Determination of the particle size distribution of magnetic pigments

Characterization of the particle size distribution (PSD) of a magnetic pigment enables the evaluation of the contributions to the noise power spectrum arising from the finite particle volume and the spread in particle size [1], The determination of the particle size distribution will be described for a γ-Fe2O3, a CrO2and a CoZn ferrite pigment using transmission electron microscopy (TEM) after sample preparation. Examination of the micrographs simultaneously yields information concerning particle morphology and formation of clusters. Sample preparation for TEM is described in detail. Measurements of the particle dimensions are obtained from TEM micrographs with a digitizer. The PSD is log normal distributed. Results are compared with BET measurements and discussed with respect to error and reproducibility. Some comments on the effect of the particle size distribution on the noise power spectrum are given.