CN116429820A - In-situ monitoring method for phase transition in heat treatment process of zinc oxide piezoresistor - Google Patents
In-situ monitoring method for phase transition in heat treatment process of zinc oxide piezoresistor Download PDFInfo
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- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 title claims abstract description 268
- 238000010438 heat treatment Methods 0.000 title claims abstract description 142
- 238000000034 method Methods 0.000 title claims abstract description 139
- 239000011787 zinc oxide Substances 0.000 title claims abstract description 134
- 230000008569 process Effects 0.000 title claims abstract description 110
- 230000007704 transition Effects 0.000 title claims abstract description 46
- 238000012544 monitoring process Methods 0.000 title claims abstract description 32
- 238000011065 in-situ storage Methods 0.000 title claims abstract description 24
- 239000000919 ceramic Substances 0.000 claims abstract description 93
- 230000004913 activation Effects 0.000 claims abstract description 40
- 238000001816 cooling Methods 0.000 claims abstract description 23
- 238000012360 testing method Methods 0.000 claims description 30
- 230000008859 change Effects 0.000 claims description 19
- 238000000498 ball milling Methods 0.000 claims description 5
- 238000007599 discharging Methods 0.000 claims description 5
- 238000001035 drying Methods 0.000 claims description 5
- 239000003292 glue Substances 0.000 claims description 5
- 238000002156 mixing Methods 0.000 claims description 5
- 101100513612 Microdochium nivale MnCO gene Proteins 0.000 claims description 4
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 4
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical group [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 4
- 239000011248 coating agent Substances 0.000 claims description 3
- 238000000576 coating method Methods 0.000 claims description 3
- 238000009472 formulation Methods 0.000 claims description 3
- 239000000203 mixture Substances 0.000 claims description 3
- 229910052697 platinum Inorganic materials 0.000 claims description 2
- 229910052709 silver Inorganic materials 0.000 claims description 2
- 239000004332 silver Substances 0.000 claims description 2
- 239000000463 material Substances 0.000 claims 1
- 239000002994 raw material Substances 0.000 claims 1
- 238000004321 preservation Methods 0.000 description 18
- 230000000630 rising effect Effects 0.000 description 7
- 238000005245 sintering Methods 0.000 description 6
- 229910015902 Bi 2 O 3 Inorganic materials 0.000 description 4
- 230000009467 reduction Effects 0.000 description 4
- 238000002360 preparation method Methods 0.000 description 3
- 238000001237 Raman spectrum Methods 0.000 description 2
- 238000001453 impedance spectrum Methods 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 238000007711 solidification Methods 0.000 description 2
- 230000008023 solidification Effects 0.000 description 2
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000011162 core material Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
- G01N25/02—Investigating or analyzing materials by the use of thermal means by investigating changes of state or changes of phase; by investigating sintering
- G01N25/12—Investigating or analyzing materials by the use of thermal means by investigating changes of state or changes of phase; by investigating sintering of critical point; of other phase change
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/041—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance
- G01N27/221—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance by investigating the dielectric properties
Abstract
The application belongs to the technical field of zinc oxide ceramic resistors, and particularly relates to an in-situ monitoring method for phase transition in a zinc oxide piezoresistor heat treatment process, wherein the in-situ monitoring method provided by the application solves the problem that Bi in the zinc oxide piezoresistor heat treatment process is lacking in the prior art by acquiring the DC conductivity activation energy of a heating stage or the dielectric constant of a cooling stage in the zinc oxide piezoresistor blank heat treatment process 2 O 3 The technical problem of an in-situ monitoring method of phase transition.
Description
Technical Field
The application belongs to the technical field of zinc oxide ceramic resistors, and particularly relates to an in-situ monitoring method for phase transition in a heat treatment process of a zinc oxide piezoresistor.
Background
The zinc oxide pressure sensitive ceramic (ZnO varistor ceramic) has excellent nonlinear voltage-current characteristics, is commonly used for overvoltage protection of power systems and electrical equipment, and is a core material of a metal oxide arrester.
The heat treatment is an important process for optimizing the performance of the zinc oxide pressure-sensitive ceramic, and the component Bi of the zinc oxide pressure-sensitive ceramic in the heat treatment process 2 O 3 Phase transition occurs, bi 2 O 3 The influence of the phase transformation process on the transmission of grain boundary oxygen is the main reason for the change of the performance of the zinc oxide pressure-sensitive ceramic, therefore, bi 2 O 3 The phase transition process has received much attention from many scholars, however, currently Bi is typically monitored by comparing the Raman spectra of zinc oxide pressure sensitive ceramics before and after heat treatment 2 O 3 Phase transition process, lack of Bi during heat treatment 2 O 3 In-situ monitoring means of phase change process, for Bi in heat treatment process 2 O 3 The phase change process is not well known, and is not beneficial to optimizing the preparation process of the zinc oxide pressure-sensitive ceramic.
Disclosure of Invention
The application provides an in-situ monitoring method for phase transition in the heat treatment process of a zinc oxide piezoresistor, which is used for solving the problem that Bi is lacking in the prior art in the heat treatment process of the zinc oxide piezoresistor 2 O 3 The technical problem of an in-situ monitoring method of phase transition.
The first aspect of the application provides an in-situ monitoring method for phase transition in a heat treatment process of a zinc oxide varistor, which comprises the following steps:
step S1, placing a zinc oxide pressure-sensitive ceramic resistor blank in a testing instrument for heat treatment to obtain the temperature and the direct current conductivity of a heating stage in the heat treatment process of the zinc oxide pressure-sensitive ceramic resistor blank;
s2, obtaining direct current conductivity activation energy of the heating stage in the heat treatment process of the zinc oxide pressure sensitive ceramic resistor blank according to the temperature and the direct current conductivity of the heating stage in the heat treatment process of the zinc oxide pressure sensitive ceramic resistor blank;
step S3, according to the temperature rising step in the heat treatment process of the zinc oxide pressure sensitive ceramic resistor blankBi in the heating stage in the heat treatment process of zinc oxide pressure sensitive ceramic resistor blank body is monitored by direct current conduction activation energy of the section 2 O 3 And (3) a phase change process.
Preferably, the in-situ monitoring method for phase transition in the heat treatment process of the zinc oxide piezoresistor further comprises the following steps:
s4, placing the zinc oxide pressure-sensitive ceramic resistor blank in a testing instrument for heat treatment to obtain the dielectric constant of the cooling stage in the heat treatment process of the zinc oxide pressure-sensitive ceramic resistor blank;
s5, obtaining Bi at a cooling stage in the heat treatment process of the zinc oxide ceramic resistor blank according to the dielectric constant in the heat treatment process of the zinc oxide ceramic resistor blank 2 O 3 And (3) a phase change process.
Preferably, in step S1 and step S4, the test instrument is a high-temperature high-pressure broadband dielectric spectrometer;
the test frequency of the high-temperature high-pressure broadband dielectric spectrometer is 1 Hz-10 6 Hz, test AC small signal 1V.
Preferably, the dielectric constant in the heat treatment process is the dielectric constant in the heating stage, the heat preservation stage and the cooling stage in the heat treatment process.
Preferably, the temperature of the heat preservation stage in the heat treatment process is 400-800 ℃.
Preferably, the temperature of the heat preservation stage in the heat treatment process is 550-800 ℃;
preferably, the heating rate range of the heating stage in the heat treatment process is 2-10 ℃/min;
the time range of the heat preservation stage in the heat treatment process is 1-12 h;
the cooling stage in the heat treatment process is furnace-following cooling.
It should be noted that, the high-temperature high-pressure broadband dielectric spectrometer is equipped with a high-temperature furnace test cavity, the model is Novocontrol Concept, germany, and the furnace cooling refers to closing the heat preservation procedure of the high-temperature high-pressure broadband dielectric spectrometer for cooling.
Preferably, step S2, according to the temperature and the dc conductivity of the heating stage in the heat treatment process of the zinc oxide pressure sensitive ceramic resistor blank, the obtaining the dc conductivity activation energy of the heating stage in the heat treatment process of the zinc oxide pressure sensitive ceramic resistor blank specifically includes: calculating to obtain direct current conductivity activation energy according to a direct current conductivity activation energy formula;
the formula of the direct current conductivity activation energy is as follows:
in the formula (1), E a Is direct current conductance activation energy/eV, K is Boltzmann constant, T is temperature/K, sigma 0 Is direct current conductivity/S.m -1 ，σ dc Is the direct current conductivity/S.m -1 。
Preferably, in step S2, according to the temperature and the dc conductivity of the heating stage in the heat treatment process of the zinc oxide pressure sensitive ceramic resistor blank, obtaining the dc conductivity activation energy of the heating stage in the heat treatment process of the zinc oxide pressure sensitive ceramic resistor blank specifically includes: calculating to obtain direct current conductivity activation energy according to a direct current conductivity activation energy formula;
the formula of the direct current conductivity activation energy is as follows:
in the formula (2), E a Is direct current conductance activation energy/eV, K is Boltzmann constant, T is temperature/K, sigma 0 Is direct current conductivity/S.m -1 ，σ dc Is the direct current conductivity/S.m -1 。
Preferably, in step S1, the method for preparing the zinc oxide voltage-sensitive ceramic resistor blank comprises
Step S21, sequentially carrying out mixing, ball milling, drying, granulating, tabletting and glue discharging on a zinc oxide ceramic formula to prepare a zinc oxide ceramic green body;
and S22, coating high-temperature resistant conductive paste on the surfaces of two end surfaces of the zinc oxide ceramic green body, and curing the high-temperature resistant conductive paste at high temperature to obtain a zinc oxide pressure-sensitive ceramic resistor green body.
Preferably, in step S21, the zinc oxide pressure sensitive ceramic formulation comprises 93.42mol parts of ZnO and 1.2mol parts of Bi in terms of mass parts 2 O 3 1 molar part of Sb 2 O 3 1.1 molar parts of Co 2 O 3 0.5 molar part of MnCO 3 1.3 molar parts of Ni 2 O 3 1.48 mol parts of SiO 2 。
Preferably, in step S22, the high temperature resistant conductive paste is silver paste or platinum paste;
preferably, in step S22, the high-temperature curing temperature is 500 ℃, and the curing time is 30min.
In summary, the application provides an in-situ monitoring method for phase transition in a zinc oxide piezoresistor heat treatment process, the monitoring method comprises the steps of performing heat treatment on a zinc oxide pressure-sensitive ceramic resistor blank through a testing instrument such as a high-temperature high-pressure broadband dielectric spectrometer and the like to obtain the temperature and direct current conductivity of a heating stage in the zinc oxide pressure-sensitive ceramic resistor blank heat treatment process, and drawing sigma according to a formula dc 1/T curve, fitting to calculate DC conductivity activation energy, and calculating the activation energy only by DC conductivity at different temperatures, wherein the DC conductivity can also pass through sigma dc Obtained by a 1/T curve, bi in the heat treatment process of the zinc oxide pressure-sensitive ceramic resistor blank is monitored according to the direct current conductivity activation energy 2 O 3 A phase change process; or the zinc oxide pressure-sensitive ceramic resistor blank is subjected to heat treatment by a testing instrument such as a high-temperature high-pressure broadband dielectric spectrometer, so as to obtain the dielectric constant of the zinc oxide pressure-sensitive ceramic resistor blank in the cooling stage in the heat treatment process, and Bi in the heat treatment process of the zinc oxide pressure-sensitive ceramic resistor blank is monitored according to the dielectric constant 2 O 3 In the phase change process, the direct current conductivity activation energy and the dielectric constant obtained by a testing instrument can be used for monitoring Bi in the process of heat treatment of zinc oxide pressure-sensitive ceramic resistor 2 O 3 The phase change process solves the problem of Bi in the heat treatment process of zinc oxide piezoresistor lacking in the prior art 2 O 3 The technical problem of an in-situ monitoring method of phase transition.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram showing the change of the electrical conductivity and activation energy of zinc oxide pressure sensitive ceramic in the heat treatment process of experimental example 1 of the application;
FIG. 2 is a graph showing the change of dielectric constant of zinc oxide pressure sensitive ceramic resistor during heat treatment in experimental example 1 of the present application;
FIG. 3 is a Raman spectrum chart of the zinc oxide pressure sensitive ceramic resistor at the heating stage in the heat treatment process of experimental example 1 of the application;
FIG. 4 is an X-ray derivative graph of zinc oxide pressure sensitive ceramic resistor at the cooling stage in the heat treatment process of experimental example 1 of the application.
Detailed Description
The application provides an in-situ monitoring method for phase transition in the heat treatment process of a zinc oxide piezoresistor, which is used for solving the problem that Bi is lacking in the prior art in the heat treatment process of the zinc oxide piezoresistor 2 O 3 The technical problem of an in-situ monitoring method of phase transition.
The following description of the embodiments of the present application will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.
Example 1
In view of the lack of Bi in the heat treatment process of the zinc oxide piezoresistor in the prior art 2 O 3 Direct monitoring of the phase transition is not possible to obtain Bi during the heat treatment 2 O 3 The temperature of phase transition is unfavorable for optimizing the preparation process of the zinc oxide varistor, and the embodiment 1 of the application provides an oxidationThe in-situ monitoring method for the phase state transition in the heat treatment process of the zinc piezoresistor comprises the following steps: the method comprises the steps of preparing a zinc oxide pressure-sensitive ceramic resistor blank, heat treating the zinc oxide ceramic resistor blank, obtaining direct current conduction activation energy of a heating stage in the heat treatment process of the zinc oxide pressure-sensitive ceramic resistor blank or obtaining dielectric constants of the heating stage, the heat preservation stage and the cooling stage in the heat treatment process of the zinc oxide pressure-sensitive ceramic resistor blank.
The preparation method comprises the steps of sequentially mixing, ball milling, drying, granulating, tabletting and discharging glue of a zinc oxide ceramic formula to obtain a zinc oxide ceramic green body, coating high-temperature resistant conductive paste on the surfaces of two end surfaces of the zinc oxide ceramic green body, and curing the high-temperature resistant conductive paste at high temperature to obtain the zinc oxide ceramic green body; wherein the zinc oxide pressure sensitive ceramic formula comprises 93.42mol parts of ZnO and 1.2mol parts of Bi 2 O 3 1 molar part of Sb 2 O 3 1.1 molar parts of Co 2 O 3 0.5 molar part of MnCO 3 1.3 molar parts of Ni 2 O 3 1.48 mol parts of SiO 2 。
The step of heat treating the zinc oxide pressure sensitive ceramic resistor blank comprises the following steps: placing the sample into a sintering furnace and connecting a testing system for heat treatment, wherein the heating rate of a heating stage of the heat treatment is 2-10 ℃/min, the temperature of a heat preservation stage is 750 ℃, the heat preservation time is 1-12 h, and the sample is sintered at high temperature and simultaneously tested for conductivity characteristics to obtain the temperature of the heating stage and the cooling stage and the direct current conductivity in the sintering process of the zinc oxide piezoresistor; wherein the test system is specifically a high-temperature high-pressure broadband dielectric spectrometer, novocontrol Concept43, germany, and the test condition of the high-temperature high-pressure broadband dielectric spectrometer is that the test frequency is 1 Hz-10 6 Hz, test AC small signal 1V.
The step of obtaining the direct current conduction activation energy of the heating stage in the zinc oxide pressure sensitive ceramic resistor blank heat treatment process comprises the following steps: obtaining the direct current conductivity activation energy of the heating stage in the heat treatment process of the zinc oxide pressure sensitive ceramic resistor blank according to the temperature and the direct current conductivity of the heating stage in the heat treatment process of the zinc oxide pressure sensitive ceramic resistor blank;
wherein, the formula of the direct current conductivity activation energy is:
in the formulae (1) to (2), E a Is direct current conductivity activation energy/eV, K is Boltzmann constant, T is Kelvin temperature/K, sigma 0 Is direct current conductivity/S.m -1 ，σ dc Is the direct current conductivity/S.m -1 The formula calculation process is to draw the logarithm of the direct current conductivities of different temperatures and the reciprocal curve sigma of the corresponding temperatures dc 1/T, and fitting to obtain slope-E of curve a And/k, further calculating the direct current conductivity activation energy E at different temperatures in the temperature rising stage in the sintering process a Is of a size of (a) and (b).
Bi during the heat treatment of the zinc oxide pressure sensitive ceramic resistor blank 2 O 3 The phase transition can change the conduction mechanism from original electron-dominated conduction to oxygen ion conduction, resulting in the change of the direct current conduction activation energy, so that the application can obtain the direct current conduction activation energy E at different temperatures in the heating stage in the heat treatment process a The size change of the zinc oxide voltage-sensitive ceramic resistor can effectively monitor Bi in the sintering process of the zinc oxide voltage-sensitive ceramic resistor 2 O 3 The phase state transition process is used for obtaining the zinc oxide pressure sensitive ceramic resistor Bi in the sintering process 2 O 3 The temperature at which the phase transition occurs, thereby solving the technical problem that the monitoring means in the zinc oxide ceramic resistor sintering process is lacked in the prior art.
Meanwhile, embodiment 1 of the present application further provides a step of obtaining a dielectric constant at a cooling stage in a heat treatment process of the zinc oxide pressure sensitive ceramic resistor blank, where the step includes: placing the zinc oxide pressure-sensitive ceramic resistor blank in a testing instrument for heat treatment to obtain the dielectric constant of the zinc oxide pressure-sensitive ceramic resistor blank in the heat treatment process; wherein the heating rate of the heat treatment is 2-10 ℃/min, the temperature of the heat preservation stage is 550 ℃,600 ℃, 650 ℃,700 ℃, 750 ℃ and the heat preservation time is 1-12 h, wherein the test instrument is a high-temperature high-pressure broadband dielectric spectrometer, novocontrol concept, germany, the test condition of the high-temperature high-pressure broadband dielectric spectrometer is 100Hz, and the test alternating current small signal is 1V.
In the heat treatment process of the zinc oxide pressure-sensitive ceramic resistor blank, the dielectric constant of the zinc oxide pressure-sensitive ceramic resistor blank at the same frequency (for example, 100 Hz) is gradually increased during heat preservation, and when the temperature begins to be reduced and suddenly changes, the internal phase change is indicated to be started, and the alpha phase is converted into the beta phase or the gamma phase, so that the dielectric constant is changed.
Experimental example 1
Commercial formulation of typical zinc oxide pressure sensitive ceramic resistor 93.42mol% ZnO,1.2mol% Bi 2 O 3 ,1mol％Sb 2 O 3 ，1.1mol％Co 2 O 3 ，0.5mol％MnCO 3 ，1.3mol％Ni 2 O 3 ，1.48mol％SiO 2 For example, experimental example 1 of the application provides monitoring of the temperature rising stage of the heat treatment process of the zinc oxide piezoresistor, and obtaining the zinc oxide piezoceramic resistor Bi for obtaining the temperature rising stage of the heat treatment process according to the electric conduction activation energy 2 O 3 The temperature at which the phase transition occurs;
the monitoring of the temperature rising stage, the heat preservation stage and the temperature reduction stage of the zinc oxide piezoresistor heat treatment process at the same frequency is also provided, and the zinc oxide piezoceramic resistor Bi used for obtaining the temperature rising stage in the heat treatment process according to the dielectric constant 2 O 3 The temperature at which the phase transition occurs.
Experimental example 1.1 obtaining a Zinc oxide pressure-sensitive ceramic resistor Bi for obtaining a temperature-rising stage in a Heat treatment Process according to conductivity activation energy 2 O 3 The temperature experimental process of the phase transition is as follows: the commercial formula of the typical zinc oxide voltage-sensitive ceramic resistor is subjected to batching, mixing, ball milling, drying, granulating, tabletting and glue discharging to obtain a batch of 5 zinc oxide voltage-sensitive resistor green body samples, and the two ends of the prepared zinc oxide voltage-sensitive resistor green body samples are coated with high-temperature conductive silver paste and then are placed in 500And (3) maintaining the temperature for 30min in the environment at the temperature to solidify the electrode. After solidification, cooling the sample to room temperature, placing the sample in a high-temperature furnace chamber test module of a dielectric spectrum, and performing a heat treatment process at 750 ℃, wherein the test conditions are set to be 3.33 ℃/min in heating rate, 2h in heat preservation time and 1V in test alternating current small signal amplitude.
As shown in FIG. 1, it is clear from FIG. 1 that the DC conduction activation energy remains almost unchanged in the temperature range of 300 to 400 ℃, gradually increases in the temperature range of 400 to 600 ℃, and has an abnormally high value in the temperature range of 600 to 700 ℃, which means that at 400 to 600 ℃, the alpha-Bi is obtained 2 O 3 Phase transition to beta-Bi 2 O 3 Phase, causing a transition of the conductivity mechanism, which indicates that the zinc oxide pressure-sensitive ceramic resistance Bi during heat treatment can be obtained based on the conductivity activation energy 2 O 3 The phase transition occurs at a temperature of about 400 to 600 c.
To further verify that the zinc oxide voltage-sensitive ceramic resistor Bi used for obtaining the heating stage in the heat treatment process is obtained according to the electric conduction activation energy 2 O 3 The temperature reliability of the phase transition is also shown in the experimental example 1, the phase transition of the zinc oxide piezoresistor sample in the whole heat treatment temperature rising process is monitored through a high Wen Laman spectrum (model Renishaw inVia Qontor), the experimental process is the same as that of the experimental example 1.1, the experimental result is shown in fig. 3, and the zinc oxide pressure sensitive ceramic is Bi at the normal temperature of 25 DEG C 2 O 3 The phase state of the sample is alpha phase, the phase state of the sample starts to change along with the rise of the temperature, and when the temperature reaches 600 ℃, bi 2 O 3 The phase of (c) is converted to the beta phase. Further temperature rise, bi 2 O 3 The phase state of (a) remains as beta phase all the time, which is equivalent to monitoring Bi based on DC conduction activation energy 2 O 3 The temperature results of the phase transition are consistent, which shows that the zinc oxide voltage-sensitive ceramic resistor Bi obtained according to the conductivity activation energy and used for obtaining the heating stage in the heat treatment process 2 O 3 Reliability of the temperature at which the phase transition occurs.
Experimental example 1.2 use of the dielectric constant for obtaining Zinc oxide pressure sensitive ceramic resistor Bi at the Cooling stage in the Heat treatment Process 2 O 3 The temperature experimental process of the phase transition is as follows: the commercial formula of the typical zinc oxide voltage-sensitive ceramic resistor is subjected to batching, mixing, ball milling, drying, granulating, tabletting and glue discharging to obtain a batch of 5 zinc oxide voltage-sensitive resistor green body samples, and the two ends of the prepared zinc oxide voltage-sensitive resistor green body samples are coated with high-temperature conductive silver paste and then are placed in a 500 ℃ environment for 30min to solidify the electrodes. After solidification, cooling the sample to room temperature, placing the sample in a high-temperature furnace chamber test module of a dielectric spectrum, and performing a heat treatment process at 550 ℃,600 ℃, 650 ℃,700 ℃ and 750 ℃ under the test conditions of 3.33 ℃/min of heating rate, 2h of heat preservation time and 1V of test alternating current small signal amplitude.
As shown in FIG. 2, the dielectric constant hardly changes below 400 ℃ as the temperature increases further, the dielectric constant begins to increase rapidly until the temperature increases to the heat treatment temperature for heat preservation, the dielectric constant gradually increases during the heat preservation, and the increase of the dielectric constant becomes more and more obvious along with the increase of the temperature, which indicates that Bi still continuously occurs during the heat preservation 2 O 3 In the phase change process of (2), the dielectric constant continuously decreases in the cooling process, the zinc oxide pressure sensitive ceramic resistor blank gradually increases in the heat preservation process, and when the temperature begins to be suddenly changed, the internal phase change is indicated to be started, the alpha phase is converted into the beta phase or the gamma phase, and the dielectric constant is changed, which indicates that the zinc oxide pressure sensitive ceramic resistor Bi in the heat treatment process can be obtained based on the dielectric constant 2 O 3 The phase transition stage comprises a cooling stage, and further the zinc oxide voltage-sensitive ceramic resistor Bi used for obtaining the cooling stage in the heat treatment process is obtained according to the dielectric constant 2 O 3 The temperature reliability of the phase transition is shown in fig. 4, the experimental example 1 also carries out the X-ray diffractometer (model Bruke D8 advanced) to test the phase structure of the zinc oxide after the temperature reduction, the experimental process is shown in the experimental example 1.2, the experimental result is shown in fig. 4, the temperature reduction is carried out after the heat treatment at 700 ℃ and 750 ℃ and the Bi is shown in fig. 4 2 O 3 The phase state comprises gamma-phase Bi 2 O 3 This shows that based on the dielectric constant, the zinc oxide pressure-sensitive ceramic resistance Bi during heat treatment can be obtained 2 O 3 The phase transition occurs at a stage including a temperature reduction stage, and Bi can be determined in conjunction with FIG. 2 2 O 3 The phase transition occurs at a temperature of about 600 to 650 ℃, which is comparable to that at which, based on the dielectric constant, a zinc oxide voltage-sensitive ceramic resistor Bi can be obtained for the cooling phase during the heat treatment 2 O 3 The temperature bureau reliability at which the phase transition occurs.
The above embodiments are only for illustrating the technical solution of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.
Claims (9)
1. The in-situ monitoring method for the phase transition in the heat treatment process of the zinc oxide piezoresistor is characterized by comprising the following steps:
step S1, placing a zinc oxide pressure-sensitive ceramic resistor blank in a testing instrument for heat treatment to obtain the temperature and the direct current conductivity of a heating stage in the heat treatment process of the zinc oxide pressure-sensitive ceramic resistor blank;
s2, obtaining direct current conductivity activation energy of the heating stage in the heat treatment process of the zinc oxide pressure sensitive ceramic resistor blank according to the temperature and the direct current conductivity of the heating stage in the heat treatment process of the zinc oxide pressure sensitive ceramic resistor blank;
s3, monitoring Bi at the heating stage in the heat treatment process of the zinc oxide pressure-sensitive ceramic resistor blank according to the direct current conduction activation energy at the heating stage in the heat treatment process of the zinc oxide pressure-sensitive ceramic resistor blank 2 O 3 And (3) a phase change process.
2. The method for in-situ monitoring of phase transitions during heat treatment of a zinc oxide varistor of claim 1, further comprising the steps of:
s4, placing the zinc oxide pressure-sensitive ceramic resistor blank in a testing instrument for heat treatment to obtain the dielectric constant of the cooling stage in the heat treatment process of the zinc oxide pressure-sensitive ceramic resistor blank;
s5, obtaining Bi at the cooling stage in the heat treatment process of the zinc oxide ceramic resistor blank according to the dielectric constant at the cooling stage in the heat treatment process of the zinc oxide ceramic resistor blank 2 O 3 And (3) a phase change process.
3. The method for in-situ monitoring of phase transition in a heat treatment process of a zinc oxide varistor according to claim 1 or 2, wherein in step S1 and step S4, the test instrument is a high-temperature high-pressure broadband dielectric spectrometer;
the test frequency of the high-temperature high-pressure broadband dielectric spectrometer is 1 Hz-10 6 Hz, test AC small signal 1V.
4. The method for in-situ monitoring of phase transition in a heat treatment process of a zinc oxide varistor according to claim 1 or 2, wherein in step S1 and step S4, the temperature of the heat-preserving stage in the heat treatment process is 400-800 ℃.
5. The method for in-situ monitoring of phase transition in a heat treatment process of a zinc oxide varistor according to claim 1, wherein the step S2 of obtaining the dc conductivity activation energy of the heating stage in the heat treatment process of the zinc oxide varistor green body according to the temperature and the dc conductivity of the heating stage in the heat treatment process of the zinc oxide varistor green body specifically comprises: calculating to obtain direct current conductivity activation energy according to a direct current conductivity activation energy formula;
the formula of the direct current conductivity activation energy is as follows:
in the formula (1), E a Is direct current conductivity activation energy/eV, K is Boltzmann constant, T is Kelvin temperature/K, sigma 0 Is direct currentconductivity/S.m -1 ，σ dc Is the direct current conductivity/S.m -1 。
6. The method for in-situ monitoring of phase transition in a heat treatment process of a zinc oxide varistor according to claim 1, wherein in step S1, the method for preparing a zinc oxide varistor ceramic resistor blank comprises the steps of:
step S11, sequentially carrying out material mixing, ball milling, drying, granulating, tabletting and glue discharging on raw materials of the zinc oxide ceramic formula to prepare a zinc oxide ceramic green body;
and S12, coating high-temperature resistant conductive paste on the surfaces of two end surfaces of the zinc oxide ceramic green body, and curing the high-temperature resistant conductive paste at high temperature to obtain a zinc oxide pressure-sensitive ceramic resistor green body.
7. The method for in-situ monitoring of phase transition during heat treatment of zinc oxide varistor according to claim 1, wherein in step S21, the zinc oxide pressure sensitive ceramic formulation comprises 93.42mol parts of ZnO and 1.2mol parts of Bi in terms of mass parts 2 O 3 1 molar part of Sb 2 O 3 1.1 molar parts of Co 2 O 3 0.5 molar part of MnCO 3 1.3 molar parts of Ni 2 O 3 1.48 mol parts of SiO 2 。
8. The method according to claim 1, wherein in step S22, the high temperature resistant conductive paste is silver paste or platinum paste.
9. The method for in-situ monitoring of phase transition during heat treatment of zinc oxide varistor according to claim 1, wherein in step S22, the high-temperature curing temperature is 500 ℃; the time was 30min.
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