Fine structure of EPR spectra of Fe3+ in α-Al2O3 crystal, powders, and textured ceramics

In this work, a comparison of the angular dependencies Br(θ) of the fine structure lines for Fe3+ in crystal α-Al2O3 with the location of EPR singularities Bs in polycrystalline samples at the same frequency was made. It was shown that the number and location of the singularities are set by extreme points on curves Br(θ). An identification of singularities by the crystallographic orientation of the crystallites that are formed was carried out. The angular dependence of the intensities of the singularities intensity in ceramic specimens α-Al2O3:Fe3+ was found for their revolution around of an axis, perpendicular to the direction of pressing of the initial preparations. The observed effect was explained by the texturing of disk-like particles of α-Al2O3:Fe3+ during the technological operations of pressing and sintering. It was shown that the orientation distribution of crystallites over the volume of a ceramic plate represents an ellipsoid of revolution around an axis of the sample parallel to the direction of pressing. The anisotropy coefficient of the samples studied equals ≈1.7. A method for the choice of singularities, which can be used as EPR-probes for a correct determination of the anisotropy coefficient in ceramic samples is recommended.