Microstructure, internal stresses and fracture mechanics properties of quartzose silicate materials for whitewares

For the production of glassy-crystalline sintered materials, two ceramic bo dies with different initial quartz contents are prepared, spray-dried, pres sed uniaxially and dense-fired at temperatures of 1075 degreesC and 1265 de greesC in a pressureless sintering process. With increasing dense-sintering temperature, the phase composition in the materials changes. At an almost constant total crystallite content of around 60 %, above 1200 degreesC the content of quartz decreases while the content of cristobalite increases. Th is is connected with an increase in the 4-point bending strength from 190 t o 250 MPa. This high strength of a white-wares silicate material is explain ed by changes to its internal stresses.