Phase compositions of sintered specimens were identified by X-ray diffractometry (X? Pert Pro, Philips, Netherlands). Bulk density and apparent porosity were tested by the Archimedes method in distilled water, while the weight of sintered spherical specimens for the testing was 50 g with the diameter 3–5 mm. True density was tested by Automatic pycnometer (AccuPyc 1330, Micromeritics, American). The test method for cold crushing strength was shown in Fig.