SiAion ceramic and method of making the same

An alpha prime-beta prime SiAION ceramic body, as well as a method for making the same, made from a starting powder mixture that includes silicon nitride powder that has a beta-silicon nitride content with a range having a lower limit equal to zero weight percent and an upper limit equal to about 1.6 weight percent oft he silicon nitride powder. The powder mixture also includes one or more powders that provide aluminum, oxygen, nitrogen, and at least one selected rare earth element to the SiAlon ceramic body wherein the selected rare earth element is selected from three specific groupings of the rare earth elements.