A conventional solid state reaction route was applied to prepare the powders with compossitions.
were used raw materials.The powders were weighed according to the chemical formula,ball-milled for 24 hr. in ethanol,and calcined at 800 for 2 hr.The calcined powder was pressed into circular disks with a diameter of 12 mm. at 100 MPa.The green compacts were sintered in covered alumina crucibles at 975 for 2 hr.in air