Improvement of fired properties in porcelain system by the addition of transition metal oxides

Fired properties of porcelain system were studied as a function of firing temperature in the range 1100 degrees C to 1300 degrees C in presence of 0-4 wt% Cr2O3 additive and 1-5 wt% nickel oxide additive. The results showed that though Cr2O3 additive has negligible effect on the modification of the fired properties of porcelain, but a significant improvement in physical and mechanical properties in the presence of NiO additive was found at 1200 degrees C compared to the without additive batch. Phase analysis showed, along with mullite, nickel aluminate spinel phase formed in the presence of NiO additive. Microstructural analysis confirmed that the morphology of the mullite crystals changed significantly in the presence of NiO additive. 5% NiO here acted as a good additive and helped achieve maximum shrinkage, minimum apparent porosity, higher bulk density and maximum flexural strength at 1200 degrees C.