GB885994A - - Google Patents

Abstract

885,994. Ceramic compositions. BRUSH CRYSTAL CO. Ltd. Aug. 24, 1959 [Sept. 17, 1958], No. 29445/58. Class 22. [Also in Group XL(b)] A ceramic composition comprises a base material of lead titanate, lead zirconate and lead stannate in the proportions defined by and within the area A B C D of Fig. 3, and from 0À01% to 1À0% by weight on an oxide basis of at least one of the group iron, nickel and cobalt. Up to 25 atom per cent of the lead in the base material can be replaced by at least one of the group Ba, Ca and Sr and the composition may also contain up to 5% by weight on an oxide basis of at least one of the group Ta, Nb and the rare earths excluding cerium and also up to 1À5% by weight on an oxide basis of at least one of the group Cr, Mo, W, U. The Fe, Ni and Co are added as the oxides or carbonates, the Ba, Ca and Sr as carbonates and the other constituents as the oxides. The preferred composition of the base material lies within the area EFGH of Fig. 3 and the composition is exemplified by the formula Pb. 94 Sr. 06 (Zr. 53 Ti. 47 )O 3 with 0À03% to 1À0% NiO. The base material is prepared by mixing the oxides and firing at 850‹C, in an atmosphere of lead oxide if necessary, to prevent loss of lead. The Fe, Ni and/or Co are then added to the crushed base material, milled, formed by pressing, slip casting or extrusion and then fired at 1280‹C.- 1290‹C. Specifications 780,673, 818,710, 843,918, 843,919, 843,920 and 867,039 are referred to.