Fracture toughness of bone china and hard porcelain

Abstract

The fracture toughness of unglazed, commercial samples of bone china and hard porcelain produced by powder pressing spray dried granulated bodies has been determined using the Vickers indentation method. Young's modulus, hardness, and brittleness have also been measured. Although the bone china, with 10% porosity, was considerably more porous than the hard porcelain, with about 5%, its fracture toughness was substantially higher. In addition the brittleness of hard porcelain was higher than that of bone china. It is proposed that these results, which are reflected in the chipping resistance of these whitewares, arise from differences in crystallinity, since there is approximately twice the fraction of crystalline material in bone china as in hard porcelain. The higher porosity of bone china compared to hard porcelain is reflected in the lower Young's modulus of the former.