A method includes performing ion beam sputtering with ion assisted deposition to deposit a protective layer on a surface of a body. The protective layer is a plasma resistant rare earth-containing film of a thickness less than 1000 .Math.m. The porosity of the protective layer is below 1%. The plasma resistant rare earth-containing film consists of 40 mol% to less than 100 mol% of Y.sub.2O.sub.3, over 0 mol% to 60 mol% of ZrO.sub.2, and 0 mol% to 9 mol% of Al.sub.2O.sub.3.

The present invention provides a method for making a high strength, small grain size ceramic having a trans-granular fracture mode by rapid densification of a green body and subsequent cooling of the densified ceramic. The ceramic may include dislocations, defects, dopants, and/or secondary phases that are formed as a result of the process and resulting in stress fields capable of redirecting or arresting cracks within the material. This ceramic can maintain transparency from ultraviolet to mid-wave infrared.

The present invention provides a method for making a high strength, small grain size ceramic having a trans-granular fracture mode by rapid densification of a green body and subsequent cooling of the densified ceramic. The ceramic may include dislocations, defects, dopants, and/or secondary phases that are formed as a result of the process and resulting in stress fields capable of redirecting or arresting cracks within the material. This ceramic can maintain transparency from ultraviolet to mid-wave infrared.

A sintered material is provided having a phase of a compound at least containing a rare earth element and fluorine, the sintered material having an L* value of 70 or more in the L*a*b* color space. The crystal grains of the sintered material preferably has an average grain size of 10 μm or less. The sintered material preferably has a relative density of 95% or more. The sintered material preferably has a three-point flexural strength of 100 MPa or more. The sintered material preferably contains no oxygen, or preferably has an oxygen content of 13% by mass or less when containing oxygen. The compound is preferably rare earth element fluoride or oxyfluoride.

A sintered material is provided having a phase of a compound at least containing a rare earth element and fluorine, the sintered material having an L* value of 70 or more in the L*a*b* color space. The crystal grains of the sintered material preferably has an average grain size of 10 μm or less. The sintered material preferably has a relative density of 95% or more. The sintered material preferably has a three-point flexural strength of 100 MPa or more. The sintered material preferably contains no oxygen, or preferably has an oxygen content of 13% by mass or less when containing oxygen. The compound is preferably rare earth element fluoride or oxyfluoride.

A sintered body of the present invention contains yttrium oxyfluoride. The yttrium oxyfluoride is preferably YOF and/or Y.sub.5O.sub.4F.sub.7. The sintered body of the present invention preferably contains 50% by mass or more of yttrium oxyfluoride. The sintered body of the present invention has a relative density of preferably 70% or more and an open porosity of preferably 10% or less. Furthermore, the sintered body of the present invention has a three-point bending strength of preferably 10 MPa or more and 300 MPa or less.

A sintered body of the present invention contains yttrium oxyfluoride. The yttrium oxyfluoride is preferably YOF and/or Y.sub.5O.sub.4F.sub.7. The sintered body of the present invention preferably contains 50% by mass or more of yttrium oxyfluoride. The sintered body of the present invention has a relative density of preferably 70% or more and an open porosity of preferably 10% or less. Furthermore, the sintered body of the present invention has a three-point bending strength of preferably 10 MPa or more and 300 MPa or less.

A method of pressure forming a brown part from metal and/or ceramic particle feedstocks includes: introducing into a mold cavity or extruder a first feedstock and one or more additional feedstocks or a green or brown state insert made from a feedstock, wherein the different feedstocks correspond to the different portions of the part; pressurizing the mold cavity or extruder to produce a preform having a plurality of portions corresponding to the first and one or more additional feedstocks, and debinding the preform. Micro voids and interstitial paths from the interior of the preform part to the exterior allow the escape of decomposing or subliming backbone component substantially without creating macro voids due to internal pressure. The large brown preform may then be sintered and subsequently thermomechanically processed to produce a net wrought microstructure and properties that are substantially free the interstitial spaces.

A method of pressure forming a brown part from metal and/or ceramic particle feedstocks includes: introducing into a mold cavity or extruder a first feedstock and one or more additional feedstocks or a green or brown state insert made from a feedstock, wherein the different feedstocks correspond to the different portions of the part; pressurizing the mold cavity or extruder to produce a preform having a plurality of portions corresponding to the first and one or more additional feedstocks, and debinding the preform. Micro voids and interstitial paths from the interior of the preform part to the exterior allow the escape of decomposing or subliming backbone component substantially without creating macro voids due to internal pressure. The large brown preform may then be sintered and subsequently thermomechanically processed to produce a net wrought microstructure and properties that are substantially free the interstitial spaces.

Disclosed herein are methods for producing an ultra-dense and ultra-smooth ceramic coating. A method includes feeding a solution comprising a metal precursor into a plasma sprayer. The plasma sprayer generates a stream toward an article, forming a ceramic coating on the article upon contact.