GB741324A - Improvements in or relating to methods of producing luminescent substances - Google Patents

Abstract

741,324. Luminescent materials. PHILIPS ELECTRICAL INDUSTRIES, Ltd. April 21, 1953 [April 24, 1952], No. 10931/53. Class 39 (1). A method of producing luminescent calciumfiuoro-chloro-phosphate with apatite structure, activated by manganese and antimony, especially for electric discharge tubes, and having the formula where the ratio between fluorine and chlorine is in general between 1 : 1 and 10 : 1, comprises first producing calcium-fluoro-hydroxy-apatite (PFA) containing manganese and antimony by chemical reaction in aqueous solution from compounds containing the elements calcium, fluorine, manganese, antimony and a phosphate group, at least one of which compounds may contain two or more of the elements or one or more of the elements and a phosphate group, and then causing the PFA to react at a temperature between 500‹ and 1200‹ C. with hydrochloric acid or mixing the PFA with calcium chloride and heating to between 800‹ and 1200‹ C. The reaction of the PFA with hydrochloric acid can be produced by passing hydrochloric acid gas over the heated PFA, by heating the PFA with ammonium chloride or by heating the PFA with an alkaline earth chloride and compounds, such as secondary ammonium phosphate, producing hydrochloric acid with the alkaline earth chloride. During the heating the PFA surrounds the substance or the mixture of substances producing the hydrochloric acid. The PFA can be produced by causing an aqueous solution of a calcium compound, such as the nitrate or chloride, and a phosphate, such as secondary ammonium phosphate, solution to flow into a precipitation vessel with such speeds that the ratio between the quantity of phosphate ions and the quantity of calcium ions is always substantially equal to the ratio between the quantities of these ions in the PFA, the activators and the fluorine being added in the form of suitable compounds, such as manganese nitrate, or chloride, antimony chloride, ammonium antimonate and ammonium fluoride, and the contents of the precipitation vessel being stirred and the temperature kept at 50‹ to 100‹ C., preferably 80‹ to 90‹ C. The precipitation vessel may contain an aqueous solution or a suspension of an antimony compound, and an aqueous solution of the calcium compound and manganese compound and a solution of the compounds containing the phosphate group and the fluorine can be caused to flow a the same time from two different supply vessels into the precipitation vessel containing an aqueous suspension of antimony trioxide. During the production of the PFA such a quantity of compounds containing a phosphate group may be added that the PFA contains an excess of unconverted compounds containing phosphate groups. The granular size of the material may be varied by varying the speeds of flow of the two solutions referred to above or by varying the temperature. The PFA may also be produced by mixing very slowly solutions of a calcium salt and an ammonium phosphate. A detailed example of preparation of the luminescent material is described. Specification 578,192 is referred to.