Efficient red fluorescent powder without thermal quenching and preparation method thereof
Technical Field
The invention belongs to the field of luminescent materials, and particularly relates to efficient red fluorescent powder without thermal quenching and a preparation method thereof.
Background
The current white light LED realization scheme mainly adopts YAG to Ce3+The yellow fluorescent powder is coated on a blue light chip to realize a bright white light LED, however, with the popularization of the white light LED, the white light LED is found to have low color rendering index, higher color temperature and luminescent property due to the lack of red components, so that the application range of the white light LED is limited. Therefore, researchers at home and abroad develop a three-primary-color scheme, namely near ultraviolet (NUV, 370-410 nm) chips are utilized to combine RGB three-primary-color (red, green and blue) fluorescent powder, and the scheme has the advantages of high excitation energy, high brightness, high light efficiency, stable color and wide fluorescent powder selectivity and is obvious. However, compared with the mature blue powder and green powder, the red powder is still relatively deficient, so that the research on the red fluorescent powder with excellent luminescence performance becomes a hotspot.
Eu3+Ions are important rare earth ions, and because of their special electron shell structure, they have relatively stable emission color, and are widely used in research and development of red phosphors. To increase Eu3+The absorption efficiency of ions, researchers developed a series of red phosphors with high doping concentration, but after the doping concentration was increased, Eu was added3+The distance between ions is shortened, the interaction is enhanced, and the decrease in luminous efficiency and thermal stability is liable to be caused (ACS Applied Materials and interfaces, 2018, 10(48): 41479-41486, ACS Applied Materials&Interfaces,2016, 8(46): 31772-31782.). Especially, the thermal stability of the fluorescent powder is very important for the performance of modern compact LED devices or high-power LED devices, because the working temperature of the semiconductor devices can reach 150 ℃ or even higher, and the LED devices applied to the fields of deep well exploration, nuclear energy and the like have more strict requirements on the thermal stability of the fluorescent powder, the development of the near ultraviolet excited red fluorescent powder with high brightness, high efficiency and high thermal stability still has great challenges.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide the efficient red fluorescent powder without thermal quenching, which has high brightness, high color purity, wide application range and stable performance, and the preparation method thereof.
In order to solve the technical problems, the technical scheme of the invention is as follows: a high-efficiency red fluorescent powder without thermal quenching is characterized in that: the chemical formula of the red fluorescent powder is La1-xEuxSc3(BO3)4Wherein x is the doping concentration, 0<x≤1。
The chromaticity coordinates of the red fluorescent powder are (0.6649-0.6665, 0.3333-0.3348).
The red fluorescent powder is of a calcium carbonate magnesium stone structure, and La ions in the structure are bonded by [ BO ]3]Trigonal sum [ ScO ]6]And (4) filling octahedron.
The preparation method of the non-thermal quenching efficient red fluorescent powder is characterized by comprising the following steps:
the method comprises the following steps: la, Eu, Sc, B = (1-x) x, 3, 4, wherein 0<x is less than or equal to 1, and La containing lanthanum ions is weighed3+Compound raw material of (1), europium ion Eu3+Compound raw material of (1), scandium ion-containing Sc3+Compound raw material of (2), boron ion B3+Grinding and mixing the compound raw materials to obtain mixed powder;
step two: putting the mixed powder obtained in the first step into an agate mortar for grinding for 30min, uniformly mixing, putting into a dried corundum crucible, and presintering at 900-1100 ℃ for 6-10 h;
step three: and (3) putting the mixed powder subjected to the pre-sintering in the step two into an agate mortar for continuously grinding for 30min, continuously calcining at 1300 ℃ after uniform mixing, keeping the temperature for 6h, cooling along with the furnace to obtain a fluffy block sample with light pink color, and grinding the fluffy block sample to obtain the final red fluorescent powder.
The La containing lanthanum ions3+The compound of (A) is lanthanum oxide containing europium ion Eu3+Is europium oxide and contains scandium ions Sc3+The compound of (a) is scandium oxide, and the boron ion B is contained3+The compound of (a) is boric acid.
Compared with the prior art, the technical scheme of the invention has the advantages that:
(1) the fluorescent powder in the invention is Eu3+Ion substituted La3+Ions, which are substituted in the same valence state and have small size difference, do not generate lattice defects;
(2) luminescence center Eu in the invention3+The ions are positioned in the distorted prism polyhedron without inversion symmetry centers, and the electric dipole transition intensity is higher;
(3) the chromaticity coordinate of the red fluorescent powder is very close to the standard red light coordinate (0.67, 0.33) of NTSC, and the purity of the red light is more than 97 percent;
(4) nearest neighbor Eu in the present invention3+The distance between ions is far, so that high-concentration doping (80%) can be tolerated, and the quantum efficiency of 88.3% can be displayed on the basis of the doping;
(5) the red fluorescent powder has ultrahigh heat quenching resistance, and the brightness is not attenuated even at the temperature of 300 ℃;
(6) the red fluorescent powder, the commercial blue fluorescent powder and the commercial green fluorescent powder can be combined to package a high-quality white light LED, the color rendering index Ra of the white light LED is as high as 92.5, and the color temperature CCT of the white light LED is as low as 3438K.
The high-brightness borate red fluorescent powder LaSc prepared by the invention3(BO3)4:Eu3+The preparation method is simple, environment-friendly and pollution-free, and is easy for industrial production, so that the preparation method has wide market prospect.
Drawings
FIG. 1 shows LaSc of a red phosphor sample in example 13(BO3)4:Eu3+The crystal structure of (a);
FIG. 2 shows LaSc of a red phosphor sample in example 13(BO3)4:Eu3+comprises β -LaSc3(BO3)4A standard X-ray diffraction pattern (ICSD No. 89013);
FIG. 3 shows LaSc of a red phosphor sample in example 13(BO3)4:Eu3+And commercial red phosphor CaAlSiN3:Eu2+The excitation spectrum of (1);
FIG. 4 shows LaSc of a red phosphor sample in example 13(BO3)4:Eu3+And commercial red phosphor CaAlSiN3:Eu2+The emission spectrum of (a);
FIG. 5 shows LaSc of a red phosphor sample in example 13(BO3)4:Eu3+The quantum efficiency test spectrogram;
FIG. 6 shows LaSc of a red phosphor sample in example 13(BO3)4:Eu3+A change in luminous intensity in the range of 0-300 ℃;
FIG. 7 shows LaSc of a red phosphor sample in example 13(BO3)4:Eu3+And commercial blue phosphor BaMgAl10O17:Eu2+And green phosphor (Ca, Sr)2SiO4:Eu2+An electroluminescence spectrogram of the warm white light LED constructed by combining the 395 nm near ultraviolet LED chip;
FIG. 8 is the XRD structure refinement pattern of the red phosphor sample in example 3, the refinement templates respectively adopt α -LaSc3(BO3)4(ICSD No. 83404) and β -LaSc3(BO3)4(ICSD No. 89013), and the refinement software was GSAS.
Detailed Description
To further illustrate the technical means and effects of the present invention for achieving the predetermined objects, the following detailed description of the specific embodiments, methods, steps, features and effects of the non-thermal quenching efficient red phosphor and the preparation method thereof according to the present invention with reference to the preferred embodiments is as follows:
example 1:
according to the chemical formula La0.2Eu0.8Sc3(BO3)4Respectively weighing 0.0977g of lanthanum oxide, 0.4223g of europium oxide, 0.6206g of scandium oxide and 0.7643g of boric acid according to the stoichiometric ratio of each element, and putting the weighed raw materials into an agate mortar for grinding for 0.5 hour to obtain the mixtureUniformly mixing, putting the obtained mixture into a dried corundum crucible, putting the crucible into a muffle furnace, pre-burning at 1100 ℃, preserving heat for 6 hours, grinding and uniformly mixing the pre-burned mixture, continuously calcining at 1300 ℃, preserving heat for 6 hours, naturally cooling with the furnace to obtain a light pink blocky product, grinding the blocky product to obtain the final La blocky product0.2Eu0.8Sc3(BO3)4the chromaticity coordinate of the red phosphor is (0.6661, 0.3336), and the X-ray diffraction analysis of the red phosphor shows that the crystal phase is mainly β -LaSc3(BO3)4The structural phase (as shown in figure 2), the fluorescence spectrometer detection result shows that the excitation intensity and the emission intensity are far greater than those of the commercial nitride red fluorescent powder CaAlSiN3:Eu2+(as shown in FIGS. 3 and 4), and the emission spectrum is narrower, the quantum yield is up to 88.3% (as shown in FIG. 5), and the fluorescent powder has ultrahigh thermal stability, and the luminescence does not fade (as shown in FIG. 6) even under the severe environment of 300 ℃, and is similar to the commercial blue fluorescent powder BaMgAl10O17:Eu2+And green phosphor (Ca, Sr)2SiO4:Eu2+The warm white LED device constructed in combination with the 395 nm near ultraviolet LED chip exhibits the advantages of high color rendering index and low color temperature (as shown in FIG. 7).
Example 2:
according to the chemical formula La0.4Eu0.6Sc3(BO3)4Respectively weighing 0.1955g of lanthanum oxide, 0.3167g of europium oxide, 0.6206g of scandium oxide and 0.7643g of boric acid according to the stoichiometric ratio of the elements, putting the weighed raw materials into an agate mortar for grinding for 0.5 hour to obtain a uniform mixture, putting the obtained mixture into a dry corundum crucible, putting the crucible into a muffle furnace, presintering at 1000 ℃, preserving heat for 8 hours, grinding and uniformly mixing the presintered mixture, continuously calcining at 1300 ℃, preserving heat for 6 hours, naturally cooling along with the furnace to obtain a light pink blocky product, grinding the blocky product to obtain the final La blocky product0.4Eu0.6Sc3(BO3)4And (4) red fluorescent powder. The chromaticity coordinate of the red phosphor is (0.6662, 0.3335), and the red phosphor is detectedthe crystal phase is mainly β -LaSc3(BO3)4The structure is similar to that of example 1.
Example 3:
according to the chemical formula EuSc3(BO3)40.5279g of europium oxide, 0.6206g of scandium oxide and 0.7643g of boric acid are respectively weighed according to the stoichiometric ratio of each element in the formula; putting the weighed raw materials into an agate mortar for grinding for 0.5 hour to obtain a uniform mixture, putting the obtained mixture into a dry corundum crucible, putting the crucible into a muffle furnace, presintering at 900 ℃, preserving heat for 10 hours, grinding and uniformly mixing the presintered mixture, continuously calcining at 1300 ℃, preserving heat for 6 hours, naturally cooling along with the furnace to obtain a light pink blocky product, grinding the blocky product to obtain the final EuSc3(BO3)4the chromaticity coordinate of the red phosphor is (0.6663, 0.3335), and the detected crystal phase of the red phosphor is mainly α -LaSc3(BO3)4structural phase sum β -LaSc3(BO3)4the emission spectrum shape was similar to that of example 1 with the mixed phases of the structural phases having alpha and β phases contents of 13.54% and 86.46%, respectively (as shown in fig. 8).