Classification and analysis of the impurity ion clusters in Y3AI5O12

A classification is made of complicated impurity associates for erystals of Y3AI5O12-Lu3AI5O12: A3+ (A3+ = Nd3+, Eu3+ or Pr3+), Y3AI5O12- L3AI2Si3O12: Nd3+ (L2+ = Mg2+, Mn2+ or Ca2+) and Y3AI5O12: Sc3+-(Nd3+, Eu3+). The mechanism is investigated of formation of associations of different type by means of an analysis of the inhomogeneous splitting and broadening of the spectral lines of the A3+ ions. Some possible models are discussed. The effect is studied of the valency and sizes of the impurity ions on the symmetry of the crystal field of the complicated impurity associates.