JP3405275B2 - EPMA determination method for fine substances having the same constituent elements but different composition ratios - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron probe microanalyser (hereinafter referred to as "electron probe microanalyser") for irradiating a measuring object with an electron beam and qualifying or quantifying the elements of characteristic X-rays emitted from the measuring object. EPMA ”), especially, for example, AlFe crystallized particles in aluminum foil for electrolytic capacitors,
Airborne particulate matter collected by an air sampler, and carbides, nitrides, sulfides, etc. in iron and steel, which contain two or more constituent elements that are the same as the object to be measured, and their elemental composition ratios differ, and , EPM suitable for quantifying a plurality of minute substances smaller than the characteristic X-ray generation region during electron beam irradiation
A Quantitative method.

[0002]

2. Description of the Related Art For example, high-purity aluminum (99.9)
% Or more) as the base material, the aluminum foil for electrolytic capacitors contains iron (Fe), silicon (Si), copper (Cu), etc. as impurities, albeit in a small amount, and Fe is mainly Al.
Fe crystallized particles (Al ₆ Fe, Al ₃ Fe, AlFe, AlFe ₃ ) and AlFeSi
It is known that it exists as crystallized particles (α-AlFeSi, β-AlFeSi), and Cu exists as AlCu crystallized particles (Al ₂ Cu, AlCu).

And these crystallized particles are
Crystallized particles, AlFeSi crystallized particles, or
Depending on whether it is AlCu crystallized particles, it affects the etching characteristics of aluminum foil for electrolytic capacitors of aluminum foil, quality characteristics such as capacitance, and AlFe crystallized particles are Al ₆ Fe,
Al ₃ Fe, AlFe, any one of AlFe ₃ , or a ratio thereof, and AlFeSi crystallized particles are α-AlFeSi, β-AlFeSi, or a ratio thereof, and further, AlCu crystallized particles are Al ₂ Cu,
It is considered that any one or the proportion of AlCu has a considerable influence on the etching characteristics of the aluminum foil for electrolytic capacitors and quality characteristics such as capacitance.

Therefore, in the past, in order to improve the etching characteristics and the quality characteristics such as capacitance of the aluminum foil, the sample was dissolved in hot phenol and then diluted with benzyl alcohol, and the obtained solution was diluted with polyphenol. Filtered with a filter made of tetrafluoroethylene (PTFE) to capture insoluble crystallized particles with the filter (that is, phenol method: BU
NSEKI KAGAKU, Vol.33, pp.E495-E498, 1984), which is identified by an X-ray diffraction method (XRD), and elemental analysis is performed by fluorescent X-rays.

However, in this XRD method,
At least a few mg is required as a measurement sample to identify crystallized particles, and crystallized particles of impurities contained in a very small amount in high-purity aluminum such as aluminum foil for electrolytic capacitors are collected to the extent that they can be identified. Requires a lot of labor and time, and even if it is identified as, for example, AlFe crystallized particles, it is difficult to prepare a standard sample in which the existing ratio of each AlFe crystallized particle by compound is known. , It is not possible to accurately measure the abundance ratio of AlFe crystallized particles for each compound from their integrated diffraction intensities. Also, with fluorescent X-rays, a few mg is sufficient as a measurement sample, but since it is an elemental analysis, it cannot be specified for each compound.

Further, for example, a PTFE type T100A type membrane filter (pore size 1.0 μm) is used to collect airborne particulate matter by an air sampler, and the characteristic X-ray intensities of various metal elements are collected by EPMA for the particulate matter. (Kα) is measured, and the result is analyzed by the hierarchical cluster analysis method (Median method) or non-hierarchical cluster analysis method (Se).
ed method) to analyze the origin of particulate matter (BUNS
EKI KAGAKU, Vol.38, pp.515-521, 1989) and carbides, nitrides, sulfides, etc. in steel, non-aqueous solvent-based electrolyte potentiostatic electrolysis extraction separation analysis method, acid dissolution extraction separation analysis method , Iodine-methanol or bromine-by using a method such as halogen dissolution extraction separation analysis method using methyl acetate to selectively dissolve the matrix of the sample and separate the carbide, nitride, sulfide, etc.,
Analyzing with EPMA (Metals Handbook 5
Edition ", revised March 31, 1990, pages 488 to 493).

However, even in the analysis of these airborne particulate matter and carbides, nitrides, sulfides, etc. in steel, it is possible to quantify minute substances containing the same constituent elements but having different elemental composition ratios. However, there is a problem that it is difficult to examine its shape and size, and further its distribution.

[0008]

Therefore, the present inventors have proposed AlFe crystallized particles in aluminum foil for electrolytic capacitors,
Airborne particulate matter collected by an air sampler, and further, such as carbides, nitrides, and sulfides in iron and steel, containing the same constituent elements and having different elemental composition ratios, moreover, at the time of electron beam irradiation As a result of diligent study on an EPMA quantification method capable of quantifying a plurality of minute substances smaller than the characteristic X-ray generation region, the characteristic X-ray intensities from two kinds of constituent elements constituting the minute substance are measured, and the measured characteristics are measured. The relative X-ray intensities of these two kinds of constituent elements were obtained from the X-ray intensities, and the relative X-rays of these two kinds of constituent elements were calculated from the obtained relative X-ray intensities.
The line intensity ratio is calculated, and the relative X-ray intensity ratio of the two constituent elements in this minute substance is used as a threshold value of the relative X-ray intensity ratio of the same two constituent elements for the classification determination obtained by the Monte Carlo simulation method. By conducting a classification determination of the minute substances by comparison, and by quantifying the minute substances from the results of this classification determination, it was found that even if the amount of the minute substances captured on the filter is extremely small, it can be accurately quantified by EPMA, The present invention has been completed.

Therefore, an object of the present invention is to include the same two or more kinds of constituent elements and to have different elemental composition ratios, and
It is an object of the present invention to provide an EPMA quantification method capable of accurately quantifying a plurality of minute substances smaller than the characteristic X-ray generation region at the time of electron beam irradiation to the extent practical with EPMA.

Another object of the present invention is to quantify AlFe crystallized particles, which are present in a high-purity aluminum base material in a trace amount, such as an aluminum foil for electrolytic capacitors, by EPMA, and to analyze the compound (Al ₆ Fe). , Al ₃ Fe, AlFe, AlFe ₃ ), the EPMA quantification method of AlFe crystallized particles in an aluminum substrate can be confirmed.

[0011]

That is, according to the present invention, a plurality of minute substances containing at least the same two kinds of constituent elements, different in their elemental composition ratios, and smaller than the characteristic X-ray generation region during electron beam irradiation. E with EPMA
This is a PMA quantification method, in which a fine substance to be measured is captured on a filter, and the captured fine substance is irradiated with an electron beam,
Characteristic X from two constituent elements excited by electron beam irradiation
The line intensity is measured, and these 2 are calculated from the measured characteristic X-ray intensity.
The relative X-ray intensities of the constituent elements of the species were obtained, and the respective relative X-rays obtained
The relative X-ray intensity ratio between these two types of constituent elements was calculated from the line intensities, and the relative X-ray intensity ratio of the two types of constituent elements in this minute substance was determined by the Monte Carlo simulation method. Differentiating composition ratios by having the same constituent element characterized by performing a classification judgment of a minute substance by comparing with a threshold value of the relative X-ray intensity ratio of the constituent element and quantifying the minute substance from the result of the classification judgment. EP of minute substances
This is the MA quantitative method.

The present invention also provides an EPM of the above-mentioned minute substance.
In the A quantitative method, the sample is an aluminum base material containing AlFe crystallized particles of a minute substance, and the AlFe crystallized particles in this sample are captured on a membrane filter by the phenol method, and then other than Al and Fe are collected on this membrane filter. The conductive metal is vapor-deposited to give conductivity, and the Fe / Al relative X-ray intensity ratio between the constituent elements Al and Fe is determined. The Fe / Al relative X-ray intensity ratio of the AlFe crystallized particles is determined. Of Al ₆ Fe and Al ₃ obtained by the Monte Carlo simulation method.
Fe, AlFe, and AlFe ₃ are compared with a threshold value of the Fe / Al relative X-ray intensity ratio for discriminating and judging, and Al ₆ Fe in AlFe crystallized particles,
This is an EPMA quantification method for AlFe crystallized particles in an aluminum base material, in which Al ₃ Fe, AlFe, and AlFe ₃ are separately determined and quantified.

EPMA used in carrying out the method of the present invention
As a wavelength dispersion type (WavelengthDispersive X-ray A
nalizer), but also energy dispersive (Energ
y dispersive X-ray Analizer).

In the method of the present invention, the method for capturing the fine substance to be measured on the filter is not particularly limited, and a conventionally known method can be adopted depending on the type of the fine substance to be measured. Specifically, for example, the fine substance to be measured is AlFe present in high-purity aluminum.
In the case of crystallized particles such as crystallized particles, AlFeSi crystallized particles, or AlCu crystallized particles, the sample is dissolved in hot phenol and then diluted with benzyl alcohol, and the obtained solution is PT.
Phenol method (BUNSEKI KAGA) to filter insoluble crystallized particles by filtration with FE membrane filter
KU, Vol.33, pp.E495-E498, 1984), and when the fine substance to be measured is airborne particulate matter,
It is a method (BUNSEKI KAGAKU, Vol.38, pp515-521) of collecting with an air sampler using a PTFE type T100A membrane filter (pore size 1.0 μm),
Furthermore, the minute substances to be measured are carbides and nitrides in steel,
In the case of sulfide, etc., non-aqueous solvent system electrolyte potentiostatic electrolysis extraction separation analysis method, acid dissolution extraction separation analysis method, halogen dissolution extraction separation analysis method using iodine-methanol or bromine-methyl acetate etc. ("Metals Handbook, 5th Edition," edited by the Institute of Metals, March 31, 1990, revised pages 488-493).

The filter used for trapping the fine substance used herein may be a conductive substance or a non-conductive substance, and the pore size thereof is expected to be a minute substance. Any size may be used as long as it can reliably capture the minute substance in consideration of the size. For example, when the fine substance to be measured is crystallized particles such as AlFe crystallized particles, AlFeSi crystallized particles, or AlCu crystallized particles present in high-purity aluminum, P with a pore diameter of about 0.1 μm is used.
A TFE membrane filter is used, and when the measurement target is a particulate matter in the air, a PTFE membrane filter with a pore size of about 1.0 μm is used. In the case of the above-mentioned carbides, nitrides, sulfides, etc., a PTFE membrane filter having a pore diameter of about 0.2 μm is used.

If the filter used is electrically conductive, the elements constituting the electrically conductive filter form the minute substance to be measured and are irradiated with an electron beam to measure the characteristic X-ray intensity. It is necessary to be an element other than the above two constituent elements, and if the filter used is non-conductive such as an organic substance, the characteristic X-ray intensities of the two constituent elements are irradiated by electron beam irradiation. Prior to measurement, it is preferable to vapor-deposit a metal element other than the above-mentioned two kinds of constituent elements on this non-conductive filter to impart conductivity.

The electron beam irradiation conditions such as acceleration voltage, sample absorption current, and measurement time for measuring the characteristic X-ray intensity by EPMA are the types of the minute substances to be measured and the two types of the minute substances. In consideration of the types of constituent elements, the type of filter, and the like, it is determined so that the minimum sample absorption current that can obtain the resolution necessary for discriminating a minute substance can be secured.

Further, the threshold value of the relative X-ray intensity ratio between the two constituent elements for the classification determination is determined based on the result of the Monte Carlo simulation by performing the electron beam trajectory simulation according to the Monte Carlo method.

In this Monte Carlo simulation, the trajectory of electrons is assumed to be a polygonal line, and one line segment of this polygonal line is defined as the mean free path, and the angle (scattering angle) between one line segment and the next line segment is defined. ) Is the probability corresponding to a certain random number, and the model is assumed to lose the electron energy for each line segment, and the electron energy loss (Δ
E) calculation formula (1), scattering angle (ω) and rotation angle (φ) calculation formula (2), mean free path calculation formula (3), probability of electron collision with element (P) calculation formula The relative X-ray intensity is calculated based on each of the equations (4), the equation (5) of the position after electron scattering, and the equation (6) of the generated X-ray quantum number.

Calculation formula of electron energy loss (ΔE) (1) When E> 6.338J ΔE [Kev / cm] = 7.85 × 10 ⁴ ρΣ [ZC / A · ln (1.16
6 E / J)] / EE When E ≦ 6.338 J ΔE [Kev / cm] = 7.85 × 10 ⁴ ρΣ (ZC / A / J ^1/2 ) /
1.26E ^1/2 Calculation formula of scattering angle (ω) and rotation angle (φ) (2) cos (ω, radian) = 1-2βR / (1 + β−R) φ (radian) = 2πR Mean free path (λ) Formula (3) λ [cm] = [(0.0554E × 10 ³ ) / ρ] × {ΣA
C / [Z ^1/3 (Z + 1)]} × 10 ^-8 [where E is the electron owning energy (Kev), A is the atomic weight, and ρ is the density in the above formulas (1) to (3). (g /
cm ³ ), Z is atomic number, J is ionization potential
(Kev), β is a screening parameter, R is a uniform random number (0 to 1), π is a circular constant (3.14), and C is a composition. ]

Regarding the ionization potential (J), the following three values J: 11.5Z × 10 ⁻³ [Kev] J = 0.00976Z + 0.0588 / Z ^0.19 [Kev] have been hitherto known in the literature. J = {14.0 [1-exp (-0.1Z)] + 75.5
/ Z ^{Z / 7.5} −Z / (100 + Z)} Z × 10 ⁻³ [Kev] has been proposed, and as for the screening parameter (β), the following three values β = [ 5.44Z ^2/3 / E] × 10 ⁻³ β = {3.4Z ^2/3 /E(1.13+3.76α ² ).
^1/2 } × 10 ^-3 β = [3.4Z ^2/3 / E] × 10 ^-3 {where α = [3.69 (Z / E)] × 10 ^-3 } is proposed, Further, regarding the uniform random number (R) used in the calculation formula (2) of the scattering angle (ω), in the literature so far, for example, the central square method (x _{k + 1} = x _k ² several digits in the center) , Multiplication-type phase combination method [x _{k + 1} = λ · x _k (mod,
M)], mixed congruential method [x _{k + 1} = λ · x _k + μ (mod,
M)] and many others have been proposed.

Therefore, there are many combinations for the selection of the ionization potential (J), the screening parameter (β), and the uniform random number (R) used in the calculation formula (2) of the scattering angle (ω). In the present invention, especially regarding the ionization potential (J), J
= 11.5 × Z × 10 ⁻³ [Kev], and for the screening parameter (β) β = [5.44Z ^2/3 /
E] × 10 ⁻³ is preferably used. Furthermore, the scattering angle (ω)
The uniform random number (R) used in the calculation formula (2) is not particularly limited, and it is preferable to use a random number built in a commercially available NEC personal computer or the like. By adopting the combination of this ionization potential (J) and the screening parameter (β), the calculation result by Monte Carlo simulation agrees well with the measured value measured using the standard sample, and the number of incident electrons input to the calculation Can be reduced as much as possible,
It can be calculated without using a large computer.

Here, which atom the electron incident on the multi-component compound collides with is determined by the probability (P) due to the collision cross section of the element, and is represented by the following calculation formula (4). Calculation formula of probability (P) of electron collision with element (4) P = (σC / A) / Σ (σC / A) σ (total scattering cross section) = [πe ⁴ Z (Z + 1)] / [4E
_n ² β (β + 1)] e: electron charge (−4.8029 × 10 ⁻¹⁰ esu) E _n : electron kinetic energy (eE / 300 × 10 ³ ) For example, in the case of a ternary compound, Do so. If 0 <F ≦ P _a ... Collide with a element P _a <F ≦ P _a + P _b ... Collide with b element P _a + P _b <F ≦ P _a + P _b + P _c ... Collide with c element ( However, F is a uniform random number value.)

Further, the position after electron scattering is calculated by the following formula (5) for calculating the position after electron scattering. That is, the X-Y axis is taken on the surface of the sample, and Z in the depth direction.
Taking the axis, and letting the end point position of the nth electron of the electron incident on the origin be (x _n , y _n , z _n ), the position of the (n + 1) th electron is (x _{n + 1} , y _{n + 1} , Z _{n + 1} ) is first scattered by the collision in the direction (ω, φ) from the n-th position (ω: scattering angle from the incident direction due to collision, φ: rotation angle), and The position of the (n + 1) th electron is the direction (θ _{n + 1} , ψ _{n + 1} ) with respect to the (x, y, z) coordinate axis.
It can be expressed as follows.

Calculation formula of position after electron scattering (5) cos (θ _{n + 1} ) = cos (θ _n ) cos (ω) -sin (θ _n ) sin (ω) co
_{s (φ) sin (ψ n} + 1) = Asin (ψ n) + Bcos (ψ n) cos (ψ n + 1) = Acos (ψ n) -Bsin (ψ n) A = [cos (ω) -cos (θ _n ) cos (θ _{n + 1} )] / [sin (θ _n )
sin (θ _{n + 1} )] B = sin (φ) sin (ω) / sin (θ _{n + 1} ) x _{n + 1} = x _n + λ sin (θ _{n + 1} ) cos (ψ _{n + 1} ) × 10 ⁴ (Μ
m) y _{n + 1} = y _n + λ sin (θ _{n + 1} ) sin (ψ _{n + 1} ) × 10 ⁴ (μ
m) z _{n + 1} = z _n + λcos (θ _{n + 1} ) × 10 ⁴ (μm)

Then, the calculation of the generated X-ray quantum number I in which electrons of energy E are generated at the distance λ in the sample is calculated by the following calculation formula (6) of the generated X-ray quantum number, and this calculation is incident. It is repeatedly performed until the energy of the electron becomes lower than the excitation voltage of the element, and the X-ray quantum number is calculated as an integration with that after scattering. Calculation formula of generated X-ray quantum number (6) I = N _A ρQ (E) W _K Cλ / A N _A : Avogadro's number (6.02 × 10 ²³ ) A: Atomic weight ρ: Density (g / cm ³ ) Q (E): Ionization cross section Q (E) · E _k ² = 7.92 × 10 ⁻²⁰ / U · ln
(U) U = E / E _k E _k : Excitation voltage of element [Kev] W _k : Fluorescence yield [W _k = α ⁴ / (1 + α ⁴ )] α = -0.0217 + 0.0332Z-1.14Z ³ ×
Calculation of X-ray quantum number after 10 ⁻⁶ X-ray absorption I ₁ = I exp (−μρd) μ: X-ray mass absorption coefficient d: X-ray passage distance (cm)

Relative X of two constituent elements in a minute substance
The line intensity is X obtained from the sample with the same number of incident electrons.
Calculated as the ratio of the line quantum number and the X-ray quantum number obtained from a 100% sample, and further, from the obtained relative X-ray intensities of these two constituent elements, between these two constituent elements in the minute substance The relative X-ray intensity ratio is calculated, and the relative X-ray intensity ratio is used to sort and determine the minute substances based on this relative X-ray intensity ratio.
A line intensity ratio threshold is determined.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the abundance ratio of AlFe crystallized particles by compound in an aluminum foil for electrolytic capacitors made of high-purity aluminum is determined by a wavelength dispersion type EPMA (Shimadzu EPMA-8705; X-ray extraction angle: 52). .5 °)
A preferred embodiment of the present invention will be described based on an example in the case of quantifying by.

[Preparation of measurement sample (Al by phenol method
Capture of Fe crystallized particles)] 120 ml in a 300 ml flask
Of phenol, heated to 160 ° C. for about 1 minute to remove water, and then 0.2 to 0.3 g of sample aluminum foil was finely shredded and put into a flask, and a reflux condenser was attached. Heat the sample for about 3 minutes to dissolve the sample aluminum foil in phenol, then add 80 ml of benzyl alcohol and cool to room temperature. Transfer the resulting solution to a centrifuge tube and centrifuge (7000 rpm) to remove the supernatant. Then, add benzyl alcohol to the centrifuge tube to disperse the precipitate again, centrifuge again (7000 rpm) to remove the supernatant, and then add methanol and filter with a PTFE membrane filter (pore size 0.1 μm). Then, it was washed with methanol to capture AlFe crystallized particles on this filter.

Next, an ion sputterer [E102 manufactured by Hitachi, Ltd.] was applied to the filter that captured the AlFe crystallized particles.
Ion sputtering] to deposit platinum (Pt) and PT
Conductivity was imparted to the FE membrane filter. The platinum vapor deposition amount at the time of platinum vapor deposition was changed by changing the platinum vapor deposition amount in advance to actually measure the characteristic X-ray intensity by EPMA, and the electron beam irradiation conditions (acceleration voltage, sample It was determined empirically so that the optimum conditions for absorption current, measurement time, etc.) could be obtained.

[Verification of Monte Carlo Simulation]
First, a simulation of electron beam trajectories by the Monte Carlo method
(Monte Carlo simulation)
Energy loss (ΔE) calculation formula (1), scattering angle
Calculation formula (2) of (ω) and calculation formula of mean free path
Ionization potential (J) in (3), screen
Calculation of training parameter (β) and scattering angle (ω)
Many trials have been conducted for the uniform random number (R) used in the equation (2).
Error and result of measurement of bulk standard sample and measurement of known thin film
Based on J = 11.5 × Z × 10 ^-3 [Kev], and β
= [5.44Z^2/3/ E] × 10^-3, And personal
Computer N88 BASIC [manufactured by NEC Corporation]
The uniform random number (R) built into the
Configured the generator.

Further, the Fe / Al relative X-ray intensity ratio measured and determined from minute substances such as AlFe crystallized particles in the aluminum foil captured on the filter is sufficiently larger than the characteristic X-ray generation region in the bulk sample. It is expected that it will be different from the Fe / Al relative X-ray intensity ratio measured from. Therefore, regarding the accelerating voltage of the electron beam that has a large effect on the analysis region, if the accelerating voltage is lower than 15 kV, the resolution of the backscattered electron image is poor,
Since it is difficult to find fine particles fixed in the air like AlFe crystallized particles on the filter, the minimum acceleration voltage is 1
It was decided to study 5 kV and 30 kV as the maximum usable acceleration voltage.

Next, in order to verify the electron beam locus and the X-ray generation program, the physical property values shown in Table 1 were used, and the AlFe compound (Al ₆₎ having a 10 μm square larger than the characteristic X-ray generation region at the acceleration voltages of 15 kV and 30 kV was used. Fe, Al ₃ Fe, AlF
Assuming a bulk sample of e, and AlFe ₃ ), each acceleration voltage is 1
The relative X-ray intensities of Al and Fe generated from this assumed sample were obtained at 5 kV or 30 kV, and then the obtained values of the relative X-ray intensities of the respective elements were converted into the weight% composition by the ZAF method. Compared with. The results are shown in Tables 2 and 3.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

As is clear from the results shown in Tables 2 and 3, the composition obtained by Monte Carlo simulation is in good agreement with the theoretical composition within a relative error of 10%. It was confirmed that the X-ray generation program could be used.

[Acceleration Voltage of Electron Beam] Next, assuming that the assumed compound is a rectangular parallelepiped, the plane direction (X, Y) in which the electron is incident is assumed.
And the depth direction (Z) is changed in the range of 0.2 to 10 μm, and the Fe / Al relative X-ray intensity ratio is calculated when the size of the assumed compound is changed from the minute substance to the bulk body. The effect of size was investigated. The results are shown in Tables 4-11.
Shown in.

[0039]

[Table 4]

[0040]

[Table 5]

[0041]

[Table 6]

[0042]

[Table 7]

[0043]

[Table 8]

[0044]

[Table 9]

[0045]

[Table 10]

[0046]

[Table 11]

As is clear from the results shown in Tables 4 to 11, the AlFe crystallized particles trapped on the filter have a Fe / Al relative X value which does not depend on the size of the particles.
It was found that the classification determination can be performed by the line intensity ratio.

[Setting of Sample Absorption Current and Measurement Time] The count number N of the X-ray intensity has a fluctuation of N ^1/2 , and when the true count number is N ₀ , this count number N ₀ is generally In addition, it is estimated that it is within the range of N-3N ^1/2 <N ₀ <N + 3N ^1/2 . Therefore, when the X-ray intensity of a minute substance is measured by the usual concept, there is a concern that the influence of this statistical variation will appear significantly because the detected X-ray intensity is small.
Therefore, it is necessary to reduce the influence of this statistical fluctuation as much as possible. As a means therefor, it is conceivable to increase the sample absorption current and lengthen the measurement time at each measurement point.

However, the larger the sample absorption current, the better, but if this sample absorption current is increased, the electron beam diameter tends to increase and the current stability tends to deteriorate, so that the same analysis site can be irradiated with the electron beam. It may disappear. Therefore, in order to determine a stable sample absorption current and a measurement time, an actual sample was investigated. As a result, the sample absorption current was 15 nA and the measurement time was 10 seconds when the acceleration voltage was 15 kV, and the sample absorption current was 5 n when the acceleration voltage was 30 kV.
It was found that stable measurement is possible under the measurement conditions of A and measurement time of 10 seconds. However, if a larger sample absorption current can be obtained due to the fixed state of the particles trapped on the filter, it is preferable to take as much sample absorption current as possible.

[Measurement Conditions (Acceleration Voltage, Sample Absorption Current and Measurement Time) and Statistical Variation] Here, the characteristic X-ray intensity measured under the measurement conditions (acceleration voltage, sample absorption current and measurement time) examined above Regarding the influence of statistical fluctuation on the Fe / Al relative X-ray intensity ratio, the assumed Al ₆ Fe compounds shown in Tables 4 and 8 (compound size; X: 0.2 μm, Y: 0.2 μm,
Z: 0.2 μm) was used for the investigation, using the minimum relative X-ray intensities of Fe and Al.

The results show that if the measurement conditions for the sample absorption current and the measurement time are equal to or more than the above-mentioned values, Fe / Fe can be obtained even if there is a statistical variation in the measured characteristic X-ray intensity.
It was found that the value of the Al relative X-ray intensity ratio is hardly affected and the compound can be correctly determined.

As a result, in this embodiment, the accelerating voltage was 15 to 30 kV, and the sample absorption current was 5 to 5 Al, using the wavelength dispersion type EPMA with the X-ray extraction angle of 52.5 °.
Under conditions of 15 nA and measuring time of 10 seconds,
AlFe compounds of AlFe crystallized particles (Al ₆ Fe, Al ₃ Fe, AlFe,
And AlFe ₃ ) can be quantified in the range of fluctuation of the Fe / Al relative X-ray intensity ratio shown in Table 12.

[0053]

[Table 12]

[Comparison Study with Measured Values] In order to verify the threshold value of the Fe / Al relative X-ray intensity ratio obtained by Monte Carlo simulation, only Al ₃ Fe crystallized particles were confirmed by X-ray diffraction extracted by the phenol method. Of the sample, and five different size Al ₃ Fe samples taken from this sample
Characteristic X-rays of Fe and Al using crystallized particles, accelerating voltage of 15 kV, sample absorption current to Al of 15 nA, and measurement time of 10 seconds using a wavelength-dispersive EPMA with an X-ray extraction angle of 52.5 °. The intensity was measured, and the Fe / Al relative X-ray intensity ratio was obtained and compared. As a result, the measured value is 0.8-1.
While it was in the range of 0, the calculated value calculated by the Monte Carlo simulation was 0.8 to 1.3, and it was found that they were in good agreement.

[Regarding AlCu Crystallized Particles and AlFeSi Crystallized Particles in Aluminum Foil for Electrolytic Capacitor] Similar to the case of the AlFe crystallized particles, AlCu crystallized particles in the aluminum foil for electrolytic capacitor made of high-purity aluminum. And AlFe
Abundance ratio of Si crystallized particles by compound is determined by wavelength dispersion type EPMA.
(Shimadzu EPMA-8705; X-ray extraction angle: 5
The thresholds of the Cu / Al relative X-ray intensity ratio and the Fe / Si relative X-ray intensity ratio in the case of quantification by 2.5 °) were obtained by Monte Carlo simulation.

The measurement conditions of the wavelength dispersion type EPMA were set as follows. Accelerating voltage: 15 kV Sample absorption current for aluminum of 100%: 15 n
A Measurement time: 10 seconds X-ray extraction angle: 52.5 °

The physical properties used in the calculations are shown in Table 13, and the results of comparison with theoretical compositions are shown in Table 14 and Table 1.
5 shows.

[0058]

[Table 13]

[0059]

[Table 14]

[0060]

[Table 15]

Further, assuming that the assumed compound is a rectangular parallelepiped, the plane direction (X, Y) and the depth direction (Z) on which electrons are incident are changed within a range of 0.2 to 10 μm, and the size of the assumed compound is made minute. Cu / Al when changing from substance to bulk body
The relative X-ray intensity ratio and the Fe / Si relative X-ray intensity ratio were calculated with the number of incident electrons of 150, and the influence of the size of the assumed compound was investigated. The results are shown in Tables 16-19.

[0062]

[Table 16]

[0063]

[Table 17]

[0064]

[Table 18]

[0065]

[Table 19]

As a result, for the AlCu crystallized particles and the AlFeSi crystallized particles, the accelerating voltage of 15 kV, the sample absorption current of 15 nA with respect to Al, and the measuring time were measured by using the wavelength dispersion type EPMA with the X-ray extraction angle of 52.5 °. Under the condition of 10 seconds, each
AlCu compounds (Al ₂ Cu, AlCu) and AlFeSi compounds (α-Al
It has been found that FeSi, β-AlFeSi) can be quantified in the fluctuation range of the Cu / Al relative X-ray intensity ratio and the Fe / Si relative X-ray intensity ratio shown in Table 20.

[0067]

[Table 20]

[0068]

According to the EPMA quantification method for minute substances of the present invention, a plurality of elements containing the same two or more kinds of constituent elements, having different elemental composition ratios, and having a characteristic X-ray generation region smaller than that of the characteristic X-ray generation region during electron beam irradiation. It is possible to accurately quantify the minute substance of EPMA to the extent practical for EPMA.

Further, according to the EPMA quantification method for minute substances of the present invention, a small amount of AlFe crystallized particles present in a high-purity aluminum substrate such as an aluminum foil for electrolytic capacitors is quantified by EPMA, and Compound (Al ₆ Fe,
Al ₃ Fe, AlFe, AlFe ₃ ).

Claims (4)

(57) [Claims] 1. A plurality of minute substances containing at least the same two kinds of constituent elements, having different element composition ratios, and having a smaller characteristic X-ray generation region at the time of electron beam irradiation, are EP.
This is an EPMA quantification method for quantifying by MA, in which a microscopic substance to be measured is captured on a filter, the captured microscopic substance is irradiated with an electron beam, and characteristic X-rays from two constituent elements excited by the electron beam irradiation. The intensity is measured, and the relative X-ray intensity of these two constituent elements is determined from the measured characteristic X-ray intensity,
The relative X-ray intensity ratio between these two kinds of constituent elements was calculated from the obtained relative X-ray intensities, and the relative X-ray strength ratio of the two kinds of constituent elements in this minute substance was determined by the Monte Carlo simulation method. The same constituent element is characterized in that the minute substance is judged to be discriminated by comparing it with the threshold value of the relative X-ray intensity ratio of the same constituent element for the discrimination judgment, and the minute substance is quantified from the result of the discrimination judgment. EPMA determination method for minute substances with different composition ratios. 2. A filter for trapping a minute substance is a non-conductive filter, which is irradiated with an electron beam to measure the characteristic X-ray intensities of two constituent elements. The EPM of the minute substance according to claim 1, wherein the metallic elements other than the two constituent elements are vapor-deposited to impart conductivity.
A quantitative method. 3. The fine substance to be measured contains the same elements as the matrix elements forming the matrix of the sample containing the fine substance, and the sample is dissolved in a predetermined solvent and filtered to capture it on the filter. Claim 1
Or the EPMA quantification method of the minute substance according to item 2. 4. The sample is an aluminum base material containing AlFe crystallized particles of a minute substance, and the AlFe crystallized particles in this sample are captured on a membrane filter by the phenol method, and then other than Al and Fe are collected on the membrane filter. The conductive metal is vapor-deposited to give conductivity, and the Fe / Al relative X-ray intensity ratio between the constituent elements Al and Fe is obtained.
The Fe / Al relative X-ray intensity ratio of AlFe crystallized particles was obtained by Monte Carlo simulation method. Al ₆ Fe, Al ₃ Fe, AlF
e, and compared with the threshold of the Fe / Al relative X-ray intensity ratio for distinguishing and judging AlFe ₃ , and comparing Al ₆ Fe and Al ₃ F in AlFe crystallized particles
A method for separately determining e, AlFe, and AlFe ₃ to quantify them.
EPMA quantification method of the minute substance of statement.