Rhombohedral fluoroberyllium borate crystals and hydrothermal growth thereof for use in laser and non-linear optical applications and devices

1. A method for making rhombohedral fluoroberyllium borate crystals having the formula MBe 2 BO 3 F 2 (MBBF) wherein M is Rb, Cs, or Tl, comprising the steps of:

providing microcrystalline MBe 2 BO 3 F 2 powder, wherein M is Rb, Cs, Tl; and

recrystallizing the microcrystalline MBe 2 BO 3 F 2 in an aqueous solution at a temperature of from about 300° C. to about 600° C. and at a pressure of from about 4 kpsi to about 30 kpsi, the aqueous solution comprising fluoride ions at a concentration of from about 1×10 −6 to about 5 molarity.

2. The method set forth in claim 1 wherein the step of providing microcrystalline MBe 2 BO 3 F 2 powder, wherein M is Rb, Cs, or Tl, comprises reacting MBF 4 , BeO, and a borate selected from the group consisting of B 2 O 3 and H 3 BO 3 in an air atmosphere at a temperature of at least about −700° C. for at least about 1 hour.

3. The method set forth in claim 1 wherein the step of recrystallizing the microcrystalline MBe 2 BO 3 F 2 occurs in an aqueous solution containing fluoride ions at a concentration of from about 0.1 to about 1 molarity.

4. The method set forth in claim 1 wherein the step of recrystallizing the microcrystalline MBe 2 BO 3 F 2 occurs in an aqueous solution at a temperature of from about 400° C. to about 550° C.

5. The method set forth in claim 1 wherein the step of recrystallizing the microcrystalline MBe 2 BO 3 F 2 occurs in an aqueous solution at a pressure of from about 12 kpsi to about 18 kpsi.

6. A method for making rhombohedral fluoroberyllium borate crystals having the formula MBe 2 BO 3 F 2 (MBBF) wherein M is Rb, Cs, or Tl, comprising the steps of:

reacting MBF 4 , BeO, and a borate selected from the group consisting of B 2 O 3 and H 3 BO 3 in an aqueous solution at a temperature of from about 300° C. to about 600° C. and at a pressure of from about 8 kpsi to about 40 kpsi, the aqueous solution further containing fluoride ions at a concentration of from about 0.01 to about 5 molarity.

7. The method set forth in claim 6 wherein the fluoride ions are present in the aqueous solution at a concentration of from about 0.25 to about 1 molarity.

8. The method set forth in claim 6 wherein the temperature ranges from about 450° C. to about 550° C.

9. The method set forth in claim 6 wherein the pressure ranges from about 12 kpsi to about 18 kpsi.

10. A method for making rhombohedral fluoroberyllium borate crystals having the formula MBe 2 BO 3 F 2 (MBBF) wherein M is Rb, Cs, or Tl, comprising the steps of:

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

providing a seed crystal having the formula MBe 2 BO 3 F 2 wherein M is Rb, Cs, or Tl,

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 MBe 2 BO 3 F 2 , the mineralizer comprising fluoride 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 300° C. to about 500° C., the nutrient temperature ranging from about 450° C. to about 600° C., the nutrient temperature being higher than the growth temperature and the pressure ranging from about 8 kpsi to about 40 kpsi.

11. The method set forth in claim 10 wherein the fluoride ions are present in the medium at a concentration of from about 0.01 to about 5 molarity.

12. The method set forth in claim 10 wherein the growth temperature ranges from about 375° C. to about 425° C.

13. The method set forth in claim 10 wherein the nutrient temperature ranges from about 475° C. to about 525° C.

14. The method set forth in claim 10 wherein the pressure ranges from about 12 kpsi to about 18 kpsi.