Borate fluxes in bone china
A critical review of phase equilibria studies on the edge binary and face ternary sections of the quaternary system Na₂O-CaO-B₂O₃-SiO₂ is presented. Phase equilibria has been studied by means of the static quenching technique in the binary subsection CaO,B₂O₃-B₂O₃ and the ternary system Na₂O-CaO-B₂O₃. Phase diagrams are presented for the stable and (general) metastable equilibria in the subsection, along with a discussion on the stability and range of the phases CaO, 2B₂O₃ and 'CBx '. Two previously unreported compounds: Na₂O,CaO,4B₂O₃ and 3Na₂O,6CaO,11B₂O₃ were found in the boron-rich part of the ternary system. Unit cell dimensions and X-ray powder patterns are given. A liquidus diagram and a subsolidus compatibility diagram were determined. There is no evidence of solid solution in the system. The general reaction kinetics in the ternary, the distribution of the major compatibility volumes in the quaternary and the application of borate fluxes in bone china are discussed.