Abstract: A process for obtaining precursors for high critical temperature superconductor ceramics by precipitating salts which are insoluble in water comprises the following stages: A starting solution of soluble salts is prepared in which the cations are in the stoichiometric proportions of the required superconductor phase. A first full precipitation is carried out of a first series of cations at a first value of pH. The first precipitates obtained is filtered out and washed and the filtrate is retained. The pH of the filtrate is changed to a second value and the residual cations are precipitated. The second precipitate is filtered. The first and second precipitates are homogenized. The product obtained is dried, calcined, and ground.

Abstract: A lithium and bromine trifluoride electrochemical cell designed to be discharged after being activated and stored, the cell comprising an anode made of lithium or lithium alloy and a positive current collector made of carbon black, and containing at least one compound that is soluble in bromide trifluoride, and is capable of stabilizing the passivation layer of said anode and of blocking corrosion of said anode during storage, the compound being selected from sulfonates and being at a concentration lying in the range 10.sup.-2 moles per liter to 1 mole per liter. After the cell of the invention has been stored, it restores a large fraction of its initial capacity (curve C).

Abstract: A method of fabricating preforms for making optical fibers by drawing, in which a silica deposit, including a doping agent, is formed in successive layers inside a silica-based tube (1) from a chemical vapor containing a gaseous compound of silicon, oxygen, and a gaseous compound of an element for doping the silica, with the composite tube then being subjected to collapsing so as to cause the empty axial zone (3), the tube hollow, to disappear. The silica of the initial tube is then eliminated, by removal, after which a recharge of silica (5) is made around the remaining cylinder (4) by plasma torch deposition from a gas comprising oxygen and a halogen derivative of silica.