New Accurate Bence-Albee ?-Factors for Oxides and Silicates Calculated from the PAP Correction Procedure

A new α-factor table for the Bence-Albee correction method of quantitative electron microprobe analysi is presented for an accelerating voltage of 15 kV and a take-off angle of 40 degrees. The α-factors were calculated from the full PAP correction with least squares fitting in the range 0.1–50% m/m in C/K-C space, with the assumption that C/K = 1 for C = 1, where C is the weight fraction of the emitting element as oxide or anion in binary oxide-oxide, oxide-anion or anion-anion systems, and K is the relative X-ray intensity ratio between compound and pure oxide or anion. Recently determined mass attenuation coefficients were chosen. X-ray intensities were calculated for binary oxide-oxide, oxide-anion and anion-anion systems. For the twelve major elements that characterise most geological samples, maximum deviations of α-factors in this study were smaller than 10 % and most deviations were less than 1%. The new α-factor table improves the accuracy of the Bence-Albee method compared with previous studies, and provides results as accurate as the full PAP correction when absorption is not large.