Patent GB-574577-A (GB)
Title: Improvements in or relating to ceramic compositions
IPC: H01B3/02
Filed: 1942-12-08
Abstract: A ceramic composition having high dielectric constants is formed by firing a mix comprising at least 80 per cent of one or more titanates of the alkaline earth metals or lanthanum and/or a mixture of titanium dioxide and an oxide of one or more of these metals in stoichiometrical proportions or of other compounds capable of decomposing to form the oxide without leaving a non-volatile residue on firing.  In addition there may be added up to 20 per cent of lead titanate or up to 10 per cent, but preferably not more than 2 per cent, of one or more of the oxides of beryllium, bismuth, boron, cadmium, chromium, copper, iron, magnesium, manganese, molybdenum, nickel, tungsten, or zirconium. The mix is fired in the normal way to obtain substantially complete vitrification at a temperature of between 1200 DEG  C. and 1400 DEG  C., but preferably above 1360 DEG C.  According to examples, mixes may contain (a) 50-80 per cent barium titanate and 50-20 per cent strontium titanate, (b) 49-45 per cent barium titanate, 50 per cent strontium titanate, and 1-5 per cent lead titanate, and (c) 80-90 per cent strontium titanate and 20-10 per cent lead titanate.  In the manufacture of condensers, the metallic-electrode layers are formed by a firing or chemical reduction process in order to obtain intimate contact.  The mass resulting from firing the mix may be powdered and mixed with an insulating paint, varnish, or enamel, or used as a loading material for mouldable insulating materials such as a natural or a phenolformaldehyde or polyvinyl-chloride artificial resin, or as an impregnant for a fibrous insulating material such as paper or fabric.ALSO:A ceramic composition having high dielectric constants is formed by firing a mix comprising at least 80 per cent of one or more titanates of the alkaline earth metals or lanthanum and/or a mixture of titanium dioxide and an oxide of one or more of these metals in stoichiometrical proportions or of other compounds capable of decomposing to form the oxide without leaving a non-volatile residue on firing.  In addition, there may be added up to 20 per cent of lead titanate or up to 10 per cent, but preferably not more than 2 per cent of one or more of the oxides of beryllium, bismuth, boron, cadmium, chromium, copper, iron, magnesium, manganese, molybdenum, nickel, tungsten or zirconium. The mix is fired in the normal way to obtain substantially complete vitrification, at a temperature of between 1200 DEG  and 1400 DEG  C., but preferably above 1360 DEG  C. According to examples, mixes may contain (a) 50-80 per cent barium titanate and 50-20 per cent strontium titanate; (b) 49-45 per cent barium titanate, 50 per cent strontium titanate, and 1-5 per cent lead titanate; and (c) 80-90 per cent strontium titanate and 20-10 per cent lead titanate.  In the manufacture of condensers, the p metallic-electrode layers are formed by a firing or chemical reduction process in order to obtain intimate contact.  The mass resulting from firing the mix may be powdered and mixed with an insulating paint, varnish, or enamel, or used as a loading material for mouldable insulating-materials such as a natural or a phenol-formaldehyde or polyvinyl-chloride artificial resin, or as an impregnant for a fibrous insulating-material such as paper or fabric.