RU2474009C2 - Inorganic luminescent material for solid-state sources of white light - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention relates to the field of lighting technology on the basis of blue-glowing light diodes InGaN, in particular, to luminescent materials, including ittrium oxide, oxides of rare-earth metals, and also aluminium oxide taken in the ratio providing for production of a light-emitting composition, the average structure of which corresponds to the common formula (Y_1-x-yCe_xΣLn_y)_3+αAl₅O_12+1,5α, where _α - value that characterises rise of stoichiometric index in comparison with the one available for ittrium-gadolinium garnet and varying in the range from 0.033 to 2; x - atomic share of cerium equal to 0.001-0.1; ΣLn_y = one or several lanthanides from the group of Gd, Tb, La, Yb, the atomic share of which in the ittrium sublattice makes, accordingly: 0.01 <Gd<0.70; 0.001<Tb<0.2; 0.001<La<0.1; 0.001<Yb<0.1, at the same time for all compositions the difference is [1-x-y]>0.

EFFECT: expanded assortment of inorganic luminescent materials for solid-state sources of white light.

3 cl, 1 tbl, 7 ex

Description

The invention relates to the field of lighting engineering and, in particular, to luminescent materials luminous when excited by blue light in the yellow-orange region of the spectrum and used in solid-state white light sources in which an intense white glow is obtained as a result of a combination of yellow-orange luminescence of a phosphor with primary blue radiation generated by an InGaN LED emitting in the blue region of the spectrum (440-480 nm). In recent years, these devices have been used to create highly efficient white light sources with a light output of up to 150 lumens / watt, which is more than 10 times higher than the light output of incandescent lamps and almost twice as much as the light output of gas-discharge fluorescent light sources. By all accounts, the development of solid-state white light sources is currently determining the prospects for the development of lighting technology.

, где Ln=Gd, Се и совместно с ними один или несколько элементов из группы лантаноидов; Me³⁺ - алюминий или совместно с ним один или несколько элементов из группы Ga, In, Sc. При этом соотношение между

жестко фиксировано и равно

.The effectiveness of devices of this type largely depends on the chemical composition of the phosphors used, which can be used as silicate, phosphate, oxide, aluminate, nitride and oxo-nitride phosphors and their mixtures [C.Ronda. Luminescence: From Theory to Application. Science. 2007, 260 p.]. The most effective among them are aluminate phosphors with a garnet structure, formed with the participation of oxides of yttrium, gadolinium, and other rare earth elements, activated by cerium, denoted in the literature - YAG: Ce. The chemical composition of these phosphors corresponds to the stoichiometric formula

where Ln = Gd, Ce, and together with them one or more elements from the group of lanthanides; Me ³⁺ - aluminum or together with it one or more elements from the group Ga, In, Sc. Moreover, the ratio between

rigidly fixed and equal

.

The key role in the formation of the luminescent properties of yttrium-aluminum garnets along with structure-forming elements is performed by:

Ce, which is an activator of luminescence, i.e. atom, the optical transitions in which determine the color of the glow, and the concentration determines the brightness of the luminescence (related, but correcting functions can perform Pr, Yb);

Gd, Tb, and Lu provide a shift in the position of the maximum in the luminescence spectrum to the long-wave (Gd, Tb) or short-wave (Lu) spectral regions (Ga, In, Sc can play a similar role);

Nd, Eu, Dy, Er, Ho, Tm play an auxiliary role, which was noted in a number of patents, but was not characterized at a quantitative level.

The optical parameters of phosphors for solid-state light sources based on blue-emitting diodes are customarily characterized using the following basic values:

- the maximum in the luminescence spectrum (520-590 nm);

- the half-width of the emission band is 110-125 nm;

- color temperature (T _c ), usually varying in the range of 2500-7000 K (if this parameter is less than 4000 K, the radiation is called “warm white”, if T _c = 4000-5500 K, then the radiation is considered “standard white”, and finally, at Tc> 5500 K - cold white);

- color coordinates (x and y);

- color rendering index;

- the brightness of the glow, usually estimated in comparison with the standard (most often in comparison with samples manufactured by Nichia).

A broadband phosphor with a yellow-orange glow based on yttrium-aluminum garnet activated by cerium (Y, Ce) ₃ Al ₅ O ₁₂ , and the method for its preparation was first patented in 1967 by Philips employees G. Blasse ) and A. Bril (A.Brile) in a number of countries, including the USA: Pat. US 3564322 (US Class: 313/468; Intern'l Class: C09K 11/77) 04/29/1967. A more complex composition (Y, Gd, Ce) ₃ Al ₅ O ₁₂ , with similar luminescent properties, was described in the 70s of the last century, and links to it can be found in the fundamental reference books on luminescent materials [G.Blasse and B. FROM. Grabmaier, "Luminescent materials", Springer-Verlag, Berlin (1994); S. Shionoya. Phosphor Handbook / Science, (1998), 921 pp.].

30 years after J. Blasse in the period from 1998 to 2008. The Japanese company Nichia obtained a series of patents for a device consisting of an InGaN semiconductor heterojunction emitting light with a wavelength of 450-470 nm and coated with grains of a fluorescent substance with a structure of yttrium-aluminum garnet activated by cerium [US Patents No.№ 5998925 (US Class: 313/503; Intern'l Class: H01J 001/62) from 12/07/1997, 6069440 (US Class: 313 / 486,489; Intern'l Class: H01L 033/00) from 05/30/2000, 6608332 (US Class: 257/98) from 08.19.2003, 6614179 (US Class: 353/512; Intern'l Class: H01L 33/00) from 08.19.2003, 7362048 (US Class: 313/512)].

In all of these patents, the authors consider the use of a composition whose composition corresponds to the formula:

, где в числе основных редкоземельных элементов упоминаются иттрий, гадолиний и церий и наряду с ними Lu, Sm, La, Sc.

, where yttrium, gadolinium, and cerium are mentioned among the main rare-earth elements, along with Lu, Sm, La, Sc.

After the first Japanese patent, a number of patent solutions appear in the literature, in which new compositions were proposed, with a modified recipe for the yttrium sublattice of the classic garnet composition with stoichiometric composition in relation to a set of rare-earth elements while maintaining the generalized formula “A ₃ -B ₅ -O ₁₂ ”. For example, for terbium-lutetium garnet, the authors of US Pat. No. 6630077 (US Class: 313/468; Intern'l Class: C09K 11/27 of 10/07/2003) included in the list of claimed lanthanides all 14 f-elements, with their division by type of functional action into structure-forming (Tb, Lu, La , Gd, Yb), activating (Ce) and performing auxiliary functions (Pr, Nd, Sm, Eu, Dy, Ho, Er, Tm).

The most recent patent documents for yttrium-aluminum garnet include US 20080116422 (US Class: 252 / 301.4R; Intern'l Class: C09K 11/08) dated 05/22/2008 and US 20080290355 (US Class: 257/94; Intern'l Class: C09K 11/08) from 11/27/2008. In the first of them, a composition is proposed whose formula is [Y _1-xyzpq Gd _x Tb _y Yb _z Lu _p Ce _q ] ₃ Al ₅ O ₁₂ , in addition to Gd, Ce, Lu, Sm Tb, Yb were added. In the application US No. 2008290355 by the same authors, the phosphor composition is given by the formula [Y _1-xyzq Gd _x Lu _y Yb _z Eu _q + activating additives Ce, Pr, Dy, Er, Sm] ₃ Al ₅ O ₁₂ , where lanthanides were included in the group 9 out of 14 f-elements.

As a new direction in the technology of phosphors for blue LEDs with the participation of yttrium-gadolinium garnet, one can consider the synthesis of compositions whose composition was changed in comparison with the known one by introducing previously undeclared substituents at positions “A” and at positions “B”. The basis for this search was information on the structural features of garnet minerals. In mineralogy, the term garnet is understood to mean more than 10 minerals having the same crystalline structure, but different chemical composition. In particular, the minerals Mg ₃ Al ₃ Si ₃ O ₁₂ , Ca ₃ Al ₂ Si ₃ O ₁₂ , Mn ₃ Al ₂ Si ₃ O _{12 are} well known. In the general case, the formula of minerals having a garnet structure is written as A ₃ B ₂ (BO ₄ ) ₃ = A ₃ B ₅ O ₁₂ . Type A ions, which may include lanthanides, calcium, magnesium, manganese, iron, etc., have a dodecahedral coordination [coordination number (r.h.) equal to 8]. Type B ions (silicon and partially aluminum) have tetrahedral coordination (c.h. = 4). Some of the aluminum ions surrounded by oxygen have octahedral coordination (c.h. = 6).

на

и

), что соответствует формуле:Given this information, in the application US 20070272899 (US Class: 252 / 301.4F; Intern'l Class: C09K 11 / 08.77) dated 11/29/2007 a garnet structure was proposed with the replacement of aluminum by magnesium and silicon (2 ions

on

and

), which corresponds to the formula:

[(YGd + activating additives Ce and / or Cr)] ₃ [Al _5-2x (Mg, Si) _x ] O ₁₂ .

In the application US 20070278451 (US Class: 252 / 301.4R; Intern'l Class: C09K 11 / 08.77) dated 12/06/2007 a two-phase composition [BaAl ₂ O ₄ ] _α + [(Y + Ce, Pr, Eu, Dy, Tb, Mn, Ti / Fe) ₃ Al ₅ O ₁₂ ] _β , in which, according to the authors, the formation of solid solutions is possible. Structural studies have shown that with an “α” phase content of up to 20%, the samples have a cubic structure, while at higher contents, an unsystematic change in the type of crystal structure is observed. The data on the optical properties do not contain data establishing the relationship between the composition of the phosphor and the lighting parameters. Judging by the luminescence spectra shown for the two samples, the phosphors had a sufficiently high brightness and a cool white color, corresponding to 5100 and 6800 K.

The development of this patent solution is the patent application US 20080246005 ((US Class: 252 / 301.4R; Intern'l Class: C09K 11/77) dated 10.10.2008, the authors of which proposed to use solid solutions formed by yttrium as phosphors for blue LEDs aluminum garnet [(Y + Gd, Lu, Ce, Yb, Pr, Sm) ₃ Al ₅ O ₁₂ ] _1-x and garnet composition {[Mg (and / or Ca, Sr, Ba)] ₃ [In (Ga, Sc)] ₂ Si ₃ O ₁₂ } _x . Formally, the proposed composition coincides with that proposed in patent application US 20070272899 (11.29.2007) and is a mixed yttrium-aluminum-silicon garnet with partial replacement of two Al atoms ( In, Ga, Sc) to Mg (Ca, Sr, Ba). The degree of substitution (x) did not exceed a concentration of 15%.

An analogue of the invention is the application US 20090153027 (US Class: 313/503; Intern'l Class: C09K 11/78) dated 06/19/2009, in which a phosphor having the composition [Y _2-xyzq Gd _x Ce _y Pr _z Dy _p O ₃ ] _{1.5 ± .α} + (Al ₂ O ₃ ) _{2.5 ± β} . The purpose of the patent was to obtain warm white radiation through the use of a phosphor, the emission spectrum of which was shifted to the red region as a result of the introduction of three activators, namely cerium, praseodymium and dysprosium. In the description, the authors do not even mention that the achievement of the task may be favored by changing the ratio between the sum of the elements forming the yttrium and aluminum phosphor subsystems. According to the authors, in the framework of the patented composition [atomic fraction by Gd (0.001-0.4), Ce (0.01-0.2), Pr (0.0001-0.1), Dy (0.0001-0 , 1), as well as α (0.01-0.1) and β (0.01-0.1)], it is possible to change the color coordinates in the intervals x = 0.405-0.515; y = 0.355-0.550 at a color temperature of 4000 K and a dominant wavelength in the spectrum of 565 nm. The achieved effect from the use of three activators can be considered as quite trivial (see the table with the characteristics of the phosphors we prepared).

равна 3,02.At the same time, it remains completely unclear what role in solving the problem posed by the authors is played by index variations for the sum of lanthanides and aluminum. It is all the more strange that the characteristics of the emitting system are given for a single (out of many possible) compositions: [Y _2.66 Gd _0.32 Ce _0.03 Pr _0.005 Dy _0.005 ] Al _5.02 O _12.06 , where the sum of the elements

equal to 3.02.

Without any reasoning, the authors initially noted that the index for aluminum (β) should not exceed “5” (“to increase the quantum efficiency of the phosphor according to the present invention, the anionic oxide fraction should not exceed 5.0 units”) . But the three lines below write that at the index α = 0, an increase in the index β by 0.01 increases the quantum efficiency by about 1% (while it remains unclear, firstly, how it was measured, and secondly, by what methods was provided such accuracy). On the other hand, the authors note that a decrease in the index α will lead to a narrowing of the spectrum, i.e. reducing the half-width of the luminescence band. The scale of the impact on this parameter is characterized by a value of 0.5-0.8 nm for every 0.005 units of the index "α". The maximum shift according to the observations of the authors was from 118 to 115 nm. This means that the maximum variation of the α index in the samples studied by the authors was 0.03. According to the authors, the preferred index values are 0.01 for "α" and 0.03 for "β" ("according to the preffered embodiment of the present invention, the stable stoichiometric index" α "is ... 0.01., The second index "β", whose increment cannot exceed 0.03 mole fraction ").

Given this conclusion, and also taking into account the lack of quantitative information about the effect of indices on the lighting parameters of phosphors, there is a natural doubt about the validity of including in the patented patent application the invention of the upper values of both indices equal to 0.1.

It should be emphasized that the indices designated by the authors as preferred almost coincide with those indicated in the US Pat. No. 7135129 (U.S. Class: 252 / 301.4R; Intern'l Class: C09K 11/08) dated 11/14/2006.

This patent is the closest in technical essence to our invention. The authors declared a phosphor of the composition: [(Y _1-xyzq Gd _x Dy _y Yb _z Er _q Се _p )] _α (Al _1-nmk Ga _n Sc _k In _l ) _β O ₁₂ , whose stoichiometric indices were α = 2.97 -3.02 and β = 4.98-5.02. They differed from the traditional ones in the structure of stoichiometric yttrium-aluminum garnet, components 3 and 5. Among the known patent solutions related to phosphors based on the classic yttrium-aluminum garnet, the authors first proposed the synthesis of non-stoichiometric garnet, although indicated in a very narrow composition range (± 0.02).

The luminescent material was obtained as a result of a three-stage heat treatment of a mixture of hydroxides Gd, Y, Ce, Dy, Er, Yb, Al and Ga, coprecipitated by ammonia from a solution of mixtures of nitrates of these metals. The precursors were calcined in the presence of mineralizers in a hydrogen medium: first, at 500 K, then 900-1100 K, and finally, at 1400-1700 K, followed by gradual cooling to 400 K. The resulting product was strongly sintered after heat treatment, and it was ground to a particle size <1.5 μm. Grinding to such a small size should inevitably lead to some decrease in the brightness and quality of the phosphor.

The maximum in the emission spectrum of the claimed luminescent material, when excited by a blue LED, varied depending on the composition from 535 to 590 nm. The white radiation generated by mixing the yellow-orange luminescence of the phosphor with the blue color of the LED had a color temperature of 3000 to 16000 K.

The objective of the invention is to expand the range of inorganic luminescent materials for solid-state white light sources.

,The problem is solved by creating an inorganic luminescent material for solid-state white light sources based on blue-emitting InGaN LEDs, including yttrium oxide, rare-earth metal oxides, and aluminum oxide, while the composition of the inorganic luminescent material corresponds to the general formula

,

where α is a value characterizing the increase in the stoichiometric index in comparison with the known for yttrium-gadolinium garnet and varying in the range from 0.033 to 2;

x is the atomic fraction of cerium, equal to 0.001-0.1;

- один или несколько лантаноидов из группы Gd, Tb, La, Yb, образующих совместно с иттрием и церием иттриевую подрешетку.

- one or more lanthanides from the group Gd, Tb, La, Yb, which together with yttrium and cerium form an yttrium sublattice.

Along with these elements, Pr, Nd, Sm, Eu, Dy, Er, Lu can be included in its composition.

включает кроме иттрия и церия (x) также гадолиний (Gd_p), тербий (Tb_q), лантан (La)_r и иттербий (Yb)_s при этом у=1-х=p+q+r+s, где p - атомная доля гадолиния, равная 0,01-0,70; q - атомная доля тербия, равная 0,001-0,2; r, s - атомные доли лантана и иттербия, равные 0,001-0,1.In the case of the proposed inorganic luminescent material, its yttrium sublattice

in addition to yttrium and cerium (x), also gadolinium (Gd _p ), terbium (Tb _q ), lanthanum (La) _r and ytterbium (Yb) _s with y = 1-x = p + q + r + s, where p - the atomic fraction of gadolinium equal to 0.01-0.70; q is the atomic fraction of terbium, equal to 0.001-0.2; r, s are the atomic fractions of lanthanum and ytterbium equal to 0.001-0.1.

For values of the stoichiometric index (3 + α) varying from 3.034 to 3.45, the proposed material is a phase of a cubic structure, the lighting characteristics of which for a given composition of rare-earth elements weakly depend on the value of the stoichiometric index, while for a given stoichiometric index, the variation in cationic composition can lead to a change in color coordinates and the position of the maximum in the luminescence spectrum in the range from 550 to 590 nm, which allows you to change the color temperature of the solid state second source of white light from 2700 to 4500 K.

от 3,45 до 5 предлагаемый люминесцирующий материал представляет собой смешанную композицию из двух фаз, одна из которых имеет кубическую структуру и состав

, а другая является модификацией алюмината иттрия состава

, допированного Gd, Tb, La, Yb и активированного церием, причем при заданном катионном составе светотехнические параметры двухфазных композиций зависят от величины индекса (3+α) вследствие увеличения относительного содержания орторомбической модификации алюмината иттрия, так что цветовая температура твердотельного источника белого света может в зависимости от состава изменяться от 3000 до 6000 К.In the range of indices y

from 3.45 to 5, the proposed luminescent material is a mixed composition of two phases, one of which has a cubic structure and composition

and the other is a modification of the yttrium aluminate composition

doped with Gd, Tb, La, Yb and activated by cerium, and at a given cationic composition, the lighting parameters of two-phase compositions depend on the index value (3 + α) due to an increase in the relative content of the orthorhombic modification of yttrium aluminate, so that the color temperature of a solid-state white light source can depending on the composition vary from 3000 to 6000 K.

, близки или совпадают с параметрами промышленных и синтезированных нами образцов традиционного иттрий-алюминиевого граната при вариации α в пределах 0,03<α<2 (см. таблицу). Нижняя граница указанного интервала (α=0,033) отвечает пределу, обозначенному в прототипе, тогда как верхняя отвечает формуле

, т.е. соединению, в котором соотношение

.Our studies have shown that the lighting characteristics of the compositions, the composition of which corresponds to the General formula

are close or coincide with the parameters of industrial and synthesized by us samples of traditional yttrium-aluminum garnet with α variation within 0.03 <α <2 (see table). The lower boundary of the specified interval (α = 0,033) corresponds to the limit indicated in the prototype, while the upper corresponds to the formula

, i.e. a compound in which the ratio

.

Case Studies

Phosphors, the composition of which is given in the list of examples, were obtained by heat treatment of a mixture of oxides of yttrium, cerium, gadolinium, terbium, lanthanum, ytterbium and aluminum hydroxide (or a mixture of hydroxides, coprecipitated from aqueous solutions of nitrates). The prepared mixtures were calcined in the presence of mineralizers (fluxes), contributing to an increase in the mass transfer rate due to the formation of a liquid phase on the surface of reacting solids, and thereby leading to an increase in the rate of formation of the target product by reactions:

or

where an increase in the amount of water to x / 2 where x - number of moles of CeO ₂ in the initial mixture of oxides due to the reduction in hydrogen of CeO ₂ to Ce ₂ O _3.

Mixtures of barium chloride and fluoride (up to 7-10% by weight of oxides), as well as aluminum and ammonium fluorides (<1%) in the presence of small amounts of boric acid (<0.5%) were used as fluxes.

The starting materials (lanthanide oxides and aluminum hydroxide) with a known particle size distribution (laser particle size analyzer) were mixed dry on a vibrating stand or in a drunken barrel type mixer in closed polyethylene vessels using polyethylene-coated metal balls. Calcination was carried out in alundum crucibles (Al ₂ O ₃ ) with gradual heating of the reactants in a reducing medium (N ₂ + H ₂ ) at a speed of 7-10 deg / min to a temperature of 1350-1450 ° C. The exposure time at high temperature was 3-5 hours, after which the crucibles were cooled to 400 ° C for 2.5 hours.

была >3,1, то дополнительное измельчение не было необходимым и при правильно подобранном гранулометрическом составе прекурсоров средний размер частиц люминофора составлял около 3,5-5,0 мк.A study of the prepared phosphors showed that the samples, whose composition corresponded to a stoichiometric garnet, sintered quite strongly and required additional grinding. If the value of the index y

was> 3.1, then additional grinding was not necessary, and with the correctly selected particle size distribution of the precursors, the average particle size of the phosphor was about 3.5-5.0 microns.

To remove the melt, the prepared samples were washed several times with a large volume of distilled water and dried in an oven at 150 ° C.

Example No. 1:

The synthesis of the sample composition (Y _0.847 Gd _0.129 Ce _0.024 ) _3.00 Al ₅ O ₁₂ was carried out using Y ₂ O ₃ , Gd ₂ O ₃ , CeO _2, and Al (OH) ₃ as starting materials. Annealing temperature 1400ºС. Duration of exposure at high temperature 3.5 hours.

Example No. 2:

Synthesis of sample composition (Y _0.851 Gd _0.127 Ce _0.022 ) _3.03 Al ₅ O _12.045 . The starting materials were coprecipitated hydroxides. Annealing temperature 1350ºС. Duration of exposure at high temperature for 3 hours.

Example 3:

The synthesis of the sample composition (Y _0.864 Gd _0.115 Ce _0.021 ) _3.34 Al ₅ O _12.465 was carried out using Y ₂ O ₃ , Gd ₂ O ₃ , CeO ₂ and Al (OH) ₃ as starting materials. Annealing temperature 1400ºС. Duration of exposure at high temperature 3.5 hours.

Example 4:

The synthesis of the sample composition (Y _0.555 Gd _0.4 La _0.005 Ce _0.04 ) _3.5 Al ₅ O _12.75 was performed using Y ₂ O ₃ , Gd ₂ O ₃ , La ₂ O ₃ , CeO as starting materials ₂ and Al (OH) ₃ . Annealing temperature 1450ºС. Duration of exposure at high temperature for 4 hours.

Example No. 5:

The synthesis of the sample composition (Y _0.95 Gd _0.01 Ce _0.04 ) _3.5 Al ₅ O _12.75 was carried out using Y ₂ O ₃ , Gd ₂ O ₃ , CeO ₂ and Al (OH) as starting materials ₃ . Annealing temperature 1450ºС. Duration of exposure at high temperature for 4 hours.

Example 6:

The synthesis of the sample composition (Y _0.955 Yb _0.005 Ce _0.04 ) _4.00 Al ₅ O _13.5 was carried out using Y ₂ O ₃ , Yb ₂ O ₃ , CeO ₂ and Al (OH) ₃ as starting materials. Annealing temperature 1450ºС. Duration of exposure at high temperature for 4 hours.

Example No. 7:

For the synthesis of a sample of the composition (Y _0.95 Tb _0.01 Ce _0.04 ) _5.00 Al ₅ O ₁₅ , Y ₂ O ₃ , Tb ₄ O ₇ , CeO _2, and Al (OH) ₃ were used as starting materials. Annealing temperature 1450ºС. Duration of exposure at high temperature for 5 hours.

Lighting parameters of samples No. 1-7 were measured in certified installations by two methods. In the first of them, the spectra of the white radiation spectrum were recorded when blue radiation was reflected from the synthesized phosphor powders with a yellow-orange glow. Using the second technique, the spectra were measured after blue radiation passed through a solid organic matrix with a dispersed phosphor, i.e. in conditions simulating the operation of white lamps based on blue-emitting diodes (white LED lamp). The results of spectral measurements by the second method are shown in table No. 1 in italics. For comparison, the data on the lighting characteristics of industrial samples of phosphors manufactured by Nichiya are also presented there.

от 3 до 3,4-3,5 существует фаза с кубической структурой, гомогенность которой не нарушается несмотря на значительное отклонение индекса от величины, определяющей границу классического граната А₃В₅O₁₂, в случае которого индекс «3» считается жестко фиксированным.X-ray phase analysis of the samples showed that in the range of the index y

from 3 to 3.4-3.5 there is a phase with a cubic structure, the homogeneity of which is not violated despite a significant deviation of the index from the value determining the boundary of the classic garnet A ₃ B ₅ O ₁₂ , in which case the index "3" is considered to be rigidly fixed.

An analysis of the literature on the crystalline structure of another compound between yttrium-aluminum and oxygen, namely YAlO ₃ (Y ₅ Al ₅ O ₁₅ ), showed that this substance, depending on the preparation conditions, may have an orthorhombic, hexagonal and cubic structure [S. Mathur , H. Shen ao: J. of Material Chemistry. 2004]. Moreover, the lattice parameters of the cubic phase (Selected Powder Diffraction Data, JCPDS, file 38-0222) and diffraction reflections over the entire set of hkl indices coincide with Y ₃ Al ₅ O ₁₂ , despite a significant difference in the ratio between yttrium and aluminum.

, состав которой отвечает вариации индекса от 3 до 3,45, можно рассматривать как гомогенный твердый раствор кубического алюмината иттрия Y₅Al₅O₁₅ в фазе допированного лантаноидами иттрий-алюминиевого граната. Учитывая подобие структур и совпадение параметров решетки, вариация индекса (при заданных концентрациях церия и составе иттриевой подрешетки), а также связанное с ней изменение соотношения

не приводят к ощутимому изменению яркости желто-оранжевой полосы, положения максимума в спектре люминесценции, цветовых координат и цветовой температуры (см. таблицу экспериментальных данных).Thus the non-stoichiometric phase

, whose composition corresponds to index variations from 3 to 3.45, can be considered as a homogeneous solid solution of cubic yttrium aluminate Y ₅ Al ₅ O ₁₅ in the phase of yttrium aluminum garnet doped with lanthanides. Given the similarity of the structures and the coincidence of the lattice parameters, the variation of the index (for given cerium concentrations and the composition of the yttrium sublattice), as well as the related change in the ratio

do not lead to a noticeable change in the brightness of the yellow-orange strip, the position of the maximum in the luminescence spectrum, color coordinates, and color temperature (see table of experimental data).

According to the results of X-ray phase analysis, at indices (3 + α)> 3.5, the system becomes two-phase. The transition to the two-phase region is detected by the appearance of a set of reflections belonging to the orthorhombic modification of YAlO ₃ against the background of diffraction reflections from the cubic phase. The right column of the table contains data on the ratio of the cubic and orthorhombic phases, which was taken to be equal to the ratio of the intensities of 100% reflections from each phase (cubic: d = 2.707, hkl [420]; orthorhomb. D = 2.617, hkl [121]). Sample composition (Y _0,95 Tb _0,01 Ce0, _{04) 5} Al ₅ O ₁₅ was also biphasic in connection with the presence of both orthorhombic and cubic modifications doped yttrium aluminum perovskite.

Upon transition to the two-phase region, an increase in the reflection intensity of blue radiation was observed, increasing with the content of the orthorhombic phase. This is because the reflection coefficient of YAlO _{3 is} greater than that of Y ₃ Al ₅ O ₁₂ (1.95 and 1.82 according to [C. Ronda. Luminescence: From Theory to Application. Science. 2007, 260 pp.]).

When registering the spectrum of the total radiation of a white light source under conditions when blue radiation is reflected from the surface of the phosphor, the ratio of the maxima of the blue and yellow-orange radiation in the sample composition (Y _0.96 Ce _0.04 ) _4.00 Al ₅ O _13.5 was about 3: 1 and reached 6: 1 in the case of (Y _0,95 Tb _{0,01 Ce0, 04) 5} Al ₅ O _15. The consequence of this was an increase in the color temperature from 4278 to 15000 K. If the blue radiation passes through a polymer organic matrix with a suspended phosphor forming the shell of a lamp with a blue LED (white LED lamp), then changing the thickness of the absorbing layer or the concentration of the phosphor in the photoconverting and scattering medium it is possible to almost completely “utilize” blue radiation and lower the color temperature of white radiation to 4500-6000 K even for a sample of composition (Y _0.96 Tb _0.01 Ce _0.04 ) _5.00 Al ₅ O ₁₅ . Moreover, the luminescence brightness in the range of indices from 3.5 to 4.5 decreased by less than <20-25% in comparison with the cubic phase.

от 0,604 до 1 обладают светотехническими свойствами, вполне сопоставимыми с характеристиками образцов, состав которых отвечает стехиометрическому гранату.Thus, the luminescent compositions in the system (Y-Ln) ₃ Al ₅ O ₁₂ -Y ₅ Al ₅ O ₁₅ despite a significant increase in the ratio of elements

from 0.604 to 1 have lighting properties that are quite comparable with the characteristics of samples whose composition corresponds to a stoichiometric grenade.

Claims (3)

1. Inorganic luminescent material for solid-state white light sources based on InGaN blue-emitting diodes, including yttrium oxide, rare-earth metal oxides, and aluminum oxide, characterized in that the composition of the inorganic luminescent material corresponds to the general formula (Y _1-xy Ce _x ∑ Ln _y ) _{3 + α} Al ₅ O _{12 + 1,5α} , α is a value characterizing an increase in the stoichiometric index in comparison with that known for yttrium-gadolinium garnet and varying in the range from 0.033 to 2;
x is the atomic fraction of cerium, equal to 0.001-0.1;
y is the sum of the atomic fractions (∑Ln _y ) of the lanthanides, which together with yttrium and cerium form the yttrium sublattice, which includes, in addition to yttrium and cerium, gadolinium (Gd _p ), terbium (Tb _q ), lanthanum (La _r ) and ytterbium ( Yb _s ), with y = p + q + r + s, where p is the atomic fraction of gadolinium, equal to 0.01-0.70; q is the atomic fraction of terbium, equal to q = 0.001-0.2; g, s are the atomic fractions of lanthanum and ytterbium equal to 0.001-0.1, and for all compositions the difference is [1-x- (p + q + r + s)] = [1-xy]> 0. 2. The inorganic luminescent material according to claim 1, the stoichiometric index value (3 + α) of which varies from 3.034 to 3.45, which is a phase of a cubic structure, the lighting characteristics of which for a given composition of rare-earth elements weakly depend on the value of the index, then as at a given stoichiometric index, a variation in the cationic composition can lead to a change in color coordinates and the position of the maximum in the luminescence spectrum in the range from 550 to 590 nm, which allows you to change the color temperature solid-state white light source from 2700-4500 K. 3. The inorganic luminescent material according to claim 1, the index value (3 + α) which varies from 3.45 to 5, which is a mixed composition of two phases, one of which has a cubic structure and composition (Y _1-xy Се _x ∑ Ln _y ) _3.45 Al ₅ O _12.67 , and the other is a modification of yttrium aluminate with the composition (Y _1-xy Ce _x ∑ Ln _y ) ₅ Al ₅ O ₁₅ activated by cerium and doped with Gd, Tb, La, Yb, moreover, for a given cationic composition, the lighting parameters of two-phase compositions depend on the index value (3 + α) due to an increase in the relative content of orthorhombi modification of yttrium aluminate, so that the maximum in the luminescence spectrum can vary in the range from 550 to 580 nm, which allows you to change the color temperature of a solid-state white light source from 3000 to 6000 K.