Process for the preparation of up-conversion phosphors
AssigneeEvonik Operations GmbH
InventorsSimone Schulte, Michael Huth, Stefan Fischer, Christina Janke, Juri Tschernjaew
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Abstract
A process can be used for the preparation of an up-conversion phosphor of the general formula (I): A1-x-y-zB*yB2SiO4:Ln1x,Ln2z, (I). The process involves preparing a mixture, introducing the mixture into a reaction chamber of a thermal apparatus, heating the mixture until a thermal treatment temperature is reached with a heating ramp, thermally treating the heated mixture for a holding time of at least 0.02 h, cooling the thermally treated material to room temperature while maintaining a cooling ramp, and obtaining a silicate-based lanthanoid ion-doped phosphor according to formula (I).
Claims20
A process for the preparation of an up-conversion phosphor of the general formula (I)
- A1-x-y-zB*yB2SiO4:Ln1x,Ln2z, (I)
- wherein
- x=0.0001-0.0500;
- z=0.0000 or z=0.0001 to 0.3000, with the proviso that y=x+z;
- A is selected from the group consisting of Mg, Ca, Sr, and Ba;
- B is selected from the group consisting of Li, Na, K, Rb, and Cs;
- B* is selected from the group consisting of Li, Na, and K;
- Ln1 is selected from the group consisting of praseodymium (Pr), erbium (Er), and neodymium (Nd);
- and
- Ln2 is gadolinium (Gd),
- the process comprising:
- preparing a mixture with:
- i) at least one of
- a lanthanoid salt selected from the group consisting of a lanthanoid nitrate, a lanthanoid carbonate, a lanthanoid carboxylate, and a lanthanoid sulfate and combinations thereof;
- and/or
- a lanthanoid oxide,
- wherein a lanthanoid ion in the lanthanoid oxide or lanthanoid salt is selected from the group consisting of praseodymium, gadolinium, erbium, and neodymium and combinations thereof,
- ii) a silicate or a silicon dioxide,
- iii) at least one alkaline earth metal salt, and
- at least one alkali metal salt including a lithium salt and/or a lithium compound, and optionally further including a sodium salt and/or a potassium salt, and
- optionally
- iv) at least one flux selected from the group consisting of ammonium halide, alkali metal halide, alkaline earth metal halide, and lanthanoid halide,
- introducing the mixture into a reaction chamber of a thermal apparatus,
- heating the mixture until a thermal treatment temperature is reached of from 600° C. to <1000° C., with a heating ramp of from 10° C./h-400° C./h, to obtain a heated mixture,
- thermally treating the heated mixture at a temperature of from 600° C. to <1000° C., with a holding time of at least 0.02 h, to obtain a thermally treated material,
- cooling the thermally treated material to room temperature while maintaining a cooling ramp of from 10° C./h-400° C./h, and
- obtaining a silicate-based lanthanoid ion-doped phosphor according to the general formula (I).
Dependencies are inferred from the claim text.