Hydrothermal method for preparing large single crystals of scandium, yttrium, and lanthanide sesquioxides

1. A method for growing lanthanide oxide crystals having the formula Sc 2 O 3 , comprising the steps of:

dispersing Sc 2 O 3 powder in an aqueous solution having an hydroxide ion concentration of from about 1 to about 30 molar; and

subjecting the solution to a temperature of from about 450° C. to about 700° C. and a pressure of from about 4 kpsi to about 30 kpsi.

2. The method set forth in claim 1 wherein the hydroxide ion concentration is from about 15 to about 25 molar.

3. The method set forth in claim 1 wherein the temperature ranges from about 450° C. to about 550° C.

4. The method set forth in claim 1 wherein the pressure ranges from about 15 kpsi to about 20 kpsi.

5. The method set forth in claim 1 wherein the aqueous solution is subjected to an elevated temperature and pressure for a period of from about one to three weeks.

6. A method for growing lanthanide oxide crystals having the formula Ln 2 O 3 , wherein Ln is selected from the group consisting of the lanthanide elements ranging from La to Lu and Y, comprising the steps of:

dispersing Ln 2 O 3 powder in an aqueous solution having an hydroxide ion concentration of from about 1 to about 30 molar; and

subjecting the solution to a temperature of from about 640° C. to about 750° C. and a pressure of from about 15 kpsi to about 40 kpsi.

7. The method set forth in claim 6 wherein the hydroxide ion concentration is from about 15 to about 25 molar.

8. The method set forth in claim 6 wherein the temperature ranges from about 640° C. to about 750° C.

9. The method set forth in claim 6 wherein the pressure ranges from about 15 kpsi to about 30 kspi.

10. The method set forth in claim 6 wherein the aqueous solution is subjected to an elevated temperature and pressure for a period of from about one to three weeks.

11. A method for growing a lanthanide oxide crystal having the formula Ln x Ln′ (2-x) O 3 wherein Ln x is selected from the group consisting of Sc, Y, Gd, La and Lu, and wherein Ln′ is selected from the group consisting of Er, Pr, Yb, Nd, Ho, Tm, Th, Cr, Ti and any other lanthanide or transition metal having a 3+ ionic charge, comprising the steps of:

dispersing Ln x Ln′ (2-x) O 3 powder in an aqueous solution having an hydroxide ion concentration of from about 1 to about 20 molar; and

subjecting the solution to a temperature of from about 450° C. to about 700° C. and a pressure of from about 10 kpsi to about 30 kpsi.

12. A method for growing a lanthanide oxide crystal having the formula Ln 2 O 3 wherein Ln is selected from the group consisting of Sc, Y, La, Lu, and Gd, comprising the steps of:

providing a pressure vessel having a growth region and a nutrient region;

providing a seed crystal having the formula Ln 2 O 3 wherein Ln is selected from the group consisting of Sc, Y, La, Lu, and Gd;

positioning the seed crystal in the growth region of the pressure vessel;

providing a medium comprising a nutrient and a mineralizer in the nutrient region, the nutrient comprising powdered or microcrystalline Ln 2 O 3 wherein Ln is the Ln of the seed crystal, the mineralizer comprising hydroxide ions; and

heating and pressurizing the vessel such that a growth temperature is produced in the growth region, a nutrient temperature is produced in the nutrient region, and a temperature gradient is produced between the growth region and the nutrient region, whereby growth of the crystal is initiated, the growth temperature ranging from about 450° C. to about 650° C., the nutrient temperature ranging from about 500° C. to about 750° C., the nutrient temperature being higher than the growth temperature and the pressure ranging from about 4 kpsi to about 30 kpsi.

13. A method for growing a lanthanide oxide crystal having the formula Ln x Ln′ (2-x) O 3 wherein Ln is selected from the group consisting of Sc, Y, La, Lu, and Gd, and wherein Ln′ is selected from the group consisting of Er, Pr, Yb, Nd, Ho, Tm, Tb, Cr, Ti and any other lanthanide or transition metal having a 3+ ionic charge, comprising the steps of:

providing a pressure vessel having a growth region and a nutrient region;

providing a seed crystal having the formula Ln 2 O 3 or Ln x Ln′ (2-x) O 3 wherein Ln is selected from the group consisting of Sc, Y, La, Lu, and Gd;

positioning the seed crystal in the growth region of the pressure vessel;

providing a medium comprising a nutrient and a mineralizer in the nutrient region, the nutrient comprising powdered or microcrystalline Ln x Ln′ (2-x) O 3 wherein Ln and Ln′ are the Ln and Ln′ of the seed crystal, the mineralizer comprising hydroxide ions; and

heating and pressurizing the vessel such that a growth temperature is produced in the growth region, a nutrient temperature is produced in the nutrient region, and a temperature gradient is produced between the growth region and the nutrient region, whereby growth of the crystal is initiated, the growth temperature ranging from about 450° C. to about 650° C., the nutrient temperature ranging from about 500° C. to about 750° C., the nutrient temperature being higher than the growth temperature and the pressure ranging from about 4 kpsi to about 30 kpsi.