A ceramic article which is resistant to erosion by halogen-containing plasmas used in semiconductor processing. The ceramic article includes ceramic which is multi-phased, typically including two phases to three phases. In a first embodiment, the ceramic is formed from yttrium oxide at a molar concentration ranging from about 50 mole % to about 75 mole %; zirconium oxide at a molar concentration ranging from about 10 mole % to about 30 mole %; and at least one other component, selected from the group consisting of aluminum oxide, hafnium oxide, scandium oxide, neodymium oxide, niobium oxide, samarium oxide, ytterbium oxide, erbium oxide, cerium oxide, and combinations thereof, at a molar concentration ranging from about 10 mole % to about 30 mole %. In a second embodiment, the ceramic article includes ceramic which is formed from yttrium oxide at a molar concentration ranging from about 90 mole % to about 70 mole % and zirconium oxide at a molar concentration ranging from about 10 mole % to about 30 mole %, ,
