GB799436A - Manufacture of barium titanyl oxalate and of barium titanate therefrom - Google Patents

Abstract

Barium titanyl oxalate is prepared by calcining at a temperature of at least 1035 DEG C. a mixture of titanium dioxide and barium oxide or a compound yielding barium oxide at the temperature employed, extracting the product of the calcination with excess of aqueous hydrochloric acid, removing insoluble impurities from the extract, precipitating barium titanyl oxalate from the resulting acidic solution with oxalic acid and washing the precipitate with water. The product on calcination yields barium meta-titanate (see Group III). Rutile and barium oxide, hydroxide or carbonate may be used as starting materials. In examples, finely divided TiO2 and BaCO3 in a weight ratio of 2 : 5 are fed through a rotary kiln the temperature of which ranges from 480 DEG C. at the inlet to about 1150 DEG C. at the outlet and after a residence time of 6 hours, the product is heated in concentrated HCl, the resulting mixture is diluted with water and filtered; the solution, said to be of barium and titanium chlorides, is then mixed with a warm aqueous solution of oxalic acid and the slurry of barium titanyl oxalate so formed is filtered and the oxalate is washed with water until free of chlorides and then dried.ALSO:Barium meta-titanate is prepared by calcining at a temperature of at least 1035 DEG C. a mixture of TiO2 and barium oxide or a barium compound, e.g. the hydroxide or carbonate, which yields the oxide at the temperature employed, extracting the product of the calcination with an excess of aqueous hydrochloric acid, removing insoluble impurities from the extract, precipitating barium titanyl oxalate from the resulting acidic solution, said to contain barium and titanium chlorides, by means of oxalic acid, washing the precipitate with water and then calcining it at a temperature of at least about 700 DEG C. to obtain barium meta-titanate. The titanate is obtained in amorphous form if a calcination temperature below about 700 DEG C. is used; a temperature of at least 1000 DEG C. is preferred to obtain a highly purified crystalline product. The titanate is useful for dielectric and piezo-electric purposes. Examples are given.