Aluminum-containing nitride ceramic matrix composite, method of making, and method of use

A method for forming an aluminum-containing nitride ceramic matrix composite, comprising:

• forming at least one green body comprising a phosphor powder and an aluminum-containing composition, wherein
• the at least one green body is characterized by a porosity between about 10% and about 80%, and
• the phosphor powder comprises at least one phosphor composition, and phosphor powder particles have a D50 diameter between about 100 nanometers and about 500 micrometers;
• and
• heating a sealable container to a temperature between about 400 degrees Celsius and about 800 degrees Celsius and a pressure between about 10 MPa and about 1000 MPa,
• wherein
• the at least one green body, ammonia, and a mineralizer composition are disposed within the sealable container before heating and pressurizing the sealable container,
• the aluminum-containing composition has a purity, on a metals basis, between about 90% and about 99.9999%,
• the fraction of free volume within the sealable container that is filled with liquid ammonia is between about 10% and about 95% before heating and pressurizing the sealable container, and
• the heating the sealable container comprises heating the sealable container for a first period of time to form the aluminum-containing nitride ceramic matrix composite characterized by a phosphor-to-aluminum nitride (AlN) ratio, by volume, between about 1% and about 99%, by a porosity between about 1% and about 50%, and by a thermal conductivity between about 1 watt per meter-Kelvin and about 320 watts per meter-Kelvin.