JP2010122198A - Valence analysis apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a valence analysis apparatus capable of highly accurately and nondestructively determining valence. <P>SOLUTION: The valence analysis apparatus is provided with an X-ray irradiation means for irradiating a sample with X rays radiated from an X-ray tube 1 which being scanned with energy, a spectrum analysis means for analyzing an X-ray absorption spectrum obtained on the sample by the irradiation with X rays and determining the X-ray absorption edge energy of a target element contained in the sample, a correction means for correcting the X-ray absorption edge energy on the basis of the peak energy of characteristic X rays derived from a target material of the X-ray tube 1 or derived from impurities contained in the target material, and a valence computation means for computing the valence of the target element of which the valence is unknown by comparing the X-ray absorption edge energy of a standard sample and that of an analysis sample each after correction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an apparatus for analyzing the valence of an element in a sample containing an element with an unknown valence, and more particularly to an apparatus for analyzing the valence of a transition metal with an unknown valence.

Lithium ion secondary batteries are widely used as small portable power sources for mobile phones, notebook computers, and the like because of their high output and high energy density. In addition, it is also expected as a large power source for hybrid vehicles and electric vehicles, and the development of higher performance lithium ion secondary batteries is desired.
The characteristics of the lithium ion secondary battery are mainly defined by the electrode material. In particular, the positive electrode material plays an important role in improving the characteristics. For this reason, development of the positive electrode material which shows the outstanding battery characteristic becomes a heavy subject.
As positive electrode materials for lithium ion secondary batteries, compounds containing various transition metal oxides are used. The operating voltage and charge / discharge capacity of a lithium ion secondary battery are closely related to the valence of the transition metal oxide in the compound that serves as the positive electrode material. Therefore, accurately measuring the valence of the transition metal oxide is important for the development of a positive electrode material for a lithium ion secondary battery.

One method of quantitative analysis of valence is redox titration. The oxidation-reduction titration method is a method for obtaining the valence of the measurement object from the titration amount of the titrant at the equivalent point by titrating with a titrant. Although the oxidation-reduction titration method is a simple method, the measurement object cannot be analyzed as it is.
On the other hand, since the magnetic measurement method is known as a method for examining the valence of a transition metal, a method for predicting the charge / discharge capacity and operating voltage of a lithium ion secondary battery using the magnetic measurement method has been proposed. (See Patent Document 1). However, the method of Patent Document 1 does not require a specific valence of the transition metal. In addition, it cannot be applied to samples without magnetic interaction.
Patent Document 2 describes a method for analyzing the valence of a transition metal ion based on the presence or absence of a peak at the absorption edge of an X-ray absorption spectrum. However, in the method of Patent Document 2, since an accurate peak position is not obtained, even a minute change in the valence of the transition metal ion cannot be analyzed.
Japanese Unexamined Patent Publication No. 9-80722 JP-A-9-264857

  The problem to be solved by the present invention is to provide a valence analyzer that can determine the valence of an element with high accuracy and non-destructiveness.

The valence analyzer according to the present invention, which has been made to solve the above problems,
a) Irradiating X-rays emitted from an X-ray tube while scanning energy to each of a standard sample containing a target element with a known valence and an analysis sample containing the target element with an unknown valence. X-ray irradiation means for
b) a spectrum analyzing means for analyzing an X-ray absorption spectrum obtained for each of the samples by irradiation with X-rays to obtain an X-ray absorption edge energy of the target element contained in the sample;
c) correction means for correcting the X-ray absorption edge energy based on the peak energy of the characteristic X-ray derived from the target material of the X-ray tube or the characteristic X-ray derived from the impurity contained in the target material;
d) valence calculation means for calculating the valence of the target element whose valence is unknown by comparing the corrected X-ray absorption edge energy of each of the standard sample and the analysis sample.

  The valence is a number indicating how many atoms of a certain element each atom of an element is bonded to. Usually, the valence of a hydrogen atom or a chlorine atom is 1 as a standard, and the valence of an element bonded to n hydrogen atoms or n chlorine atoms is an n valence. Some elements have multiple valences, and transition metals (transition elements) can take many valences. In an element having a plurality of valences, the valence affects the electrical properties, magnetic properties, crystal structure, melting point, etc. of the substance containing the elements. Accordingly, obtaining an accurate valence of an element contained in a substance is important in evaluating various physical properties of the substance.

  It is well known that the X-ray absorption edge of an element changes depending on the valence. Theoretically, the energy at the absorption edge is uniquely determined, but in actual measurement, it is observed with a certain width. Conventionally, methods such as taking an inflection point or taking the midpoint of the maximum and minimum absorption values before and after were used to determine the absorption edge. It could not be determined precisely. Furthermore, there is also a problem in accuracy such as a goniometer used in the X-ray analyzer. As described above, it is very difficult to accurately and accurately obtain the position of the X-ray absorption edge and the amount of change of the X-ray absorption edge in the X-ray absorption spectrum. For this reason, the evaluation of the valence by the X-ray absorption edge has remained qualitative.

On the other hand, the present inventor uses the Boland method (JJBoland, FGHalaka, and JDBaldeschwieler: Phys. Rev. B.28 (1983) 2921) to reproducibly determine the X-ray absorption edge position from the X-ray absorption spectrum. A method for obtaining the X-ray absorption edge position of an element with high accuracy by correcting the X-ray absorption edge position with the characteristic X-ray peak energy derived from the target material of the X-ray tube or the impurities contained in the target material. I found. The present invention is a valence analyzer using this method.
According to the present invention, the valence of an element can be obtained nondestructively and with high accuracy.

FIG. 1 is a schematic configuration diagram of a valence analyzer according to an embodiment of the present invention. The valence analyzer according to the present embodiment is mainly configured of a general X-ray absorption fine structure analysis (XAFS) apparatus, and a sample stage for holding an X-ray tube 1, a curved spectral crystal 2, and a sample 3 ( An incident X-ray detector 4, a transmission X-ray detector 5, and a fluorescence detector 6 are provided. The fluorescence detector 6 is used when measuring the fluorescence intensity. A focal slit 7 is disposed between the curved spectral crystal 2 and the incident X-ray detector 4.
The X-ray tube 1 and the curved spectral crystal 2 are located on a Roland circle. The X-ray tube 1, the curved spectral crystal 2, and the X-ray detectors 4 and 5 are driven by the wavelength scanning drive unit 11 under the control of the control unit 10. The control unit 10 outputs the scanning angle to the data processing unit 12 when controlling the spectral crystal 2 and the like.

The X-ray detector 4 includes a semiconductor detector using a silicon semiconductor, a germanium semiconductor, or a compound semiconductor, a silicon drift detector, a silicon PIN detector, a multi-cathode detector, a proportional counter, a micro calorimeter, a scintillation detector, and the like. Used. When an X-ray photon enters the X-ray detector 4, a pulse signal having a wave height corresponding to the energy of the X-ray photon is generated. This pulse signal is input to the signal processing unit 13. The signal processing unit 13 counts pulse signals having a peak value that falls within a predetermined discrimination range set in advance, and the count value corresponding to the number of pulse signals given within a unit time is used as a data processing unit. 12 is given. In the data processing unit 12, an absorption spectrum is obtained from the intensity of the incident X-ray and the intensity of the X-ray transmitted through the sample. The signal processing unit 13, the data processing unit 12, and the control unit 10 are embodied by a personal computer or the like, and execute various data processing and control by executing predetermined control / processing software installed in advance. Thereby, the below-mentioned X-ray absorbance, absorption spectrum, X-ray absorption edge energy, valence, and the like can be obtained. Therefore, the control unit 10, the data processing unit 12, and the signal processing unit 13 constitute a spectrum analysis unit, a correction unit, and a valence calculation unit of the present invention.
Note that an input unit 14 such as a keyboard and a display unit 15 are connected to the control unit 10.
With the above-described configuration, the X-ray intensity before the sample transmission and the X-ray intensity after the sample transmission are detected by the incident X-ray detector 4 and the transmission X-ray detector 5, respectively.

Next, valence analysis processing using the valence analyzer described above will be described in the order of measurement of an X-ray absorption spectrum, calculation of X-ray absorption edge energy, and determination of valence.
1. X-ray absorption spectrum measurement As described above, the sample is irradiated with X-rays while changing the energy in a predetermined energy range by rotating the spectroscopic crystal 2 and the X-ray detector 4, and the X-ray intensity is sequentially measured. By doing so, an X-ray absorption spectrum is acquired.
Here, X-ray absorption spectra of a compound, a simple substance or a mixture (analytical sample) containing a target element with an unknown valence and a compound, a simple substance or a mixture (standard sample) containing a target element with a known valence are measured. . As the standard sample, a compound, a simple substance or a mixture containing two or more kinds of target elements having different valences is used.

あるいは、透過前のＸ線強度をＩ_０、蛍光Ｘ線の強度をＩ_Ｆ、試料の厚さをtとすると、試料の吸光度μtは次の式で表される。

エネルギーを変化させながら試料にＸ線を透過し、その試料の吸光度を測定する。Ｘ線のエネルギーが、試料中の元素の電子の励起に必要なエネルギー以上になると、Ｘ線が吸収されて電子の励起が起こるため、吸光度が急激に増加する。この点をＸ線吸収端という。 As shown in FIG. 2, when the X-ray intensity before transmission is I ₀ , the X-ray intensity after transmission is I, and the thickness of the sample is t, the absorbance μt of the sample is expressed by the following equation.

Alternatively, if the X-ray intensity before transmission is I ₀ , the fluorescent X-ray intensity is I _F , and the thickness of the sample is t, the absorbance μt of the sample is expressed by the following equation.

While changing the energy, X-rays are transmitted through the sample, and the absorbance of the sample is measured. When the energy of the X-rays exceeds the energy necessary for the excitation of the electrons of the elements in the sample, the X-rays are absorbed and the excitation of the electrons occurs, so that the absorbance increases rapidly. This point is called the X-ray absorption edge.

The X-ray absorption edge shows a specific energy for each element, and the energy changes by a small amount due to the influence of the valence. Therefore, the valence of the transition metal contained in the sample can be quantitatively analyzed by obtaining the energy at the X-ray absorption edge.
For example, FIG. 3 shows X-ray absorption spectra of, for example, FeSO ₄ .7H ₂ O made of divalent Fe and α-Fe ₂ O _{3 made} of trivalent Fe. In each X-ray absorption spectrum, a rapid increase in absorbance due to excitation of divalent Fe and trivalent Fe electrons is observed (Fe-K absorption edge).

2. Determination of X-ray absorption edge and calculation of its energy In this embodiment, the X-ray absorption edge is determined using the Boland method. The Boland method is a method in which X-ray absorption edges are obtained by superposing absorption spectra having different resolutions of the same sample and obtaining the intersection of the absorption spectra obtained at the rising portion of the absorbance (see FIG. 4). Regardless of the resolution of the measurement, it can be said that the spectrum always passes through the absorption edge, so the intersection of spectra with different resolutions represents the absorption edge, which is the principle of the Boland method. As a method of changing the resolution, a method of convolution of Gaussian functions with different slit widths was used.

  The X-ray absorption edge energy is measured by XAFS analysis program MELMS ("EXAFS Study of Cation Distributions in Nickel Zinc Ferrites", Takeshi YAO, Japanese Journal of Applied Physics, Vol. 32, developed by Yao, one of the present inventors. Suppl. 32-2 pp.755-757 (1993) or "EXAFS Study of Cation Distribution in Nickel Aluminate Ferrites", Takeshi YAO, Osamu IMAFUJI, and Hiroshi JINNO, Journal of the American Ceramic Society, Vol.74, pp.314 -317 (1991) or "Crystal Structure of Ga-doped Ba2In2O5 and Its Oxide Ion Conductivity", Takeshi YAO, Yoshiharu UCHIMOTO, Masanori KINUHATA, Toru INAGAKI, Hiroyuki YOSHIDA, Solid State Ionics, Vol.132, pp.189-198 ( 2000)).

3. Determination of valence X-ray absorption edge energy of each sample calculated using the above analysis program, using characteristic X-rays derived from the target material of the X-ray tube 1 or characteristic X-rays derived from impurities mixed in the target material To correct. The impurities are appropriately selected according to the target element in the analysis sample. The impurities may be previously contained in the target material of the X-ray tube 1 by vapor deposition or the like, and may be appropriately selected from one or more impurity elements inevitably mixed in the X-ray tube 1. A specific correction method will be described later.
Thereafter, the amount of change in the X-ray absorption edge energy after correction of each analysis sample with respect to the X-ray absorption edge energy after correction of the standard sample is obtained, and the valence of each analysis sample is obtained by proportional calculation.
Next, specific examples will be described.

1. Measurement of valence with sample containing Fe with known valence Divalent FeSO ₄ .7H ₂ O and trivalent α-Fe ₂ O ₃ were used as standard samples. The analytical sample was prepared by mixing the two kinds of standard samples so that the average valence of Fe was 2.20, 2.40, 2.60 and 2.80. Hereinafter, these analytical samples are referred to as Fe (2.20), Fe (2.40), Fe (2.60), and Fe (2.80).

Next, X-ray absorption spectra were measured for two types of standard samples and four types of analytical samples. For the measurement, an X-ray absorption fine structure analyzer (R-EXAFS2000) manufactured by Rigaku Corporation was used. The specifications of the analyzer are as follows.
X-ray filament: LaB ₆
Target: Mo
Spectroscopic crystal: Ge (220)
Io (incident X-ray) detector: ion chamber
I (Transmission X-ray) detector: Scintillation counter tube voltage: 14kV
Tube current: 150mA
Measurement range: 7.0 keV to 7.7 keV
Each sample used for the measurement was about 30 mg, and the measurement temperature was 20 ° C.
The absorption spectrum of each sample is shown in FIG.

上記式において、
Eo_corrected : 補正後の吸収端エネルギー
Eo_raw : Bolandの方法で求めた、補正前の吸収端エネルギー
E_Ni,sample : 目的物質測定時のNiの特性Ｘ線のピークのエネルギー
E_Ni,standard : 標準物質（FeSO₄・7H₂O）測定時のNiピークのエネルギー
を示す。 Subsequently, the XAFS analysis program MELM is used to calculate the X-ray absorption edge energy in the vicinity of the Fe-K absorption edge from the X-ray absorption spectrum obtained for each sample, and as an impurity in the counter cathode of the X-ray tube 1. Correction was made using the characteristic X-ray peak energy of Ni present.
FIG. 6 shows the incident X-ray spectrum and absorption spectrum of α-Fe ₂ O ₃ . Ni characteristic X-rays appearing in the incident X-ray spectrum have a wavelength peculiar to Ni, and if the tube voltage and tube current are constant, the characteristic X-ray peak position of Ni should be constant. However, there is actually a systematic measurement error due to a deviation of a goniometer or the like. Therefore, the X-ray absorption edge energy was corrected by the deviation amount of the position (energy) of the Ni characteristic X-ray peak in the incident X-ray spectrum of each sample.
The absorption edge energy after correction by the Ni characteristic X-ray peak energy was calculated by the following equation.

In the above formula,
Eo _corrected : Absorption edge energy after correction
Eo _raw : Absorption edge energy before correction, calculated by Boland's method
E _{Ni, sample} : Energy of Ni characteristic X-ray peak when measuring target substance
E _{Ni, standard} : Shows the energy of Ni peak when measuring standard material (FeSO ₄ · 7H ₂ O).

  Thereafter, the valence of Fe contained in each analytical sample was determined by proportional calculation from the amount of change in the absorption edge energy after correction of each analytical sample with respect to the corrected absorption edge energy of the standard sample.

  FIG. 7 shows the corrected X-ray absorption edge energy of each sample, the Fe valence obtained from the energy, and the Fe valence of each analytical sample calculated from the mixing ratio of two kinds of standard samples. The difference between the valence of the analytical sample obtained using the apparatus of this example and the valence obtained from the mixing ratio at the time of sample preparation was 0.03 or less. Therefore, according to the present Example, it was shown that the valence of Fe can be determined simply and with high accuracy.

2. Measurement of valence of Li-ion secondary battery material Using the γ-Fe ₂ O ₃ / KB (Ketjen Black) composite synthesized by the present inventor as the positive electrode and using the negative electrode as the Li metal, a Li-ion cell was created. The sample inserted with Li was used as an analysis sample. Analytical samples of various volumes were prepared by changing the amount of Li inserted. In addition, divalent FeSO ₄ .7H ₂ O and trivalent γ-Fe ₂ O ₃ were used as standard samples.

Here, the X-ray absorption spectrum was measured three times for each sample, the absorption edge was determined by the Boland method for each sample, and the above-described correction was performed. And the valence of Fe of each sample was calculated | required from the absorption edge after correction | amendment, and the valence of the said sample was made into the average value.
The results are shown in FIGS. As is clear from FIG. 8, the valence of Fe decreased with the insertion of Li ions. Also, from the ratio of the change in valence and the total capacity, the capacity due to Fe reduction is about 40% of the total, and the capacity due to the electric double layer of γ-Fe ₂ O ₃ and KB is about 60%. It became clear from FIG.

As a new positive electrode material for Li-ion secondary batteries, compounds containing transition metal oxides have been widely studied. Fe is inexpensive and has abundant resources, and γ-Fe ₂ O ₃ / KB composites are expected to be put to practical use as new cathode materials. In order to evaluate the battery positive electrode material, it is necessary to analyze the mechanism of the electrode reaction in detail, and for that purpose, it is very important to accurately determine the valence of Fe. However, since the capacity due to the valence of Fe and the electric double layer capacity of γ-Fe ₂ O ₃ and KB overlap with the overall charge / discharge capacity, it was not possible to evaluate the valence of Fe from the capacity conventionally. .
In contrast, in this example, the change in the valence of Fe ions accompanying the insertion and desorption of Li ions could be obtained. Moreover, the average value of the valences obtained by measuring the X-ray absorption spectra of the samples a plurality of times was defined as the valence of each sample. Therefore, the characteristics as the battery positive electrode material can be accurately evaluated.

In addition, this invention is not limited to an above-described Example, For example, the following modifications are possible.
As the sample, a sample containing a transition metal other than Fe or a sample containing a typical element can be used. Further, the sample may contain two or more different target elements. Samples can be measured as either solid or liquid. It is also possible to measure the valence of the target element contained in the sample by changing the temperature of the sample.

The configuration of the X-ray absorption fine structure analyzer described above can be modified as follows. For example, in the above embodiment, the X-ray detectors 4 and 5 are rotated together with the X-ray tube 1 and the curved spectral crystal 2, but a PSPC (Position Sensitive Proportional Counter), an imaging plate, a CCD detector, a photographic film, etc. Thus, when using an X-ray detector that simultaneously measures the necessary angle range, the rotation of the X-ray detector is not always necessary.
Further, as a method for measuring while maintaining the positional relationship in which the X-ray tube, the spectral crystal, and the X-ray detector (precisely, the focus slit) are arranged on the circumference of the same circle (Roland circle), FIG. As described above, the X-ray tube and the X-ray detector can be measured by moving the X-ray detector while maintaining a geometrical arrangement in which the radius is constant around the spectral crystal, There is a method of measuring while moving the line detectors on straight lines perpendicular to each other.

  Furthermore, the X-ray intensity before passing through the sample is measured by measuring the X-ray intensity incident on the sample or moving the sample directly to the X-ray detector by placing an ion chamber or Ceratron on the spectroscopic crystal side of the sample. May be incident and measured.

  Instead of measuring the X-ray intensity after passing through the sample, the intensity of fluorescent X-rays generated from the sample by X-ray incidence may be measured. The intensity of fluorescent X-rays is measured by semiconductor detectors using silicon, germanium, or compound semiconductors, silicon drift detectors, silicon PIN detectors, multi-cathode detectors, proportional counters, microcalorimeters, scintillation detectors, CCD detection A vessel or the like is used.

For the measurement of the X-ray absorption spectrum, the following method and apparatus can be used in addition to the X-ray absorption fine structure analyzer described above.
(1) Parallel beam method The parallel beam method measures μt at each point for each wavelength, suppresses X-ray divergence with a slit system, performs wavelength spectroscopy with a flat plate crystal, and then performs a scintillation counter. To detect X-rays.

Optical System FIG. 10 shows an outline of the optical system of the parallel beam method. The X-rays incident from the radiation source are finely narrowed with a slit, passed through a sample, and then monochromatic with a single crystal and led to a detector. In conjunction with the rotation of the central spectral crystal, the detector rotates at twice the speed and selects the wavelength. The optical system includes a slit, a monochromator, a sample holder, a goniometer, and a detector. On the X-ray entrance side of the slit holder, there are lateral restriction slits (three types of 0.1, 0.2, and 0.3 mm), and the entire slit holder can move ± 1 mm in the direction perpendicular to the incident beam. The entrance side slit has 0.1, 0.3, 0.5, 1, 2, 5mm horizontal limiting slit and 1,2,5mm height limiting slit, and the light receiving side slit in front of the detector has 0.1, 0.3, 0.5, 1 , 2,5mm lateral limiting slit can be used.

  The spectroscopic crystal holder can be mounted with a spectroscopic crystal with a maximum width of 100 mm and a length of 25 mm. Each plate single crystal of Ge (111), Ge (220), Si (111), Si (220), and Si (400) is prepared as a spectroscopic crystal. The sample holder exchanges the sample and blank according to the command of the control computer, and measures I and Io. The goniometer has a 2θ axis and a driving angle range from -5 ° to 90 °, and its minimum control angle is 0.002 °. The drive angle range and the minimum control angle of the θ axis are both 1/2 of the 2θ axis. The inside of the X-ray incident side slit holder, the X-ray cover around the spectroscopic crystal, and the light-receiving helium path is replaced with helium to suppress X-ray attenuation. A scintillation counter is used for X-ray detection.

Device control All control of the measuring device is performed by a personal computer (control computer). First, measurement mode (two types of sample and blank are exchanged alternately at each step or fixed to either), measurement angle range, step width, measurement time per step (set separately for sample and blank) The file name and the like for storing the measurement condition and the count value are set. The control computer automatically measures according to the set conditions. The signal from the scintillation counter is counted after being discriminated by an amplifier (for example, Canberra X-RAY AMPLIFIER PULSE HEIGHT ANALYZER Model 1718), and taken into a control computer.

(2) Divergent beam method The divergent beam method measures the X-ray intensity in an appropriate wavelength range at the same time. The divergent beam is incident on a flat plate crystal crystal that is asymmetrically cut from the divergent beam and spreads in the diffraction plane. Detect with one-dimensional PSPC.

Optical System FIG. 11 shows an outline of the divergent beam optical system. A divergent X-ray beam is projected onto a sample, spectrally varied with a flat plate crystal crystal cut asymmetrically and spatially changed, and detected by a one-dimensional PSPC. The goniometer, the spectroscopic crystal holder, the sample holder and the counter arm are the same as the optical system of the parallel beam method. However, in the case of the divergent beam method, the distance between the X-ray source and the spectroscopic crystal changes, and the entire goniometer is arranged closer to the incident beam direction by about 100 mm than in the case of the parallel beam method. The sample is required to have spatial homogeneity in order to pass a wide diverging beam. The incident-side divergence slit continuously adjusts the divergence angle from 0 ° to 5 °. There are three types of height limiting slits: 1,2,5mm. The following six types of asymmetric cut tabular crystals are prepared as spectroscopic crystals.

(i) Si (111) Cut angle-20 ° width 100mm
(ii) Si (220) Cut angle-15 ° width 70mm
(iii) Si (220) Cut angle-20 ° Width 70mm
(iv) Si (400) Cut angle-15 ° Width 50mm
(v) Ge (111) Cut angle-15 ° Width 30mm
(vi) Ge (111) Cut angle-20 ° width 30mm

  The helium path before and after the spectroscopic crystal and the inside of the X-ray cover around the spectroscopic crystal are replaced with helium to suppress the attenuation of X-rays. X-ray detection uses a one-dimensional PSPC installed on a counter arm. PSPC is a PR gas flow system with a position resolution of 200 μm or less, position linearity of ± 1% or less, and an effective length of 100 mm.

Instrument control The angle setting of the spectroscopic crystal and the counter arm and the exchange of the sample and the blank are performed by the same control computer as the parallel beam method. The signal from the PSPC is taken out as a TAC output by the position analysis circuit, and this is subjected to wave height analysis by a multichannel analyzer and input to a personal computer.

The schematic block diagram of the valence analyzer which concerns on one embodiment of this invention. Explanatory drawing of a light absorbency. X-ray absorption spectra of FeSO ₄ · 7H ₂ O and α-Fe ₂ O ₃ . Explanatory drawing of the method of obtaining an X-ray absorption edge. X-ray absorption spectrum of each sample. Incident X-ray spectrum and absorption spectrum of α-Fe ₂ O ₃ . The table | surface which shows the X-ray absorption edge energy and valence of a standard sample and an analysis sample. The table | surface which shows the measurement result of the valence of a Li ion secondary battery material. The figure which shows the relationship between a capacity | capacitance and a valence. Schematic of the optical system of a parallel beam method. Schematic of the divergent beam optical system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... X-ray tube 2 ... Spectral crystal 3 ... Sample 4 ... Incident X-ray detector 5 ... Transmission X-ray detector 6 ... Fluorescence X-ray detector 7 ... Slit 10 ... Control part 12 ... Data processing part 13 ... Signal processing part

Claims (4)

a) Irradiating X-rays emitted from an X-ray tube while scanning energy to each of a standard sample containing a target element with a known valence and an analysis sample containing the target element with an unknown valence. X-ray irradiation means for
b) a spectrum analyzing means for analyzing an X-ray absorption spectrum obtained for each of the samples by irradiation with X-rays to obtain an X-ray absorption edge energy of the target element contained in the sample;
c) correction means for correcting the X-ray absorption edge energy based on the peak energy of the characteristic X-ray derived from the target material of the X-ray tube or the characteristic X-ray derived from impurities contained in the target material;
d) valence analysis means comprising: valence calculation means for calculating the valence of a target element whose valence is unknown by comparing the X-ray absorption edge energy after correction of each of the standard sample and the analysis sample apparatus.   The standard sample is composed of a first standard sample containing a target element having a first valence and a second standard sample containing the target element having a second valence different from the first valence. The valence analyzer according to claim 1.   3. The valence analyzer according to claim 1, wherein the X-ray tube includes a target material previously containing impurities whose characteristic X-ray position is in the vicinity of the X-ray absorption edge of the sample.   The valence analyzer according to any one of claims 1 to 3, wherein the target element contained in the standard sample and the analysis sample is a transition metal.

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