure 4(c). Therefore, by comparing the ultrasonic signal, flight time, and sound wave frequency with the normal temperature data, the ambient temperature of the bolt, stainless steel, and other objects to be measured can be fed back.

[0100] Embodiment five:

[0101] The present invention provides a lithium niobate thin film temperature sensor and a real-time temperature measurement method thereof. The temperature sensor material used is a single-layer homogeneous lithium niobate piezoelectric coating. The substrate / ambient temperature is fed back in real time through changes in the coating surface / cross-sectional morphology, grain shape / size, crystal structure, and ultrasonic morphology.

[0102] Combination Figure 5 , Figure 6 , Figure 7 , deposited a piezoelectric coating on a stainless steel sheet, fixed the ambient temperature everywhere, and verified the feasibility of the feedback of the coating crystal structure, ultrasonic signal, and sound wave frequency on time.

[0103] (1) Preparation of lithium niobate thin film temperature sensor: A lithium niobate thin film and an electrode layer are deposited on the surface of the object to be tested by radio frequency magnetron sputtering technology to form a temperature sensor integrated with the object to be tested; (The lithium niobate thin film deposition parameters are as follows: RF power is 900 W, deposition pressure is 2 Pa, Ar / O2 is 2 / 1, chamber temperature is 150 ° C, deposition time is 8 h, and the distance between the target and the substrate is 5 cm. The electrode layer deposition parameters are as follows: RF power is 800 W, deposition pressure is 2 Pa, chamber temperature is 120 ° C, deposition time is 2 h, and the distance between the target and the substrate is 4 cm.)

[0104] (2) The object to be tested and the thin film integrated temperature sensor are transferred to a high-temperature annealing furnace for heat treatment: the annealing furnace temperature rise rate is set to 5°C / min and the maximum temperature is set to 700°C, and the ambient temperature is finally maintained constant at 700°C;

[0105] (3) Measure the change of the crystal structure of the thin film temperature sensor over time;

[0106] (4) Measure the change of ultrasonic signal and sound wave frequency of thin film temperature sensor over time;

[0107] (5) Combining the coating crystal structure, ultrasonic signal, and sound wave frequency changes, it is possible to measure the duration of the object under test at a specific ambient temperature.

[0108] The change of the crystal structure of the thin film temperature sensor over time is as follows Figure 5 (a) It can be seen that as the stainless steel sheet is exposed to the 700℃ environment for a longer time, the crystal structure of the lithium niobate film changes greatly, and the main diffraction peak gradually changes from (012) to (214). The half-height width of the diffraction peak changes as shown in Figure 2. Figure 5 (b) It can be seen that as the time in the high temperature environment increases, the half-height widths of the (012) and (214) diffraction peaks both decrease. Therefore, the duration of the stainless steel sheet working at this temperature can be judged by the peak intensity ratio and the half-height width of the diffraction peaks.

[0109] The change of the ultrasonic signal of the thin film temperature sensor over time is as follows Figure 6 ,Similarly, when the time is less than 168h, the ultrasonic signal is enhanced by prolonging the high temperature time, while when the time is more than 168h, the ultrasonic signal is instantly weakened.

[0110] The frequency of the sound wave of the thin film temperature sensor changes with time. Figure 7 ,As the time the object under test is in the ambient temperature increases, the frequency of the sound wave gradually decreases from 25MHz to 16MHz.

[0111] Therefore, by combining the coating crystal structure, ultrasonic signal, and sound wave frequency changes, it is possible to measure the duration of time that the object under test has been in a specific ambient temperature.

[0112] In combination with Examples 1 to 5, it can be seen that by measuring the changes in the coating surface cross-sectional morphology, grain shape and size, crystal structure, and ultrasonic morphology, the substrate / ambient temperature can be fed back in real time, and the feasibility of measuring the duration of the object to be tested at a specific ambient temperature can be achieved.

[0113] The above is only a preferred specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed in the present application should be covered within the protection scope of the present application.

Claims

1. A lithium niobate thin film temperature sensor, characterized in that: It includes a bonding layer, a piezoelectric coating, a first protective layer, a second protective layer, a transition layer and an electrode layer which are sequentially stacked on a substrate; The electrode layer includes a ground electrode and a surface electrode, and there is a gap of 0.5 mm to 2 mm between the ground electrode and the surface electrode; The piezoelectric coating is a single layer of homogeneous lithium niobate, and the piezoelectric coating is configured to be able to characterize the temperature to be measured through at least one of the surface cross-sectional morphology, grain shape and size, crystal structure, and ultrasonic morphology of the coating; The bonding layer, the lithium niobate piezoelectric coating, the first protective layer, the second protective layer, the transition layer, and the electrode layer are prepared by radio frequency magnetron sputtering; The piezoelectric coating is 10-20 microns thick, and the deposition parameters are as follows: the power of RF magnetron sputtering is 500-1000W, the deposition pressure is 0.5-5Pa, Ar / O2 is 1 / 2-5 / 1, the chamber temperature is 80-250°C, the deposition time is 2h-10h, and the distance between the target and the substrate is 2cm-7cm.

2. The lithium niobate thin film temperature sensor according to claim 1, characterized in that: The bonding layer is Ti or Cr, with a thickness of 50-200 nanometers, and the deposition parameters are as follows: using high-purity Cr or Ti target material, RF power of 500-1000W, deposition pressure of 1-3Pa, argon gas, chamber temperature of 100-300°C, deposition time of 1min-10min, and the distance between the target and the substrate of 3cm-10cm; The first protective layer is SiO2, 2-5 microns thick, and the deposition parameters are as follows: high-purity Si target, RF power of 700-1000W, deposition pressure of 1-3Pa, Ar / O2 of 1 / 2-4 / 1, chamber temperature of 100-300°C, deposition time of 2h-5h, and the distance between the target and the substrate of 3cm-7cm; The second protective layer is Cr, with a thickness of 50-200 nanometers, and the deposition parameters are as follows: using a high-purity Cr target, an RF power of 500-1000W, a deposition pressure of 1-3Pa, pure argon, a chamber temperature of 100-300°C, a deposition time of 1min-10min, and a distance between the target and the substrate of 3cm-10cm; The transition layer is AgCr, with a thickness of 50-200 nanometers, and the deposition parameters are as follows: using a mixed target material of Ag:Cr=1:9~1:1, RF power of 500-1000W, deposition pressure of 1-3Pa, argon, chamber temperature of 100-300°C, deposition time of 1min-10min, and a distance between the target and the substrate of 3cm-10cm; The electrode layer is Ag or Ti or Cr or AgCr, with a thickness of 10-30 microns, and the deposition parameters are as follows: using high-purity Ag or Ti or Cr target or a mixed target of Ag:Cr=1:9~1:1, RF power is 500-1000W, deposition pressure is 0.5-5Pa, pure argon gas, chamber temperature is 80-250°C, deposition time is 2h-10h, and the distance between the target and the substrate is 2cm-7cm.

3. A temperature measurement method, characterized in that: The method is implemented by using the lithium niobate thin film temperature sensor as claimed in claim 1 or 2.

4. The temperature measurement method according to claim 3, characterized in that: The implementation process includes the following steps: (1) Providing the lithium niobate thin film temperature sensor coated on the object to be measured; (2) subjecting the object to be tested and the lithium niobate thin film temperature sensor to heat treatment; (3) measuring at least one of the surface cross-sectional morphology, grain shape and size, crystal structure, and ultrasonic morphology of the piezoelectric coating; (4) The temperature to be measured is obtained based on at least one of the surface cross-sectional morphology, grain shape and size, crystal structure, and ultrasonic morphology.

5. The temperature measurement method according to claim 4, characterized in that: The temperature rise rate of the heat treatment is 2°C / min-5°C / min, and the maximum temperature is 400-1000°C.

6. A temperature measuring device, characterized in that: It comprises a heating area, a thin film temperature sensor, a pulse transmitter-receiver, a controller, and a computer terminal device which are electrically connected in sequence. The thin film temperature sensor is the lithium niobate thin film temperature sensor as claimed in claim 1 or 2.

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