FR2572735A1 - LUMINESCENT MATRIX BASED ON BORATE - Google Patents

Abstract

BORATE-BASED LUMINESCENT MATRIX RESPONDING TO THE GENERAL FORMULA: LA, Y, EU (MG, ZN) BODIN WHICH THE LANTHANE CAN BE REPLACED IN PART OR IN TOTAL BY YTTRIUM AND THE EU, LAY AND MGZN IONS FORM LINEAR ROWS, THE IONS BORATE FORMING BIDIMENSIONAL NETWORKS BETWEEN THEM, IN WHICH THE LAY AND EU IONS ARE COORDINATED WITH 10 ATOMS OF OXYGEN, THE MGZN IONS BEING PLACED IN AN OCTAHEDRA FORMED BY 6 ATOMS OF OXYGEN, THE MATRIX BEING ACTIVATED BY MA ACTIVATORS THE LAY IONS LAY AND BY ACTIVATORS MA THE PLACE OF IONS MGZN, M BEING TB AND POSSIBLY GD, THIS ETOU BI AND M BEING MN OR EU.

Description

The present invention relates to a luminescent material and in particular

  to a luminescent matrix based on borate.

  Until the second half of 1970,

  based on halophosphates in gas discharge lamps.

  Such materials emit in a broad band of yellowish radiation when excited by low pressure mercury vapor lamp radiation. Studies have shown that the light intensity can be increased by using a mixture of three luminescent materials, a mixture containing materials emitting in blue radiation (450 nm),

  green (540 nm) and red (610 nm). These luminescent materials have been prepared

  This emission is based on rare earth metals, the blue emission being based on Eu2 + ions, the green emission based on Tb3 + ions and the green emission based on Eu3 + ions. Luminescent materials containing a mixture of three or more luminescent materials and discharge lamps coated with these

  materials have already been available for some time.

  Thus, it has already been known a discharge lamp provided with a light film

  nescent containing a mixture of luminescent material based on halophos-

  bivalent europium-activated phage, such as the luminescent material emitting

  both the blue radiation, and a halophosphorus-based phosphor

  europium bivalent activated phoborate, a luminescent material emitting green radiation, which contains cerium and terbium coactivated silicon phosphate, and a luminescent material emitting radiation

  red, which contains trivalent europium activated yttrium oxide.

  According to another known technique, the luminescent film used in the discharge tubes contains as a luminescent material emitting in blue a mixture of bivalent europium activated halophosphate or,

  as a luminescent material emitting in the green, a material

  holding a silicon phosphate which has been coactivated by cerium and terbium and, as a luminescent material emitting in the red, a material

  containing yttrium oxide activated by trivalent europium.

  According to another known technique, the luminescent film used in discharge lamps contains, as a blue-emitting material, a divalent europium activated barium and magnesium aluminate, as a material emitting in the green, a cerium aluminate. and terbium-activated magnesium and, as a red-emitting material, a

  trivalent europium activated yttrium oxide.

  However, the use of coatings containing such mixtures of

  several luminescent materials have disadvantages.

  It is difficult to homogeneously mix powders having different physical properties and to form homogeneous layers on

  lamps containing such mixtures.

  The behavior in time of different luminescent materials is variable depending on the materials, ie the color of the lamp changes during its use, while the light intensity of some

luminescent materials decreases.

  Moreover, the quantum efficiency of a mixture of several materials

  The luminescence is never as good as that of a single lumi-

  NESCent. The maximum efficiency of the excitation energy is not obtained, a part of this energy being dissipated by the effect of shadow, of limits

granules and others.

  The object of the present invention is the elimination of such drawbacks by proposing a luminescent material which makes it possible to obtain, with one and the same luminescent material, two or more colorations due to the

  same excitement. By using selective excitation of different energies

  rents, some emissions have already been obtained from certain

  different stains, especially in the activator-sen-

  sibilizer, whose wavelength may be in the range

  visible, but the intensity is usually low. In principle

  However, several emission and absorption ions cause disturbances

  reciprocal bations in luminescent materials. In general,

  impurities greater than a few ppm are not tolerated in

such luminescent materials.

  Thus, another object of the present invention is to provide a luminescent material in which the mutual interaction and disruption of the luminescent ions is minimized so as to be able to obtain

  an emission of several colors.

  The luminescent matrix based on borate according to the invention is characterized in that it corresponds to the general formula La, Y, Eu3 + (MgZn) B5010 in which the lanthanum can be partially or totally replaced

  by yttrium and in which the La / Y, Eu3 + and Mg / Zn ions form

  borate ions forming two-dimensional networks between them

  The La / Y and Eu3 + ions are coordinated with 10 oxygen atoms, the matrix being subsequently activated by M2 + activators housed in place of the Mg / Zn ions and optionally by the M3 + activators housed in place of the La / Y ions, M3 + being Tb3 + and possibly Gd3 +, Ce3 + and / or

Bi3 + and M2 + both Mn2 + or Eu2.

  Bi3 and M2 being Mn2 or Eu Thus, the invention relates to a matrix in which Mg2 + and Zn2 + can be substituted for each other completely in the network without causing the structure to change. In the row La, the distance between

  The ions inside the network are significantly smaller than the

  between the ions belonging to the several rows. Between the

  Borate ions form borate

  dimensional (Bi50105) n. The La ions are coordinated with 10 oxygen atoms which form an irregular coordination polyhedron. Ions

  Mg / Zn are placed in the middle of the elongated octahedron formed by 6 oxy-

  gene. In the luminescent matrix according to the invention, it is possible

  replace the La ion with M3 + activators and the Mg / Zn ion with

  M2 +. It has surprisingly been observed that in a matrix according to the invention there is no decrease due to the concentration,

  which means that the concentrations of the activator are not critical.

  but may vary within wide limits.

  According to the invention, the La ions can be completely replaced

  or partially by trivalent Tb and optionally by Gd, Ce and / or Bi ions.

  In Mg / Zn networks, Mg / Zn can be partially replaced by ions

Mn and Eu bivalents.

  More particularly, the matrix has the general formula Lal.uv.xy. z GduCevBixTbyEuz (MgZn) B501, in which: ## EQU1 ## where: ## EQU1 ## z <0.7

u + x + y + z <1.

  According to another preferred embodiment of the invention, the matrix corresponds to the general formula Laluvxz GduCevBixTbyEuz (MgZn) lrEurB5lo, in which 0 <u <0.955 O <v <l -ux-z 0 <x <0.3 0.005 <z <0.7 x + u + z <1

0.005 <r <0.7.

  According to one variant, the matrix corresponds to the general formula Lal'u'v'xyzGduCevBixTbyEUz (Mg'Zn) lr EurB5010 in which: 0o u <<0, 99 O <v <1 -u -xy-z 0 <x < 0.3 0.005 <z <0.7 ux + + x + y + z <1l

0.005 <r <0.7.

  According to another variant, the matrix corresponds to the general formula ## STR1 ## in which: 0 <u <0.99 v <0.30 <x <lu - vz 0.005 <z <0.7 u + x + z <1

0.01 <p <0.3.

  According to another variant, the matrix corresponds to the general formula: ## STR1 ## in which: 0 <v <l -uxyz 0 <x <0.3 0.005 <y <0.7 0.005 <z <0.7 u + x + y + z <1 0.01 <p 0.3

0.005 <r <0.5.

  In the luminescent matrix, La can be partially or totally replaced by Y. The excitation and emission wavelengths of the following luminescent ions in the La (Mg, Zn) B5010 matrix are as follows:> excitation / nm emission / nm Ce3 + 270 300 Bi3 + 290 330 Gd3 + 277 313 Eu3 + 250 (CTS), 290-410 (4f) 610 (maximum) Tb3 + 200 (4f-5d), 290-390 (4f) 542 Mn2 + 280-380 630 Eu2 + 330 430

  Ions with a broad absorption or emission band can

  come luminescent at slightly different wavelengths according to

the concentration of the activator.

  This table shows that, based on the spectrum, energy transfers

  cerium and bismuth to terbium and europium 4f are pos-

sible.

3+ 3

  It has also been shown experimentally that Ce3 --Gd3 + transfers

  and Bi3 ± -Gd3 + are possible. It is the specific character of gado-

  limium, especially the fact that 313 nm lines can also absorb, which makes possible such transfers. In addition, energy can

  be transferred from gadolinium also to europium and terbium.

  Energy can travel very long distances in the network of

  gadolinium and even jump from one row to another.

  The above only concerns the transfer of energy within networks formed by a trivalent cation. The transfer of energy from a La3 + network to an Mg2 + / Zn2 + network can also be caused to occur with both bismuth and gadolinium. However, the

  cerium transfers its energy very little to a divalent network.

  When the excitation energy reaches a network that contains gadolinium, the transfer of energy occurs rapidly through (the entire network of Gd. At the end of the energy network can meet

  a non-luminescent ion, lanthanum, from which energy can return-

  or jump into the next Gd network. When the excitation energy traveled far enough by encountering only La ions at the end of Gd networks, it finally discharges itself by producing the emission

  characteristic of gadolinium. By browsing through many points of

  bucket, the energy can, of course, also meet an imperfection

  of the network, which causes a discharge of energy without producing radiation.

  If, on the contrary, the energy arriving in a gadolinium network

  against a luminescent ion (Eu3 +, Tb3 +) at the end of the network, it excites

  this ion, which can not transmit further energy but emits energy.

  in the form of light (green, red). As mentioned before,

  the energy present in the gadolinium lattice can also be transferred to an Mg2 lattice and there meets a luminescent ion (Mg2 +,

  Eu2 +) which becomes excited and emits its characteristic light (red, blue).

  The luminescent material according to the invention has gadolinic networks.

  relatively long, which have been interrupted by either lanthanum or a small amount of europium or terbium. Thanks to the structure of La (Mg, Zn) B5010 and at low concentrations of the activator, it is possible to obtain that the Eu and Tb + ions become luminescent independently and no mutual extinction is observed, such as in

other materials.

  Similarly, it is possible to place in a matrix La (Mg, Zn) B5010 at the

  bivalent europium and trivalent europium and to obtain

  nescence in the visible from both. It is a unique known material in which the blue emission of Eu2 + and the red emission of Eu3 + are well perceptible. With the luminescent material according to the invention, it is possible, by selecting the combinations of activators, to obtain green and red emission (Tb3 +, Eu3 + and / or Tb3 +, Mn2 +), blue and red (Eu2 +, Eu3 +) , a very strong red emission (Eu3 +, Mn2 +) or even blue,

2+ 3+ 3+ 2+

  green and red (Eu2 +, Tb3 +, Eu3 + and / or Mn2 +). By varying the concentrations

  activator it is possible to produce different shades of colors. When the luminescent material according to the invention is used in low pressure mercury vapor lamps, only 1 to 2 luminescent materials are needed instead of 3 to 4. The manufacture of lamps is thus simplified and the quantum efficiency is improved. It is possible to produce by means of a compound activated by Eu3 + and Mn2 + a strongly red emission in which the band and the line of the spectrum are above each other. This material is very suitable for the manufacture of the so-called luxury lamps, for which one avoids

good color reproduction.

  The invention will be described hereinafter in detail with the aid of the examples with reference to the accompanying drawings, in which FIG. 1 shows the arrangement of different ions in the ac plane of the matrix La (Mg, Zn) B5010, the figure 2 the arrangement according to the plane ab without indication of the ions oxygen, and figure 3 the arrangement according to the plane bc without indication of the ions

oxygen and boron.

  FIGS. 4 to 7 show the emission spectra of light materials

nescents according to the examples.

  The process for preparing the luminescent material according to the present invention

  vention is within the reach of those skilled in the art. It consists in mixing the ions chosen in the form of compounds, for example oxides, then

  selectively heat them in the reducing atmosphere. Hereinafter

  examples of the preparation of certain luminescent materials

particularly advantageous.

Example 1

  A mixture containing 4.078 g of Gd203 0.421 g of Tb407 0.176 g of Eu203 1.058 g of MgO 9.656 g of H3B03

  is dissolved in 40 cm3 of concentrated nitric acid. The solution is

  dry pored and the residue is ground to form a homogeneous mixture. The

  The mixture is heated in a reducing atmosphere, first at 40 ° C,

  the water and the oxides of nitrogen are released, then for one hour at 700 C and for 3 hours at 950 C. The material is cooled and crushed

  and excess boric acid can be removed by washing with water.

  The emission spectrum of the product (Gdo 9Tboo 9Euoo1) MgB5010 is presented in FIG. 4. The excitation spectrum shows both the band of

3+ 3+ 3+ 3

  Eu3 + and a net peak of Gd3, as well as net peaks of Eu3 + and Tb3 +.

  During preparation, it is recommended to use an excess of boric acid, since a certain amount of this acid evaporates during heating. On the other hand, an excess of boron stimulates the reaction. The product

  reaction can also be milled after each heating step,

  after heating at 4000C and 700C.

Example 2

  The mixture according to Example 1 is mixed in a ball mill to obtain a homogeneous mixture and is heated as indicated in

  Example 1 in a reducing atmosphere.

  No extraction being carried out, it is necessary to carry out an additional grinding and a thermal treatment at 950 C.

Example 3

  A mixture containing 6.682 g of La 2 O 3 3.066 g of Eu 2 O 3 1.704 g of MgO 19, 228 g of H 3 BO 3 is treated according to the preceding examples in a reducing atmosphere and gives

  a composition product (La0.825Eu0.175) (Mg90.825Eu0.175) B5010.

  The excitation spectrum of this material consists of two bands, the CTS band of trivalent europium at 250 nm and the band 4f-5d of bivalent europium at 350 nm. The excitation spectrum of the blue emission of Eu2 + also contains a band at 250 nm which signifies the energy transfer Eu3 + - Eu2 +. The emission spectrum of this material is shown in

figure 5.

Example 4

  A mixture containing 0.021 g of Ce (SO4) 2.4H2O 0.224 g of La203 0.187 g of Gd203 0.010 g of Tb407 0.023 g of Eu203 0.106 g of MgO 0.994 g of H3B03 is treated according to the preceding examples in a reducing atmosphere. The product obtained corresponds to the formula (Lao, 535Gdo, 4Ceo 0.2Tb 0.2Euo 025) (M9o, 975Euo 025) B5010 The emission spectrum of this product contains colors of the three ions

emission (Figure 7).

Example 5

  A mixture containing 3.571 g of La 2 O 3 0.473 g of Gd 2 O 3 0.235 g of Bi 2 (CO 3) 3 0.138 g of Eu 2 O 3 0.150 g of Mn CO 3 1.049 g of MgO, 086 g of H 3 BO 3 is treated according to the preceding examples, but the atmosphere should not necessarily be reductive. The product obtained of formula (Lao, 84Gd0, 10Bi00.3EU0O03) (Mg0.95Mno, 05) B5010 produces a strong red emission, since it contains two activators

  emitting in the field of red (Figure 6).

Example 6

  A mixture containing 1.402 g of Y 2 O 3, 2.252 g of Gd 2 O 3, 1.158 g of CeCl 3. 7 H 2 O 0.546 g of Eu 2 O 3 0.658 g of MgO 1.264 g of ZnO 12.004 g of H3BO3

  is treated according to the previous examples in a reducing atmosphere.

  The product obtained corresponds to the formula (Yo, 4Gdo, 4Cdo, 1Euo, 1) (Zno, 5Mgo, 5). B5010 In this product the activator is terbium, which gives a typical green coloring. Cerium serves as an absorber of ultraviolet light and gadolinium as an intermediate for transmission of energy to terbium.

  Only the spectrum of Eu3 + is in the visible range.

Claims (7)

CLAIMS.   1. Luminescent matrix based on borate, characterized in that it corresponds to the general formula La, Y, Eu3 + (MgZn) B5010 in which the lanthanum can be replaced partially or totally by yttrium and in which the ions La / Y, Eu3 + and Mg / Zn form linear rows, the borate ions forming between them two-dimensional networks, where the La / y and Eu3 + ions are coordinated with 10 oxygen atoms, the Mg / Zn ions being located in an octahedron formed by 6 oxygen atoms, the matrix being subsequently activated   by M2 + activators housed in place of the Mg / Zn ions and possibly   by the M3 + activators housed in place of the La / Y ions, M3 + being Tb3 + and possibly Gd3 +, Ce3 + and / or Bi3 + and M2 + being Mn2 + or Eu2 + 2. Borate-based luminescent matrix according to claim 1, characterized in that it corresponds to the general formula Laluvxy_zGduCevBixTbyEuz (Mg, Zn) B5010, in which: O <u <0.99 O <v K 1 - u - x - y - z O <v1 -uxyz 0 <x <0.3 0.005 <y <0.7 0.005 <z <0.7 u + x + y + z <1 3. Borate-based phosphor matrix according to claim 1, characterized in that it corresponds to the general formula LaluvxzGduCevBixTbyEUz (Mg, Zn) l-rEUrB5010 in which: 0 <u <0.955 0 <v <l - u - x - z O <x <0.3 0.005 4 z <0.7 x + u + z <1 0.005 <r <0.7 4. Borate-based luminescent matrix according to claim 1, characterized in that it corresponds to the general formula Lalu vxy. zGduCevBixTbyEuz (Mg, Zn) in which: 0 u <0.99 O <v1 <1 - uxyz 0O <x <0.3 0.005 <z 0.7 u + x + y + z <1 0.005 < r <0.7 5. A borate-based luminescent matrix according to claim 1, characterized in that it corresponds to the general formula Lal_uvxzGduCevBixEuz (Mg, Zn) 1pMnpB5010 in which: 0 <u <0.99 0 <v 0.3 O < x <l - u - v - z 0.005 <z <0.7 u + x + z <1 0.01 <p 0.3 Borate-based luminescent matrix according to claim 1, characterized in that it corresponds to the general formula   Lal -u-v-x-y-z GduCevBixTbyEuz (M9g Zn) l-.p-rMnp Er B50O -   wherein: 0 <u <0.99 Y <v <1 - u - x - y - z 0 <x <0.3 0.005 y 0.7 0.005 z <0.7 u + x + y + z <0 , 01 <p <0.3 0.005 <r <0.5   Luminescent matrix based on borate according to one of the claims   1 to 6, characterized in that La has been replaced partly or wholly by Y.