Using bone ash as an additive in porcelain sintering

Calcined bovine bone (CBB) is generally used to manufacture high-quality porcelain known as bone china. In these products, the amount of bone ash is about 50%. However, it is known that CBB, in small quantities added to raw materials such as feldspars, can reduce the liquidus temperature and thus promote liquid-phase sintering. The purpose of this study was to evaluate the potential use of bone ash as a sintering promoter of porcelain made by a classical triaxial system. Hard porcelain was prepared with 0, 1, 2, and 5 wt% CBB and sintered at temperatures ranging from 1100 to 1400 °C. For the sample containing 2% CBB, the sintering temperature was reduced by 50 °C relative to 0% CBB, while the sample’s tensile strength was the highest among all samples. Two mechanisms could be observed during porcelain sintering depending on CBB quantities: for 1 and 2% of CBB, the mullite formation determined the final shrinkage without changes on initial sintering temperatures; for 5% the initial sintering temperature was decreased by liquid formation.