For the CSP, the as-prepared powders were mixed 1–2 min with 30 wt% deionized water or Ba(OH)2 solution by using a pestle and mortar. The mixture was uniaxially pressed under 500 MPa first at room temperature for 10 min, and then at 220℃. This temperature was maintained for 1.5 h. The as-prepared ceramic pellets were baked at 200℃ overnight to remove possible water residue. And then the ceramic pellets were further annealed at 700 and 900℃ for 3 h with a temperature ramp rate of 10℃/min in air. The densities were measured by using Archimedes’ method, with ethanol as liquid medium.