CN113390900A - Microwave technology-based device and method for detecting substance metallization transition under high pressure - Google Patents
Microwave technology-based device and method for detecting substance metallization transition under high pressure Download PDFInfo
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Abstract
The invention relates to a device and a method for detecting material metallization transition under high pressure based on microwave technology, wherein the detection device consists of a microwave generator, a microwave transmission line, a DAC (digital-to-analog converter) detection unit and a parameter detection device, the DAC detection unit is provided with an input end and an output end, the microwave generator is connected with the input end of the DAC detection unit through the microwave transmission line, microwave signals are input into a resonant cavity and transmitted to generate back-and-forth reflection, and when the wavelength is matched with the size of the resonant cavity, resonance occurs; the parameter detection device is connected with the output end through a microwave transmission line. The invention combines the microwave resonant cavity and the diamond anvil cell for detecting the metallization transition process of the substance under high pressure, thereby improving the anti-interference capability of the device; the probe electrode is not required to be in direct contact with a measured object during detection, the power of the used microwave is low, the generated radiation is very little, no pollution is generated, the gasket and the sample are convenient to replace, the universality is high, and the method is widely applied to high-voltage scientific substance metallization transition research.
Description
Technical Field
The invention belongs to the technical field of high-pressure material metallization transition detection, and particularly relates to a detection device and a detection method for researching material metallization transition under high pressure based on a microwave resonance technology.
Background
The high-pressure physics is a subject for researching physical behaviors of substances under the action of extreme pressure, and the structures and properties of the substances can be obtained under the high pressure, so that the high-pressure physics has important promotion effects on other subjects, such as geoscience, condensed state physics, chemistry, material science, biological science and the like. The metal-to-metal transition is a phenomenon that a substance is changed from a non-metal state to a metal state, and the change generally corresponds to a structural phase change, so that the physical properties of the material are changed. In 1925, bernas ear, british physicist: any material may become metallic under sufficient pressure, a characteristic phase change resulting from high pressure. The recent development of high-pressure physics proves its correctness, and the corresponding phase-change pressure is called metallization pressure. Conversely, the phenomenon of metallic state to non-metallic state, which is the reverse of metallic transition, can also be referred to as non-metallic transition.
There are many techniques for detecting the metal transition of a substance through high voltage experiments, such as sound waves, magnetic fields, electric properties, X-rays, gamma rays, etc., and among them, the detection by an electric method is the most direct and effective means. The high-voltage electrical detection method mainly utilizes the combination of a Diamond Anvil Cell (DAC) and a four-probe method to disclose the structural characteristics and the conduction mechanism of phase change of substances under high pressure.
The research on the high-voltage electricity and structural phase change of iron discloses that a four-column DAC device is adopted, metal leads are arranged on a DAC anvil surface, a magnetron sputtering method and a photoetching method are used, four-point electrodes are integrated on the DAC anvil surface, the high-voltage electricity research of 75-micrometer thin iron wires is carried out, the pressure is calibrated by adopting a ruby fluorescence technology, and the result shows that the phase change of a sample occurs at 14.3GPa, the resistance obviously changes, alpha-phase iron in the sample is completely converted into epsilon phase, the crystal structure changes under high pressure, and the electrical property changes. However, the application of the four-probe method has limitations in that four electrodes need to be engraved on diamond, requiring the electrodes to be in contact with the sample, limiting ultra-high pressure application.
The rapid development of microwave technology over decades has become an application technology research hotspot, which is a subject of research on the generation, amplification, transmission, emission, reception and measurement of microwave signals. The frequency of the microwave is high, so that the actual usable frequency band is wide under a certain relative bandwidth. The microwave frequency band is wide, and the transmission rate is high. However, microwaves are currently used in a few fields of high-pressure science. CN109580662A utilizes microwave technology to detect metal structure phase change high pressure in-situ measurement device and measurement method, utilizes spiral antenna to detect microwave reflected power and transmitted power, then carries out arithmetic processing to obtain the metal structure phase change degree of the sample to be measured, and confirms the metal structure high pressure phase change point of the sample to be measured with this. However, the test space of this method is in the DAC, and the metal member is around it, so the test is easily interfered by the electromagnetic interference of the environment, and the spiral antenna is not easy to be manufactured.
The invention improves the limitation of the traditional high-voltage electrical detection technical method, combines the microwave resonant cavity with the DAC, avoids external electromagnetic interference and improves the anti-interference capability of the device. The microwave method belongs to non-contact measurement. Meanwhile, the invention also has the characteristics of no pollution, strong universality, quickness and the like.
Disclosure of Invention
The invention aims to provide a device for detecting the material metallization transition under high pressure based on a microwave technology and a method for detecting the material metallization transition under high pressure based on the microwave technology, so as to solve the problem that the traditional method for detecting the electricity under high pressure is limited, and the material metallization transition is detected under high pressure by combining a microwave resonant cavity and a diamond anvil pair.
The purpose of the invention is realized by the following technical scheme:
a device for detecting substance metallization conversion under high pressure based on microwave technology is composed of a microwave generator 1, a microwave transmission line 2, a DAC detection unit 3 and a parameter detection device 4;
the DAC detection unit 3 comprises a resonant cavity 9, an upper diamond anvil 8 arranged in the resonant cavity 9, a gasket 11, a sample cavity 12 for containing a sample 13 doped with ruby powder and a pressure transmission medium, a lower diamond anvil 14, a lower support block 15, an input end 17, an output end 18 and an observation window 19 arranged on the lower support block 15; the upper diamond anvil cell 8 and the lower diamond anvil cell 14 are symmetrically arranged at the upper side and the lower side of the sample cavity 12; the input end 17 and the output end 18 are arranged on an upper support block 6 forming the resonant cavity 9, the bottoms of the upper support block and the lower support block extend into the resonant cavity 9, and the upper support block 6 and the lower support block 15 are fastened through 4 bolts 5;
the microwave generator 1 is connected with the input end 17 through a microwave transmission line 2, microwave signals are input into the resonant cavity 9 and transmitted to be reflected back and forth, and when the wavelength is matched with the size of the resonant cavity 9, resonance occurs; the parameter detection device 4 is connected with the output end 18 through the microwave transmission line 2, and the microwave signal is led out to the parameter detection device 4.
Furthermore, the resonant cavity 9 is a rectangular resonant cavity or a circular resonant cavity, and is surrounded by the upper supporting block 6, the resonant cavity wall 7 and the gasket 11, the upper supporting block 6 and the resonant cavity wall 7 are integrally formed, and the gasket 11 is arranged below the resonant cavity wall 7, is in close contact with the resonant cavity wall 7, and is adhered together through the conductive silver adhesive 10.
Further, the sample chamber 12 is provided in the pad 11.
Further, the upper diamond anvil 8 is at the same height as the resonator wall 7.
Further, the microwave generator 1 is a Voltage Controlled Oscillator (VCO), a broadband microwave source or a vector network analyzer; when the resonant cavity 9 is a rectangular resonant cavity, the microwave transmission line 2 uses a waveguide transmission line or a coaxial transmission line, and when the resonant cavity 9 is a circular resonant cavity, the microwave transmission line 2 uses a coaxial transmission line; the input end 17 is an SMA adapter or a waveguide adapter in the rectangular resonant cavity, and is an SMA adapter in the circular resonant cavity; the parameter detection device 4 is a frequency meter, a power meter or a vector network analyzer.
Furthermore, when the resonant cavity 9 is rectangular, the hole is located 0mm to 3.5mm away from the center point X, and the hole diameter is 100 μm to 1000 μm, which is the same as the diamond anvil surface; when the diamond anvil surface is round, the hole is positioned at the position 0 mm-2.5 mm away from the central point X, the hole diameter is 100 mu m-1000 mu m, and the hole diameter is the same as the diamond anvil surface; the rectangular resonant cavity 9 and the circular resonant cavity 9 have the same height, which is 2 mm-3 mm.
A method for detecting substance metallization transition under high pressure based on microwave technology comprises the following steps:
A. the microwave generator 1 and the parameter detection device 4 are respectively connected with an input end 17 and an output end 18 through a microwave transmission line 2;
B. the pad 11 is placed on the lower diamond anvil 14 (aligned by the transparent viewing window 19);
C. firstly picking a small amount of sample 13 powder out, placing the sample on the anvil surface of a lower diamond anvil cell 14, picking a small amount of sample with a needle tip to fill a sample cavity 12 as much as possible, and then uniformly placing the ruby powder on the sample 13 for prepressing;
D. the upper diamond anvil cell 8 and the resonant cavity wall 7 are the same in height, so that the resonant cavity wall 7 can be in close contact with the gasket 11, and the resonant cavity wall 7 is bonded with the gasket 11 through the silver adhesive 10, so that the tightness of the resonant cavity 9 is ensured;
E. and based on the selected types of the microwave generator 1 and the parameter detection device 4, judging the high-voltage phase change point of the substance metallization transformation by measuring the quality factor Q, S parameter, the resonance frequency f and the impedance Z.
Further, step E, based on the selected types of the microwave generator 1 and the parameter detection device 4, determining the material metallization transition high-voltage phase transition point by measuring the quality factor Q, S parameter, the resonant frequency f and the impedance Z, specifically comprising the following steps:
the microwave generator 1 inputs microwave signals into the resonant cavity 9 through the input port 17 by using the microwave transmission line 2, the microwave signals are reflected back and forth in the resonant cavity 9, and when the wavelength is matched with the size of the resonant cavity 9, the microwave signals accord with the relational expressions of the formula (1), the formula (2) or the formula (3) and the formula (4), and resonance occurs;
when the size of the resonant cavity 9 is designed, the size of the resonant cavity 9 is preliminarily calculated through a formula (1), a formula (2), a formula (3) and a formula (4), and the optimal resonant cavity specification is obtained through combination of HFSS simulation and experiments;
if the length and width of the rectangular resonant cavity 9 are both 6 mm-15 mm and the height is 2mm, there are many working modes of the rectangular resonant cavity 9 in this range, taking the TE101 mode of the working mode of the rectangular resonant cavity 9 as an example, the resonant frequency f and the quality factor Q are respectively:
where a is the width of the rectangle, b is the height of the rectangle, l is the length of the rectangle, c is the speed of light, μ is the permeability, and σ is the conductivity. Wherein Q is a quality factor, and may be Q when the sample 13 is a non-metal when not pressurized0When the sample 13 is a metal under pressure, Q may be usedL. f is the resonance frequency, and may be f when the sample 13 is not metallic when not pressurizedNon-metalOr f in the case where sample 13 is a metal under pressureMetal；
If the radius range of the cylindrical resonant cavity 9 is 4 mm-12 mm and the height is 2mm, there are many working modes of the cylindrical resonant cavity 9 in this range, taking the working mode TM010 mode of the cylindrical resonant cavity 9 as an example, the resonant frequency f and the quality factor Q are respectively:
wherein R is the radius of the cylinder, l' is the length of the cylinder, c is the speed of light, mu is the magnetic conductivity, and sigma is the electrical conductivity.
The nut 16 is rotated so that the upper diamond anvil 8 and the lower diamond anvil 14 press the sample 13. Taking the example of the metallization transition, sample 13 undergoes a metallization transition from a non-metal to a metal at high pressure. Before the pressure is not enough to enable the sample 13 to generate the metallization conversion, the sample 13 is non-metal, and meanwhile the electric field condition in the DAC detection unit 3 is observed, and through an electric field distribution diagram, the maximum electric field exists at the sample cavity 12 and influences the wall current distribution. When the sample 13 is non-metal, it is equivalent to the resonant cavity 9 having a hole at the sample cavity 12, and the equivalent hole at the sample cavity 12 will affect the sealing property of the resonant cavity, the distribution state of the wall current, and further the resonance state. Under the action of high pressure, when the sample 13 is converted from nonmetal to metal, the resonant cavity 9 is a complete cavity, so that the resonant frequency f, S parameters, the quality factor Q and the impedance Z are correspondingly changed, the frequency difference delta f has a sudden change at a point P along with a pressure change relation curve, and the point P is a metallization conversion phase change point;
measuring a quality factor Q, S parameter, a resonance frequency f and an impedance Z, and judging the high-voltage phase change point of the material metallization transformation through the parameters;
the microwave generator 1 uses a broadband microwave source to input low-power broadband microwaves into the resonant cavity 9, the parameter detection device 4 uses a frequency meter, and when the sample 13 is not pressurized to be nonmetal, the resonant frequency f can be directly measured by the frequency meterNon-metalAnd the resonant frequency f of the sample 13 when it is transformed into metal after pressurizationMetalObtaining the frequency difference delta f of the two states, and reflecting the metallization conversion through the frequency difference delta f of the resonant frequency, wherein the delta f is obtained by the following formula
Δf＝fNon-metal-fMetal (5)。
Further, step E, based on the selected types of the microwave generator 1 and the parameter detection device 4, determining the material metallization transition high-voltage phase transition point by measuring the quality factor Q, S parameter, the resonant frequency f and the impedance Z, specifically comprising the following steps:
the microwave generator 1 uses a voltage controlled oscillator VCO to sweep frequency, the parameter detection device 4 uses a power meter, an important parameter of the resonant cavity 9 is a quality factor Q value, and a formula (7) is used for recording f in the power meter1，f2F, and Δ F, a quality factor Q can be obtained,
in the formula f1And f2Is a half power point,. DELTA.F is F1And f2The difference between the two can be directly used for detecting the sample metallization transition high-voltage phase change point by using the delta f value, and also can be used for detecting the sample metallization transition high-voltage phase change point by detecting the delta Q value, wherein the delta Q is obtained by the formula (8)
ΔQ＝Q0-QL (8)
Wherein Q is0Is a non-metallic quality factor, QLIs the quality factor of the metallic state.
Further, step E, based on the selected types of the microwave generator 1 and the parameter detection device 4, determining the material metallization transition high-voltage phase transition point by measuring the quality factor Q, S parameter, the resonant frequency f and the impedance Z, specifically comprising the following steps:
the microwave generator 1 and the parameter detection device 4 both use a vector network analyzer, and are combined with the vector network analyzer according to the following formula, so that the quality factor Q, the resonant frequency f, the S parameter value and the impedance Z value can be obtained:
Q0＝QL(1+β) (10)
combining the formula (9) and the formula (10) to obtain
Wherein beta is the coupling coefficient, S12The transmission coefficient is in non-metal state, and when the rectangular resonant cavity working mode is adopted, the quality factor is the combination of formula (2) and formula (11), and the quality factor Q in metal state can be obtainedL(ii) a When the cylindrical resonant cavity working mode is adopted, the quality factor is the combination of the formula (4) and the formula (11), and the metal state quality factor Q can be obtainedL；
The metallization transition can be determined from Δ S, the frequency difference Δ f between the two states, the quality factor Δ Q or the impedance Δ Z, where Δ S ═ S12′-S12″,S12' Transmission coefficient in non-metallic state, S12"is the metallic state transmission coefficient,. DELTA.Z ═ Z '-Z', Z 'is the non-metallic state impedance, Z' is the metallic state impedance, for S12′、S12", Z' and Z" can be measured directly using a vector analyzer.
Compared with the prior art, the invention has the beneficial effects that:
the invention combines the microwave resonant cavity and the diamond anvil cell for detecting the metallization transition and non-metallization transition process of the substance under high pressure, effectively improves the limitation of the traditional high-pressure electrical detection technical method, and has the characteristics of non-contact, no pollution, interference resistance, low power, strong universality and the like. The microwave can be detected without direct contact between the probe electrode and the object to be detected, and the purpose can be achieved. The microwave used in the invention has lower power and generates little radiation, so that pollution is basically not generated. The resonant cavity method has strong anti-interference capability, only detects parameter changes in the resonant cavity, and is basically not influenced by the external electromagnetic environment. The gasket and the sample are convenient to replace, the universality is strong, and the method is widely applied to the research of high-pressure scientific substance metallization conversion.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 is a block diagram of the apparatus for detecting metallization transition of a substance according to the present invention;
FIG. 2 is a block diagram of a DAC detection unit; FIG. 3 is a top view of a DAC detection unit;
FIG. 4 is a graph of frequency difference Δ f versus pressure P;
FIG. 5 is a graph of quality factor Q versus frequency f;
FIG. 6 shows the transmission power PWVersus frequency f;
FIG. 7 is a graph of S parameter versus frequency f;
FIG. 8 is a graph of the electric field distribution of a rectangular resonator;
FIG. 9 is a graph showing the frequency difference of a rectangular resonant cavity as a function of the position X of the sample cavity from the center point;
FIG. 10 is a graph of the frequency difference Δ f versus the initial frequency f for a sample in a rectangular resonatorNon-metalA graph of variation relationship;
FIG. 11 is a graph of the electric field distribution of a circular resonator;
FIG. 12 is a graph showing the frequency difference of a circular resonant cavity as a function of the position X of the sample cavity from a central point;
FIG. 13 is a graph of the frequency difference Δ f versus the initial frequency f for a sample in a circular resonatorNon-metalA graph of variation relationship;
FIG. 14 is a rectangular cavity with respect to S12HFSS simulation graphs of (1);
FIG. 15 is a view of a circular cavity with respect to S12HFSS simulation graphs of (1);
in the figure: 1. the device comprises a microwave generator 2, a microwave transmission line 3, a DAC detection unit 4, a parameter detection device 5, a bolt 6, an upper supporting block 7, a resonant cavity wall 8, an upper diamond anvil cell 9, a resonant cavity 10, silver colloid 11, a gasket 12, a sample cavity 13, a sample 14, a lower diamond anvil cell 15, a lower supporting block 16, a nut 17, an input end 18, an output end 19 and an observation window.
Detailed Description
The invention is further illustrated by the following examples:
the present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures. Meanwhile, in the description of the present invention, the terms "first", "second", and the like are used only for distinguishing the description, and are not to be construed as indicating or implying relative importance.
The invention combines with HFSS finite element simulation technology, can carry out electromagnetic simulation on the rectangular resonant cavity 9 and the cylindrical resonant cavity 9, can estimate the influence of the diamond on the anvil position change and the size change on the detection result in the rectangular resonant cavity 9 and the cylindrical resonant cavity 9 through simulation, and can find out the optimal position of the experimental effect more quickly by combining with the experiment.
As shown in figure 1, the device for detecting the metal transition of a substance under high pressure based on the microwave technology comprises a microwave generator 1, a microwave transmission line 2, a DAC detection unit 3 and a parameter detection device 4. The DAC detection unit 3 is respectively connected with the microwave generator 1 and the parameter detection device 4 through the microwave transmission line 2.
As shown in fig. 2, the DAC detection unit 3 is a four-column DAC, and includes an upper support block 6, a resonant cavity wall 7, an upper diamond anvil cell 8, a spacer 11, a sample cavity 11 formed at the center of the spacer 11, a lower diamond anvil cell 14, a lower support block 15, an input end 17, an output end 18, and an observation window 19.
The resonant cavity wall 7 is positioned below the upper support block 6 and is integrally formed with the upper support block, a gasket 11 is arranged below the resonant cavity wall 7, and the upper support block 6, the resonant cavity wall 7 and the gasket 11 jointly enclose a closed resonant cavity 9 for microwave signal transmission. The resonant cavity 9 can be a rectangular resonant cavity or a circular resonant cavity, and the gasket 11 is tightly contacted with the resonant cavity wall 7 and then bonded together through the conductive silver adhesive 10, so that the resonant cavity is closer to an ideal closed cavity.
The upper diamond anvil 8 is at the same height as the resonant cavity wall 7. The sample cavity 12 is used for containing a sample 13, and the sample 13 is filled with ruby powder and a pressure medium and then is loaded into the sample cavity 12.
Bolt holes are symmetrically formed in four corners of the upper supporting block 6 and the lower supporting block 15, the upper supporting block 6 and the lower supporting block 15 penetrate through the bolt holes of the upper supporting block 6 and the lower supporting block 15 through 4 bolts 5, and meanwhile, the upper supporting block 6 and the lower supporting block 15 are fixed through slow rotation and matching with 4 nuts 16.
The observation window 19 is arranged on the lower support block 15 and coaxial with the upper support block 6, the sample cavity 12 and the lower support block 15. Either the ruby fluorescence spectrum or the raman spectrum can be scaled to pressure through the viewing window 19. Specifically, the ruby fluorescence spectrum manometry is to mix a small amount of ruby powder and a pressure transmission medium with a sample 13 to be measured, put the mixture into a sample cavity 12, use a high-intensity excitation light source to excite the ruby fluorescence R line, collect and record the wavelength shift of the fluorescence by an optical system including a monochromator, and the pressure in the sample cavity 12 depends on the recorded ruby fluorescence wavelength shift. And the pressure measurement by the Raman spectrometer is the same as the pressure measurement by the ruby fluorescence spectrum in the sample loading process. Under high pressure, the Raman vibration peak and the frequency thereof change along with the pressure, and the pressure change can be measured according to the change of the peak value.
The input end 17 and the output end 18 are arranged on the upper support block 6, and the lower ports of the input end and the output end penetrate through the upper support block 6 and extend into the resonant cavity 9. The microwave generator 1 is connected with the input end 17 through a microwave transmission line 2, the microwave generator 1 inputs microwave signals into the resonant cavity 9 through the input port 17 by adopting the microwave transmission line 2 for transmission, the microwave signals can be reflected back and forth in the resonant cavity 9, and when the wavelength is matched with the size of the resonant cavity 9, resonance occurs.
Specifically, the microwave generator 1 may use a Voltage Controlled Oscillator (VCO), a broadband microwave source, or a vector network analyzer. The microwave transmission line 2 uses a waveguide transmission line or a coaxial transmission line when the resonant cavity 9 is a rectangular resonant cavity, and the microwave transmission line 2 uses a coaxial transmission line when the resonant cavity 9 is a circular resonant cavity. The input end 17 may be an SMA adapter or a waveguide adapter in the rectangular resonant cavity, and may be an SMA adapter in the circular resonant cavity. The parameter detection device 4 is connected with the output end 18 through the microwave transmission line 2, microwave signals are led out to the parameter detection device 4, the parameter detection device 4 can use a frequency meter, a power meter or a vector network analyzer, and the working range is at least 15 GHz-25 GHz.
In the invention, the materials of all parts of the DAC detection unit 3 are selected, the upper support block 6 and the lower support block 15 are made of metal materials, the radius of the upper support block is 20-30 mm, and the thickness of the upper support block is 4-7 mm; the anvil surfaces of the upper diamond anvil cell 8 and the lower diamond anvil cell 14 are in a hexadecimal shape or an octagonal shape, the thickness is 2 mm-3 mm, and the bottom area is 4mm2The diameter of the anvil surface ranges from 100 mu m to 1000 mu m; the gasket 11 is made of metal sheets, such as steel sheets, iron sheets, rhenium sheets and copper sheets, and has a radius of 5-12.5 mm and a thickness of 0.2-1 mm. If the cavity is a rectangular cavity 9, the hole is positioned at the position 0 mm-3.5 mm away from the central point X, and the hole diameter is 100 mu m-1000 mu m, which is the same as the diamond anvil surface; if a circular cavity 9 is used, the holes are located 0mm to 2.5mm from the center point X, and the hole diameter is 100 μm to 1000 μm, which is the same as the diamond anvil surface. Wherein, the rectangular resonant cavity and the circular resonant cavity have the same height and are both 2 mm-3 mm.
The invention relates to an assembly of a device for detecting the metallization transition of a substance under high pressure based on a microwave technology, which comprises the following steps:
A. the pad 11 is placed on the lower diamond anvil 14 (aligned by the transparent viewing window 19);
B. a small amount of sample 13 powder was picked up and placed on the anvil surface of the lower diamond anvil 14, and then the sample was pressed into a sheet shape. Picking a little by using a needle tip, putting the sample in the sample cavity 12, filling the sample as much as possible, and compacting the sample;
C. putting the ruby at the center of the anvil surface of the lower diamond anvil cell 14 to ensure that the ruby falls at the center of the sample cavity, and slowly pressing;
D. firstly, screwing a nut to tightly press the gasket 11 and the resonant cavity wall 7, so that the resonant cavity wall 7 is tightly contacted with the gasket 11, and then bonding the resonant cavity wall 7 and the gasket 11 through the silver colloid 10 to ensure the tightness of the resonant cavity 9;
principle of detection of metallic transition
The microwave generator 1 inputs microwave signals into the resonant cavity 9 through the input port 17 by using the microwave transmission line 2, the microwave signals are reflected back and forth in the resonant cavity 9, and when the wavelength is matched with the size of the resonant cavity 9, the relation formulas of the formula (1), the formula (2) or the formula (3) and the formula (4) are met, and resonance occurs.
When the size of the resonant cavity 9 is designed, the size of the resonant cavity 9 is preliminarily calculated through a formula (1), a formula (2), a formula (3) and a formula (4), and the optimal resonant cavity specification is obtained through combination of HFSS simulation and experiments.
If the length and width of the rectangular resonant cavity 9 are both 6 mm-15 mm and the height is 2mm, there are many working modes of the rectangular resonant cavity 9 in this range, taking the TE101 mode of the working mode of the rectangular resonant cavity 9 as an example, the resonant frequency f and the quality factor Q are respectively:
where a is the width of the rectangle, b is the height of the rectangle, l is the length of the rectangle, c is the speed of light, μ is the permeability, and σ is the conductivity. Wherein Q is a quality factor, and may be Q when the sample 13 is a non-metal when not pressurized0When the sample 13 is a metal under pressure, Q may be usedL. f is the resonance frequency, and may be f when the sample 13 is not metallic when not pressurizedNon-metalOr f in the case where sample 13 is a metal under pressureMetal。
If the radius range of the cylindrical resonant cavity 9 is 4 mm-12 mm and the height is 2mm, there are many working modes of the cylindrical resonant cavity 9 in this range, taking the working mode TM010 mode of the cylindrical resonant cavity 9 as an example, the resonant frequency f and the quality factor Q are respectively:
wherein R is the radius of the cylinder, l' is the length of the cylinder, c is the speed of light, mu is the magnetic conductivity, and sigma is the electrical conductivity.
The nut 16 is rotated so that the upper diamond anvil 8 and the lower diamond anvil 14 press the sample 13. Taking the example of the metallization transition, sample 13 undergoes a metallization transition from a non-metal to a metal at high pressure. Before the pressure is not enough to cause the sample 13 to have the metallization transition, the sample 13 is non-metal, and the electric field condition in the DAC detection unit 3 is observed, and through the electric field distribution diagrams in fig. 8 and fig. 11, it can be seen that the maximum electric field exists at the sample cavity 12, which affects the wall current distribution. When the sample 13 is non-metal, it is equivalent to the resonant cavity 9 having a hole at the sample cavity 12, and the equivalent hole at the sample cavity 12 will affect the sealing property of the resonant cavity, the distribution state of the wall current, and further the resonance state. Under the action of high pressure, when the sample 13 is converted from nonmetal to metal, the resonant cavity 9 is a complete cavity, so that the resonant frequency f, the S parameter, the quality factor Q and the impedance Z are correspondingly changed, the frequency difference delta f has a sudden change at a point P along with a pressure change relation curve, and the point P is a metallization conversion phase change point, as shown in fig. 4.
The quality factor Q, S parameter, the resonance frequency f and the impedance Z are measured, and the high-voltage phase change point of the material metal transition can be judged through the parameters.
The following three ways are covered by the detection method according to the difference between the microwave generator 1 and the parameter detection device 4:
the first method is as follows: the microwave generator 1 uses a broadband microwave source to input low-power broadband microwaves into the resonant cavity 9 (non-metallic resonance frequency f)Non-metalResonant frequency f with metallic stateMetalIn the frequency band) when the cavity 9 acts as a filter, the cavity 9 will resonate when a certain wavelength matches the cavity 9 size. The parameter detection device 4 uses a frequency meter. When the sample 13 is not pressurized to be a metal, the frequency meter is usedThe resonant frequency f can be directly measuredNon-metalAnd the resonant frequency f of the sample 13 when it is transformed into metal after pressurizationMetalThereby obtaining the frequency difference Δ f of the two states as shown in fig. 5. Thus, the metallization transition can be reflected by the frequency difference Δ f of the resonance frequency. Wherein Δ f is obtained by the following formula
Δf＝fNon-metal-fMetal (5)
The second method comprises the following steps: the microwave generator 1 uses a voltage controlled oscillator VCO for frequency sweeping and the parameter detection device 4 uses a power meter. An important parameter of the resonant cavity 9 is the Q-value, which indicates the level of the resonant efficiency, the more the power consumption is with respect to the energy stored in the resonant cavity 9, the lower the Q-value of the resonant cavity 9; conversely, the smaller the power consumption, the higher the Q value. As an effective tank, the cavity 9 must have a sufficiently high Q value.
The quality factor Q is defined as:
however, in the experiment, the formula (7) was used, and the power meter was measured by recording f1，f2F, and deltaf, as shown in fig. 6, a quality factor Q can be obtained,
in the formula f1And f2Is a half power point,. DELTA.F is F1And f2The difference between these values is such that the narrower the passband, the higher the Q value, as shown in fig. 5 and 6. From fig. 5, it can be seen that when a material undergoes a metallization transition, Q and f change simultaneously, where the resonance frequency f is the frequency at the peak of the Q-factor, so Δ f can be directly used to detect the metallization transition high-voltage phase change point of the sample, or Δ Q can be obtained from the equation (8) by detecting Δ Q and detecting the metallization transition high-voltage phase change point of the sample
ΔQ＝Q0-QL (8)
The third method comprises the following steps: when the microwave generator 1 uses a vector network analyzer, the parameter detection device 4 also uses a vector network analyzer, because the vector network analyzer can directly provide the microwave source and the parameter detection.
The quality factor Q, the resonant frequency f, the S parameter value and the impedance Z value can be obtained by combining the following formula with a vector network analyzer:
Q0＝QL(1+β) (10)
combining the formula (9) and the formula (10) to obtain
Wherein beta is the coupling coefficient, S12The transmission coefficient in the non-metallic state is shown in FIG. 7.
Or taking the rectangular resonant cavity as the TE101 mode as an example, the quality factor is a combination of the formula (2) and the formula (11), and the quality factor Q of the metal state can be obtainedL(ii) a Working mode TM with cylindrical resonant cavity010Taking the example as an example, the quality factor is a combination of equation (4) and equation (11), and the metal state quality factor Q can be obtainedL。
From fig. 7 (S-f curve), it can be observed that the value of S parameter changes when non-metal is converted to metal. Therefore, the value can be determined from Δ S (Δ S ═ S)12′-S12", wherein S12' Transmission coefficient in non-metallic state, S12"is the metal state transmission coefficient) value. Where f also varies, the metallization transition can be judged from the frequency difference Δ f of the two states. And the quality factor Q, also changes, so the quality factor Delta Q can also be used as the basis for judging the metallization conversion.
The value of the impedance Z can also be obtained from a vector network analyzer. The impedance Z value changes due to metallization transition, capacitance and inductance, so the impedance Delta Z (Z '-Z', wherein Z 'is nonmetal state impedance, and Z' is metal state impedance) can also be used as a metallization transition judgment parameter, and the measurement of the impedance Z is the same as the S parameter, and can be directly measured by a vector network analyzer or indirectly obtained by a Smith chart.
All the above methods are also applicable to non-metal transformation, metal is transformed into non-metal under the action of high voltage, and the quality factor Q, S parameter, impedance Z and resonant frequency f of the metal are changed as in the process of metal transformation, so long as the parameter values of the metal and the non-metal are respectively corresponded.
Example 1
A device for detecting substance metallization transition under high pressure based on microwave technology comprises a microwave generator 1, a DAC detection unit 3 and a parameter detection device 4. The microwave transmission line 2 uses a coaxial transmission line because the rectangular cavity and the circular cavity can both use the coaxial transmission line for microwave transmission. The DAC detection unit 3 uses a four-column DAC.
In the components of the four-column DAC, the upper supporting block 6 and the lower supporting block 15 are made of steel, the radius is 24mm, and the thickness is 5 mm. The anvil surface diameters of the upper diamond anvil 8 and the lower diamond anvil 14 were selected to be 200 μm. The gasket 11 is made of a steel sheet with the radius of 12.5mm and the height of 1mm, and the steel material is selected because the steel has high hardness and is not easy to damage during pressurization. The rectangular resonant cavity 9 has a length and width of 12mm and a height of 2mm, the hole is located at a position 3.5mm away from the central point X (as shown in fig. 9), and the aperture size is 0.2mm, which is the same as the aperture size of the sample cavity 12. The radius of the circular resonant cavity 9 is 5mm, the height is 2mm, the hole is located at the position 1mm away from the central point X (as shown in fig. 12), the hole diameter is 0.2mm, and the material of the resonant cavity 9 is steel. The selection of the materials is the optimal selection through experiments, the optimal standard is the frequency difference delta f of the resonant frequency, and the larger delta f is, the better the device effect is. Since microwaves have high requirements on the smoothness of the device, the inner wall and the outer wall of the resonant cavity and the surface of the support block must be smooth, otherwise, the experiment is subject to large errors. Taking the metallization conversion example, data measurement and analysis are performed.
Through simulation experiments, when the length and width of the rectangular resonant cavity are both 12mm and the height is 2mm, and the sample cavity 12 is located at a distance X of 3.5mm from the central point, the measured metallization transition phenomenon is most obvious (as shown in fig. 9). The measured metallization transition is most pronounced if the sample cavity 12 is located at a distance X of 1mm from the center point at a circular cavity radius of 5mm and a height of 2mm (as shown in fig. 12).
Example 2
The method for detecting the substance metallization transition under high pressure based on the microwave technology comprises the following specific implementation steps:
the microwave generator 1 uses a broadband microwave source, the broadband microwave source is a self-made microwave generator based on Gunn tubes, the parameter detection device 4 uses a frequency meter, and the frequency meter uses a CNT-90XL (DC-27GHz) microwave frequency meter. The metallization transition is detected by the frequency difference Δ f of the two states.
When the resonant cavity is a rectangular resonant cavity, fNon-metal＝22.5612GHz，fMetalThe frequency difference Δ f for the metallization conversion of the sample was obtained at 22.5245GHz, which was 36.7 MHz.
When the cavity is a circular cavity, fNon-metal＝15.7646GHz，fMetalThe frequency difference Δ f for the metallization conversion of the sample was obtained at 15.7338GHz, which is 30.8 MHz.
Example 3
The method for detecting the substance metallization transition under high pressure based on the microwave technology comprises the following specific implementation steps:
the microwave generator 1 uses a voltage controlled oscillator VCO to sweep frequency, an ADF4371 is selected as a voltage controlled oscillation source, a power meter is used as the parameter detection device 4, and a Boonton4500B radio frequency power meter is used as the power meter. The metallization transition is detected by the difference in quality factor Δ Q of the two states.
Record f for unpressurized and pressurized samples 13, respectively1，f2And f, according to the formula (7), Q can be directly calculated0And QLAs can be seen from FIG. 5, in the non-metallic state Q0And metallic state QLThe difference of (a). Since the difference in the resonance frequency f is also large, the metallization of the material can be directly reflected by the frequency difference Δ f.
In a resonant cavity ofRectangular cavity, fNon-metal＝21.4620GHz，fMetalThe frequency difference Δ f for the metallization conversion of the sample was found to be 41.2MHz at 21.4208 GHz.
When the cavity is a circular cavity, fNon-metal＝15.9247GHz，fMetalThe frequency difference Δ f for the metallization conversion of the sample was 31.9MHz at 15.8928 GHz.
When the resonant cavity is a rectangular resonant cavity, Q0＝427.045，QL422.662, the difference in quality factor Δ Q for the metallization of the sample was 4.383.
When the resonant cavity is a circular resonant cavity, Q0＝383.688，QL382.813, the difference in quality factor Δ Q for the metallization of the sample was found to be 0.875.
Example 4
The method for detecting the substance metallization transition under high pressure based on the microwave technology comprises the following specific implementation steps:
when the microwave generator 1 uses a vector network analyzer, the parameter detection device 4 also uses a vector network analyzer, and the vector analyzer uses an Agilent8722ES vector network analyzer. Through the S parameter difference value delta S of the two states and the difference value delta Z of the impedance Z, the impedance Z value and the S parameter value can be directly measured through an Agilent8722ES vector network analyzer.
The device for measuring the metallization transition of the microwave detection substance under high pressure is completely assembled, and meanwhile, the output end 1 of the Agilent8722ES vector network analyzer is connected with the input end SMA port 17 through the coaxial transmission line 2, and the output end SMA port 18 is connected with the Agilent8722ES vector network analyzer signal receiving end 4 through the coaxial transmission line 2.
When the resonant cavity is a rectangular resonant cavity, fNon-metal＝21.2120GHz，fMetalThe frequency difference Δ f for the metallization conversion of the sample was obtained at 21.1654GHz, which was 46.6 MHz.
When the cavity is a circular cavity, fNon-metal＝15.9255GHz，fMetalThe frequency difference Δ f for the metallization of the sample was 53.6MHz at 15.8719 GHz.
In a resonant cavityWhen it is a rectangular resonant cavity, S12′＝-142.38dB，S12-161.30 dB; and Z 'is 30.5 omega, and Z' is 30.39 omega. The difference Δ S in S parameters, which resulted in the metallization of the sample, was 18.92dB, and the difference Δ Z in impedance Z was 0.11 Ω.
When the resonant cavity is a circular resonant cavity, S12′＝-152.01dB，S12-180.53 dB; z' 24.67 Ω and Z "24.62 Ω. The difference Δ S in S parameters, which resulted in the metallization of the sample, was 28.52dB, and the difference Δ Z in impedance Z was 0.05 Ω.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.
Claims (10)
1. A detection device for metal transition of substances under high pressure based on microwave technology is characterized in that: the device is composed of a microwave generator (1), a microwave transmission line (2), a DAC detection unit (3) and a parameter detection device (4);
the DAC detection unit (3) comprises a resonant cavity (9), an upper diamond anvil cell (8) arranged in the resonant cavity (9), a gasket (11), a sample cavity (12) used for containing a sample (13) doped with ruby powder and a pressure transmission medium, a lower diamond anvil cell (14), a lower support block (15), an input end (17), an output end (18) and an observation window (19) arranged on the lower support block (15); the upper diamond anvil cell (8) and the lower diamond anvil cell (14) are symmetrically arranged at the upper side and the lower side of the sample cavity (12); the input end (17) and the output end (18) are arranged on an upper support block (6) forming the resonant cavity (9), the bottoms of the upper support block and the lower support block extend into the resonant cavity (9), and the upper support block (6) and the lower support block (15) are fastened through 4 bolts (5);
the microwave generator (1) is connected with the input end (17) through a microwave transmission line (2), microwave signals are input into the resonant cavity (9) to be transmitted and reflected back and forth, and when the wavelength is matched with the size of the resonant cavity (9), resonance occurs; the parameter detection device (4) is connected with the output end (18) through the microwave transmission line (2), and microwave signals are led out to the parameter detection device (4).
2. The device for detecting the metallization transition of a substance under high pressure based on the microwave technology as claimed in claim 1, wherein: the resonant cavity (9) is a rectangular resonant cavity or a circular resonant cavity and is defined by an upper supporting block (6), a resonant cavity wall (7) and a gasket (11), the upper supporting block (6) and the resonant cavity wall (7) are integrally formed, and the gasket (11) is arranged below the resonant cavity wall (7) and is bonded with the resonant cavity wall (7) through conductive silver adhesive (10).
3. The device for detecting the metallization transition of a substance under high pressure based on the microwave technology as claimed in claim 2, wherein: the sample chamber (12) is arranged in the spacer (11).
4. The device for detecting the metallization transition of a substance under high pressure based on the microwave technology as claimed in claim 2, wherein: the upper diamond anvil block (8) and the resonant cavity wall (7) are the same in height.
5. The device for detecting the metallization transition of a substance under high pressure based on the microwave technology as claimed in claim 1, wherein: the microwave generator (1) is a voltage-controlled oscillator, a broadband microwave source or a vector network analyzer; when the resonant cavity (9) is a rectangular resonant cavity, the microwave transmission line (2) uses a waveguide transmission line or a coaxial transmission line, and when the resonant cavity (9) is a circular resonant cavity, the microwave transmission line (2) uses a coaxial transmission line; the input end (17) is an SMA adapter or a waveguide adapter in the rectangular resonant cavity, and is an SMA adapter in the circular resonant cavity; the parameter detection device (4) is a frequency meter, a power meter or a vector network analyzer.
6. The device for detecting the metallization transition of a substance under high pressure based on the microwave technology as claimed in claim 1, wherein: when the resonant cavity (9) is rectangular, the hole is positioned at the position 0 mm-3.5 mm away from the central point X, the aperture size is 100 mu m-1000 mu m, and the hole size is the same as the diamond anvil surface; when the diamond anvil surface is round, the hole is positioned at the position 0 mm-2.5 mm away from the central point X, the hole diameter is 100 mu m-1000 mu m, and the hole diameter is the same as the diamond anvil surface; the rectangular resonant cavity (9) and the circular resonant cavity (9) have the same height, and are both 2 mm-3 mm.
7. A method for detecting substance metallization transition under high pressure based on microwave technology comprises the following steps:
A. the microwave generator (1) and the parameter detection device (4) are respectively connected with the input end (17) and the output end (18) through a microwave transmission line (2);
B. placing the pad (11) on a lower diamond anvil (14);
C. firstly picking a small amount of sample (13) powder out, placing the sample on the anvil surface of a lower diamond anvil cell (14), picking a small amount of sample by using a needle point to fill a sample cavity (12) as much as possible, and then uniformly placing ruby powder on the sample (13) for prepressing;
D. the upper diamond anvil cell and the lower diamond anvil cell are gradually pressed on the sample cavity (12) by screwing the nut (16), and the upper diamond anvil cell (8) and the resonant cavity wall (7) are the same in height, so that the resonant cavity wall (7) and the gasket (11) can be tightly contacted, and then the resonant cavity wall (7) and the gasket (11) are bonded through the silver colloid (10), so that the tightness of the resonant cavity (9) is ensured;
E. and (3) judging the high-voltage phase change point of the substance metallization transition by measuring the quality factor Q, S parameter, the resonance frequency f and the impedance Z based on the selected types of the microwave generator (1) and the parameter detection device (4).
8. The device for detecting the metallization transition of a substance under high pressure based on the microwave technology as claimed in claim 7, wherein: step E, based on the types of the selected microwave generator (1) and the parameter detection device (4), judging the material metallization transition high-voltage phase change point by measuring the quality factor Q, S parameter, the resonant frequency f and the impedance Z, and specifically comprising the following steps:
the microwave generator (1) inputs microwave signals into the resonant cavity (9) through the input port 17 by using the microwave transmission line (2), the microwave signals are reflected back and forth in the resonant cavity (9), and when the wavelength is matched with the size of the resonant cavity (9), the microwave signals accord with the relational expressions of the formula (1), the formula (2) or the formula (3) and the formula (4), and resonance occurs;
when the size of the resonant cavity (9) is designed, the size of the resonant cavity (9) is preliminarily calculated through a formula (1), a formula (2), a formula (3) and a formula (4), and the optimal resonant cavity specification is obtained through combination of HFSS simulation and experiments;
if the length and width ranges of the rectangular resonant cavity (9) are both 6 mm-15 mm and the height is 2mm, the working modes of the rectangular resonant cavity (9) are many in the range, taking the working mode TE101 mode of the rectangular resonant cavity (9) as an example, the resonant frequency f and the quality factor Q are respectively as follows:
wherein a is the width of the rectangle, b is the height of the rectangle, l is the length of the rectangle, c is the speed of light, mu is the magnetic conductivity, and sigma is the electrical conductivity; wherein Q is a quality factor, and may be Q when the sample (13) is a non-metal when not pressurized0Q may be a value obtained when the sample (13) is a metal under pressureL(ii) a f is a resonance frequency, and f may be a frequency when the sample (13) is not metallic when not pressurizedNon-metalOr f in the case where the sample (13) is a metal when pressurizedMetal；
If the radius range of the cylindrical resonant cavity (9) is 4 mm-12 mm and the height is 2mm, the working modes of the cylindrical resonant cavity (9) are many in the range, taking the working mode TM010 mode of the cylindrical resonant cavity (9) as an example, the resonant frequency f and the quality factor Q are respectively as follows:
wherein R is the radius of the cylinder, l' is the length of the cylinder, c is the speed of light, mu is the magnetic conductivity, and sigma is the electrical conductivity;
rotating the nut (16) to enable the upper diamond anvil cell (8) and the lower diamond anvil cell (14) to pressurize the sample (13); taking the example of the metallization conversion, the sample (13) is subjected to the metallization conversion under high pressure, and is converted from nonmetal to metal; before the pressure is not enough to enable the sample (13) to generate the metallization conversion, the sample (13) is non-metal, the electric field condition in the DAC detection unit (3) is observed at the same time, and the maximum electric field exists at the sample cavity (12) and influences the wall current distribution through an electric field distribution diagram; when the sample (13) is non-metal, the equivalent hole of the resonant cavity (9) at the sample cavity (12) can influence the sealing property of the resonant cavity and the distribution state of wall current, and further influence the resonance state; under the action of high pressure, when a sample (13) is converted from nonmetal to metal, the resonant cavity (9) is a complete cavity, so that the resonant frequency f, S parameters, the quality factor Q and the impedance Z are correspondingly changed, the frequency difference delta f has a sudden change at a point P along with a pressure change relation curve, and the point P is a metallization conversion phase change point;
measuring a quality factor Q, S parameter, a resonance frequency f and an impedance Z, and judging the high-voltage phase change point of the material metallization transformation through the parameters;
the microwave generator (1) uses a broadband microwave source to input low-power broadband microwaves into the resonant cavity (9), the parameter detection device (4) uses a frequency meter, and when the sample (13) is not pressurized to be nonmetal, the resonant frequency f can be directly measured by the frequency meterNon-metalAnd the resonant frequency f of the sample (13) when it is transformed into metal after pressurizationMetalObtaining the frequency difference delta f of the two states, and reflecting the metallization conversion through the frequency difference delta f of the resonant frequency, wherein the delta f is obtained by the following formula
Δf＝fNon-metal-fMetal (5)。
9. The device for detecting the metallization transition of a substance under high pressure based on the microwave technology as claimed in claim 7, wherein: step E, based on the types of the selected microwave generator (1) and the parameter detection device (4), judging the material metallization transition high-voltage phase change point by measuring the quality factor Q, S parameter, the resonant frequency f and the impedance Z, and specifically comprising the following steps:
the microwave generator 1 uses a voltage controlled oscillator VCO to sweep frequency, the parameter detection device 4 uses a power meter, an important parameter of the resonant cavity 9 is a quality factor Q value, and a formula (7) is used for recording f in the power meter1，f2F, and Δ F, a quality factor Q can be obtained,
in the formula f1And f2Is a half power point,. DELTA.F is F1And f2The difference between the two can be directly used for detecting the sample metallization transition high-voltage phase change point by using the delta f value, and also can be used for detecting the sample metallization transition high-voltage phase change point by detecting the delta Q value, wherein the delta Q is obtained by the formula (8)
ΔQ＝Q0-QL (8)
Wherein Q is0Is a non-metallic quality factor, QLIs the quality factor of the metallic state.
10. The microwave-based detection of the metallization transition of a substance under high pressure according to claim 7, wherein: step E, based on the types of the selected microwave generator (1) and the parameter detection device (4), judging the material metallization transition high-voltage phase change point by measuring the quality factor Q, S parameter, the resonant frequency f and the impedance Z, and specifically comprising the following steps:
the microwave generator (1) and the parameter detection device (4) both use a vector network analyzer, and are combined with the vector network analyzer according to the following formula, so that the quality factor Q, the resonant frequency f, the S parameter value and the impedance Z value can be obtained:
Q0＝QL(1+β) (10)
combining the formula (9) and the formula (10) to obtain
Wherein beta is the coupling coefficient, S12The transmission coefficient is in non-metal state, and when the rectangular resonant cavity working mode is adopted, the quality factor is the combination of formula (2) and formula (11), and the quality factor Q in metal state can be obtainedL(ii) a When the cylindrical resonant cavity working mode is adopted, the quality factor is the combination of the formula (4) and the formula (11), and the metal state quality factor Q can be obtainedL；
The metallization transition can be determined from Δ S, the frequency difference Δ f between the two states, the quality factor Δ Q or the impedance Δ Z, where Δ S ═ S12′-S12″,S12' Transmission coefficient in non-metallic state, S12"is the metallic state transmission coefficient,. DELTA.Z ═ Z '-Z', Z 'is the non-metallic state impedance, Z' is the metallic state impedance, for S12′、S12", Z' and Z" can be measured directly using a vector analyzer.
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