Compound based on an alkaline-earth metal, on sulphur and on aluminium, on gallium or on indium, its process of preparation and its use as luminophore

Abstract

The present invention relates to a compound based on an alkaline-earth metal, on sulphur and on aluminium, on gallium or indium, to its process of preparation and to its use as luminophore. The compound of the invention corresponds to the formula AB 2 S 4 , in which A represents an alkaline-earth metal and B aluminum, gallium, or indium and it is characterized in that it is provided in the form of a powder with a residual oxygen content of not more that 1.5% and composed of particles with a mean size of not more than 10 μm. This compound is obtained by a process which contains the following stages: a solution or a suspension comprising salts of the elements A and B is formed, the solution or the suspension is dried by atomization and the product obtained in the preceding stages is reacted with carbon disulphide or with a mixture of hydrogen sulphide and or carbon disulphide. The compound of the invention can be used as a luminophore, in particular in cathodoluminescence.

1 . A compound of formula AB 2 S 4  in which A represents one or more alkaline-earth metals and B represents at least one element selected from aluminium, gallium and indium, characterized in that it is in the form of a powder with a residual oxygen content of not more than 1.5%, more particularly of not more than 1%.  
     
     
         2 . A compound according to    claim 1    characterized in that it is in the form of a powder composed of unmilled particles with a mean size of not more than 10 μm.  
     
     
         3 . A compound of formula AB 2 S 4  in which A represents one or more alkaline-earth metals and B at least one element taken from the group comprising aluminium, gallium or indium, characterized in that it is provided in the form of a powder composed of whole or unmilled particles with a mean size of not more than 10 μm.  
     
     
         4 . A compound according to    claim 3    characterized in that it presents a residual oxygen content of not more than 1.5%, more particularly of not more than 1%.  
     
     
         5 . A compound according to any one of the preceding claims, characterized in that it comprises at least one doping element which confers properties of luminescence on said compound.  
     
     
         6 . A compound according to any one of the preceding claims, characterized in that the particles have a mean size of not more than 5 μm.  
     
     
         7 . A compound according to any one of the preceding claims, characterized in that the particles have a substantially spherical shape.  
     
     
         8 . A compound according to any one of the preceding claims, characterized in that the particles have a dispersion index σ/m of not more than 0.7.  
     
     
         9 . A compound according to any one of the preceding claims, characterized in that it is a pure crystallographic phase.  
     
     
         10 . A compound according to any one of the preceding claims, characterized in that B is gallium.  
     
     
         11 . A compound according to any one of the preceding claims, characterized in that A is strontium.  
     
     
         12 . A compound according to    claim 10    or    11   , characterized in that it is in a pure cubic crystallographic phase.  
     
     
         13 . A compound according to any one of    claims 5    to    11   , characterized in that the doping element is chosen from divalent manganese, divalent rare-earth metals and the group comprising the trivalent rare-earth metals in combination with an alkali metal, said doping element being more particularly europium (II), ytterbium in combination with an alkali metal.  
     
     
         14 . A compound according to any one of the preceding claims, characterized in that the particles comprise a layer based on at least one transparent oxide.  
     
     
         15 . A compound according to one of the preceding claims, characterized in that it is in the form of a powder the particles of which comprise a zinc compound on the surface thereof.  
     
     
         16 . A compound according to    claim 15   , characterized in that the zinc compound has been obtained by reaction of a zinc precursor with ammonia and/or an ammonium salt.  
     
     
         17 . Process for the preparation of a compound according to one of    claims 1    to    13   , characterized in that it comprises 
 forming a solution or a suspension comprising salts of the elements A and B and optionally of a doping element,  
 drying the solution or the suspension by atomization,  
 reacting the product obtained in the preceding step with carbon disulphide, hydrogen sulphide or with a mixture of hydrogen sulphide and of carbon disulphide.  
 
     
     
         18 . Process according to    claim 17   , characterized in that the reaction with said gaseous mixture is carried out at a temperature of from 600 to 1000° C.  
     
     
         19 . Process according to    claim 17    or    18   , characterized in that nitrates are used as salts.  
     
     
         20 . Use of a compound according to any one of    claims 1    to    16    as a luminophore, in particular in cathodoluminescence.  
     
     
         21 . Devise employing cathodoluminescence, characterized in that it comprises a compound according to any one of    claims 1    to    16   .