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電子線マイクロアナライザーによるMg-Ge合金の定量 -Mg Kαに対するGeの質量吸収係数の検討-

MDR Open Deposited

Electron microprobe analysis of Mg-Ge alloy -Examination of the mass absorption coefficient of Ge for MgKα–

MDR Open Deposited

電子線マイクロアナライザーは広く材料の分析に用いられ,定量分析法はZAF法としてほぼ確立されている.しかし,Mg-Ge合金においては,定量分析の結果MgとGeの濃度の合計120wt.%
と異常な値を示した.しかも電子線の加速電圧が高くなるに従ってMgの定量値が上昇する.この誤差の要因として吸収補正のパラメータの一つであるMgKaに対するGeの既存の質量吸収係数の値の不確かさであると推定した.そこで,濃度既知のMg-Ge合金と参照物質MgOおよび金属GeのX線強度比を電子線の加速電圧15kV~30kVの範囲で測定し,その強度比変化を説明するGeのMgKaに対する質量吸収係数として5561±200 cm2/gの値を得た.この値は,広く用いられているHeinrichらの値7510 cm2/gと大きく異なる.この大きな差異は,MgKのエネルギーがGeのLⅠ吸収端とLⅡ吸収端に近接していることから質量吸収係数の値の推定が難しいことに起因していると考えられる.

Electron probe micro analyzer is used for the composition analysis of a wide variety of materials, and its quantification is almost established as a ZAF method. The quantification of MgGe alloy, however, showed an anomalously-high total concentration (ie.120%) of the elements of Mg and Ge. The present analysis of MgGe alloy was not considered to be correct according to the additional fact that the estimating concentration of Mg increase as the increase of accelerating voltage of the electron beam. Because the mass absorption coefficient of Ge for MgKa, is an essential parameter of the ZAF method, we then determined the mass absorption coefficient of Ge for MgKa by using measured X-ray peak intensity ratios of Ge and Mg of MgGe alloy to the standard materials (MgO and Ge). The resulting mass absorption coefficient of Ge for MgKa was 5561±200 cm2/g which were obtained between the electron-beam accelerating voltage of 15kV ~and 30kV. It is smaller than the previous mass absorption coefficient of 7510 cm2/g, which lead the anomalous quantification error. The difference of the mass absorption coefficients must be caused by the difficulty of the measurement of the mass absorption coefficient of Ge for MgKa energy of which is close to the Ge LⅠand LⅡabsorption edges.

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  • 電子線マイクロアナライザーによるMg-Ge合金の定量 -Mg Kαに対するGeの質量吸収係数の検討-
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  • 20/01/2017
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