Hydrothermal methods of fabricating trivalent-metal-ion-doped sapphire crystals

In a crystal-growth autoclave having a chamber wall defining an interior cavity including a crystal-growth zone and a nutrient-dissolution zone situated in fluid communication with the crystal-growth zone, a method of hydrothermally synthesizing sapphire single crystals doped with trivalent metal ions comprising the steps of:

• situating within the crystal-growth zone at least one sapphire-based seed crystal;
• to situating within the nutrient-dissolution zone an aluminum-containing material to serve as nutrient;
• introducing into the cavity an acidic, trivalent-metal-ion-containing growth solution sufficient in quantity to immerse the at least one seed crystal and the nutrient in the growth solution when the solution is heated to a predetermined average temperature within a predetermined process-temperature range;
• maintaining an interior-cavity pressure within a range between and including each of 3.5 kilopounds per square inch and 25 kilopounds per square inch;
• and
• maintaining a temperature differential between the crystal-growth and nutrient-dissolution zones such that the average temperature within the crystal-growth zone is higher than the average temperature within the nutrient-dissolution zone;
• wherein the acidic, trivalent-metal-ion-containing growth solution is selected such that sapphire exhibits retrograde solubility in the solution.