Methods of fabrication of ceramic mirror blanks

A method of forming a shaped ceramic article, the method comprising:

• forming, via a pressure casting process, a green ceramic body comprising a first surface, an opposing second surface and at least one feature shaped into at least one surface, wherein the pressure casting process comprises:
• pumping a ceramic solution comprising a liquid component and a solid component into a mold cavity comprising at least one featured surface, wherein the mold cavity is defined by a porous top surface wall, a porous bottom surface wall and porous sidewalls, and wherein the liquid component of the ceramic solution flows through the porous walls of the mold cavity and the solid component remains within the mold cavity to pressure cast the green featured ceramic body,
• removing the green ceramic body from the mold cavity, and
• heating the green ceramic body to form a debound featured ceramic part;
• densifying the debound featured ceramic part via a hot-pressing process, wherein the hot-pressing process comprises:
• inserting the debound featured ceramic part into a hot-pressing die,
• pouring a first layer of fill material into the hot-pressing die, the fill material having compression characteristics during hot pressing within about 10% of the compression characteristics of the adjacent debound featured ceramic part, wherein the fill material fills the at least one features,
• applying a first pressure to the debound featured ceramic part in a direction perpendicular to the first surface,
• applying a second pressure to the debound featured ceramic part in a direction perpendicular to the second surface while applying the first pressure,
• heating the debound featured ceramic part while applying the first pressure and second pressure to compress the debound featured ceramic part in a direction of the thickness of the featured ceramic part,
• removing the sintered featured ceramic part from the hot-pressing die, and
• removing the fill material powder to expose the features of the ceramic part.

A method of forming a shaped ceramic article, the method comprising:

• forming a green pressed ceramic body comprising a first surface, an opposing second surface and at least one feature shaped into at least one surface, wherein forming the green pressed ceramic body comprises:
• placing a first wax mold having at least feature within a cavity of a pressing die,
• pouring ceramic powder within the cavity wherein the ceramic powder at least completely covers the first wax mold,
• applying about 30 MPa to about 130 MPa of pressure to the ceramic powder within the cavity to form a green pressed body, and
• separating the first wax mold and the green pressed body:
• heating the green pressed body to form a debound featured ceramic part;
• and
• densifying the debound featured ceramic part via a pressureless sintering process, wherein the pressureless sintering process comprises heating the debound featured ceramic part at a temperature of about 2000 degrees Celsius to about 2400 degrees Celsius in an inert gas atmosphere.