| 摘要 |
Synthetic garnets of formula M3Me5O12, where M is at least one rare earth metal (atomic No. 58-71, and Y) and Me is at least one trivalent metal, preferably Fe, Al or Ga, are crystallized from a melt of the constituent oxides in a flux of PbF2 and B2O3. The flux may also contain PbO, such that the PbO:PbF2 ratio is 0-1.5:1 and the B2O3:(PbO + PbF2) ratio is 1:20-200 by weight. The constituent oxide:flux ratio may be 1:12.5-2, or 2-3 times as concentrated if seed crystals are added. The Me oxide starting materials may be present in excess of stoichiometric, up to 100% for Fe and Ga, and up to 500% for Al. Minor amounts, e.g. 0.01% of other rare earth or transition metal ions may be incorporated by adding an excess of up to 100% in the flux. The crystals are obtained by cooling the melt from 1300 DEG C. to 950 DEG C. at rates of from 1/2 -10 DEG C/hr. then air-cooled to room temperature, and the flux residue dissolved in boiling 50% HNO3. In the examples Y3Fe5O12, Y3Al5O12 containing Nd, Y3Ga5O12 containing Nd, and Er3Al5O12 containing Tm, are prepared. Also referred to are (Y + Gd)3Fe5O12 and (Y + Er)3 Al5O12 containing Tm. |
