Feldspar Porcelain with High Mechanical Strength

There were studied three compositions, according to the masses vitrified between 1150DG and 1250DGC, placed in the leucite - mullite - silica subsystem. The reference sample (a mullite type one) was obtained from English kaolin and aplite (provided from "Philip's Ravine", Romania) and the other two (mullite - cristobalite type) were made from reference samples mixed with Romanian Uricani's quartz (in proportions of 7.5% and 15%). It was used two different quartz grain size (a fine one and a coarse one). The samples were prepared through classical ceramic technology, by thermal treatment between 1150-1300DGC with 2 hour soaking time. Through X rays diffraction analysis was confirmed the existence of theoretical mineralogical compounds: silica, mullite and orthose. The compressive strengths of samples thermally treated at 1250DGC, 2h were between 98 and 183 MPa range. The highest value was observed for sample with 7.5% fine quartz ( < 100m.m).