β-SiAlON wavelength converters and methods of making the same
Methods for producing wavelength converters are described. The methods include sintering a mixture consisting essentially of first particles and second particles to form a sintered article. In embodiments the first particles consist essentially of particles of β-SiAlON or precursors thereof, and the second particles consist essentially one or more sintering aids or precursors thereof. In embodiments the sintered article has a density that is greater than or equal to about 90% of a theoretical bulk density of the mixture, and is configured to convert primary light incident thereon to secondary light, wherein the secondary light exhibits a peak with a full width half maximum of greater than 0 to about 60 nanometers (nm) within a wavelength range of about 495 nm to about 600 nm.
1. A method, comprising:
sintering a mixture consisting essentially of first particles and second particles to form a sintered article; and
providing the sintered article on a light source as a wavelength converter;
wherein said first particles consist essentially of particles of β-SiAlON or particles of one or more precursors of said β-SiAlON;
wherein said second particles consist essentially of particles of at least one sintering aid wherein said at least one sintering aid is yttrium aluminum garnet (Y 3 Al 5 O 12 ), spinel (MgAl 2 O 4 ) or a combination thereof;
wherein said sintered article has a density that is greater than or equal to about 90% of a theoretical bulk density of said mixture of first particles and second particles;
wherein said sintered article is configured to convert primary light incident thereon to secondary light, wherein said secondary light exhibits a peak with a full width half maximum of greater than 0 to about 60 nanometers (nm) within a wavelength range of about 495 nm to about 600 nm; and
wherein the light source is configured to emit primary light for at least partial conversion into the secondary light by the sintered article.
2. The method of claim 1 , wherein said at least one sintering aid comprises the combination of Y 3 Al 5 O 12 and MgAl 2 O 4 .
3. The method of claim 1 , wherein said sintering comprises subjecting said mixture to a pressureless sintering process.
4. The method of claim 3 , wherein said sintering comprises subjecting said mixture to a pressureless sintering process that comprises:
heating said mixture to a peak temperature ranging from 1580 to 1750 degrees Celsius for about 10 to about 300 minutes to form said sintered article;
and cooling said sintered article to room temperature.
5. The method of claim 1 , wherein said sintering comprises subjecting said mixture to a spark plasma sintering process that comprises:
heating said mixture in conductive die to a peak temperature in a range of about 1500 to about 1670 degrees Celsius for about 2 to about 30 minutes while a pulsed direct current is applied to said conductive die and about 10 to about 50 megapascals (MPa) of mechanical pressure is applied to said mixture, so as to form said sintered article; and
cooling said sintered article to room temperature.
6. The method of claim 5 , wherein said heating is performed in an atmosphere of nitrogen (N 2 ) gas, forming gas, or a combination thereof, wherein said forming gas comprises about 2 volume % hydrogen (H 2 ) and about 98 volume % nitrogen (N 2 ).
7. The method of claim 1 , wherein:
said mixture includes an amount, X, of said first particles and an amount, Y, of said second particles;
X ranges from about 5 to about 95 volume percent.
8. The method of claim 7 , wherein said first particles are particles of a β-SiAlON and X ranges from about 30 to about 70 volume percent.
9. The method of claim 1 , wherein said first particles have an average particle size (D50) ranging from about 0.5 micron to about 50 microns, and said second particles have an average particle size ranging from about 100 nanometers to about 5 microns.
10. The method of claim 1 , wherein:
said β-SiAlON is of the formula Si 6-z Al z O z N 8-z , where z ranges from greater than 0 to less than or equal to 4.2;
the at least one sintering aid is Y 3 Al 5 O 12 , MgAl 2 O 4 or a combination thereof;
said mixture comprises an amount, X, of said first particles and an amount, Y, of said second particles, wherein X ranges from greater than or equal to about 5 volume percent and X+Y equals wo volume percent; and
said sintering comprises subjecting said mixture to a pressureless sintering process or a spark plasma sintering process.
11. The method of claim 10 , wherein said sintering comprises subjecting said mixture to a pressureless sintering process that comprises:
heating said mixture to a peak temperature ranging from 1580 to 1750 degrees Celsius for about 10 to about 300 minutes to form said sintered article; and
cooling said sintered article to room temperature.
12. The method of claim 10 , wherein said sintering comprises subjecting said mixture to a spark plasma sintering process that comprises:
heating said mixture in a conductive die to a peak temperature in a range of about 1500 to about 1670 degrees Celsius for about 2 to about 30 minutes while a pulsed direct current is applied to said conductive die and about 10 to about 50 megapascals (MPa) of mechanical pressure is applied to said mixture, so as to form said sintered article; and
cooling said sintered article to room temperature.
13. The method of claim 1 , wherein said mixture contains at least 30% by volume of said second particles.
14. The method of claim 1 , wherein the light source is a light emitting diode (LED).
15. The method of claim 14 , wherein the sintered article is provided as the wavelength converter directly on a light exit surface of the LED, and wherein the LED is configured to emit the primary light at the light exit surface for at least partial conversion into the secondary light by the sintered article.
16. The method of claim 14 , wherein the LED is an indium gallium nitride (InGaN) LED.