A sol-gel method was employed to coat an insulating layer of magnesium oxide on Fe and Co-based amorphous alloy ribbons.(Allied Signal Co.'s Metglas 2605 TCA and AMOS 13A) The effects of coating on magnetic properties such as core loss, coercivity and squareness were studied in straight ribbon and toroidal core forms. Particulary the role of annealing on relief of residual stress therefore on decrease of core loss was investigated.
The main purpose of the insulation coating is to study the effect of the coating on interlaminar eddy current loss in cores. As a secondary effect, studies on the role of the coating on iron loss by introducing residual stress to amorphous ribbon due to thermal expansion coefficient difference between the coating layer and ribbons were also aimed.
In the present work, dc and ac hysteresis loops were measured to understand the effect of the coating on magnetic properties. The core loss was little affected by interlaminar insulation in the frequency range measured in this study. In the case of the Fe base amorphous ribbons, magnetic properties were affected by the surface coating deterimentally and it is due to residual stress induced by the surface coating. The core loss reduction achieved in the case of the Co base amorphous ribbon. One of the reason for this behavior must be associated with much lower magnetostriction than that of the Fe base amorphous ribbon and the other reason may be the difference of cluster formation behavior during annealing under a complex stress induced in the winding process in the Co base amorphous ribbon.
