Amphoteric refractories

Scandium oxide is a refractory white solid (mp 3100 °C) formed on ignition of either the metal or appropriate compounds such as the nitrate, sulfate, and hydroxide. It has amphoteric tendencies denoted by its solubihty in excess alkali from which compounds like K3[Sc(OH)6], containing octahedrally coordinated scandium, have been isolated. In the solid state it has six-coordinate scandium in the Mu203 structure. 

BeO + 20H- + H2O Be(OH>42-It is thus an amphoteric oxide. Beryllium oxide is used for the production of beryllium and beryllium-copper refractories, for high-output transistors, and for printed circuits. The chemical properties of beryllium oxide are similar to those of aluminum oxide. 

Phosphate Bond. Cold-setting bonds for refractories can be formed by reactions between oxides and phosphoric acid, phosphate-phosphoric acid reactions or the direct use of liquid phosphate bonds. The bond is due to the formation of an acid phosphate, with weakly basic or amphoteric oxides. 

Redox reactions, refractories, 33 Reflectance, 67 Refiactive index, 74 Refiactories, acidic, 33 Refiactories, amphoteric, 33 Refiactories, basic, 33 Resistance to crack propagation, 42... 

---