HU182915B - Luminescent screen and method for producing the luminescent ternary aluminate usable for the screen - Google Patents

Abstract

Luminescent materials comprising luminescent ternary aluminates having a hexagonal crystal structure corresponding to the magnetoplumbite structure, which contain gadolinium and which are activated by at least one of the elements Pb, Sb, Ce, Sn, Tb, Mn, Cr, and Dy. The composition of the aluminate can be represented in a ternary phase diagram of a system ABC, wherein A represents 1 DIVIDED 2Gd2O3 and at least one of the oxides 1 DIVIDED 2La2O3, 1 DIVIDED 2 Ce2O3, 1 DIVIDED 2Tb2O3, 1 DIVIDED 2Dy2O3, 1 DIVIDED 2Sb2O3, PbO, SnO, wherein at least 1 mol.% A is 1 DIVIDED 2Gd2O3, not more than 60 mol.% A is 1 DIVIDED 2Tb2O3, not more than 20 mol.% A is 1 DIVIDED 2Dy2O3, not more than 20 mol.% A is 1 DIVIDED 2Sb2O3, not more than 35 mol.% A is PbO and not more than 25 mol.% A is SnO, wherein B represents Al2O3, wherein not more than 20 mol.% of the Al2O3 in B may be replaced by Sc2O3, not more than 10 mol.% of the Al2O3 in B may be replaced by Cr2O3 and not more than 10 mol.% of the Al2O3 in B may be replaced by a chemically equivalent quantity of a combination of equimolar quantities of SiO2 and (MgO and/or ZnO), wherein C represents at least one of the oxides MgO, ZnO, 1 DIVIDED 2LiAlO2 and MnO, wherein not more than 20 mol.% of C consists of MnO, wherein up to 98 mol.% of A may be replaced by SrO and/or CaO when simultaneously or equimolar quantity of C is replaced by 1 DIVIDED 2Al2O3, where [A] is at least 0.02, [B] is at least 0.55 and is not more than 0.95, and [C] is at least 1 DIVIDED 2[A], wherein [A] + [B] + [C] = 1. <IMAGE>

Description

BACKGROUND OF THE INVENTION The present invention relates to a screen consisting of a luminescent ternary aluminate crystal having a magnetoplumbite structure having a hexagonal crystal structure. It is a further object of the present invention to provide a process for preparing such an aluminate.

Luminescent ternary aluminates are known from Dutch Patent Specification 7,214,862. These aluminates consist of three oxides: they contain, at Al ₂ O ₃ , at least one large positive ion oxide and at least one small divalent ion oxide such as MgO or ZnO. Their crystal structure is identical or related to the structure of hexagonal magnetoplumbite (PbO · 6Fe ₂ O ₃ ). When the oxide containing the large positive ion is lanthanum and / or cerium oxide, ternary aluminates having the so-called "irregular" magnetoplumbite structure are obtained. The latter structured aluminates are, for example, host lattices for activation with terbium or dysprosium. Highly effective luminescent materials can be produced in this way.

Until now, it has been hypothesized that the formation of irregular magnetoplumbitic temerate aluminate crystal lattices requires the use of relatively high ionic oxides of rare earth metals such as lanthanum oxide or cerium oxide. The radii of the trivalent lanthanum and cerium ions are 1,016 and 1,034 Å respectively (see Handbook of Chemistry and Physics, Cleveland, Ohio).

SUMMARY OF THE INVENTION It is an object of the present invention to provide a novel luminescent umbrella consisting of a magnetoplumbit crystal structure luminescent ternary aluminate and a process for the production of an aluminate for use with the umbrella.

The umbrella of the present invention having a magnetoplumbitic structure-like hexagonal luminescent aluminate screen is characterized in that the aluminates contain gadolinium; can be activated with lead, antimony, cerium, tin, terbium, manganese, chromium or dysprosium, or more of these elements; is characterized by a phase diagram ABC in which A is 1 / 2Gd ₂ O ₃ and al / 2La ₂ O ₃ , 1 / 2Ce ₂ O ₃ , 1 / 2Tb ₂ O ₃ , 1 / 2Dy ₂ O ₃ , 1 / 2Sb ₂ O at least one, whereby at least 1 mole% l / 2GD ₂ 0 ₃ by weight, a maximum of 60 mole% l / 2TB ₂ 0 ₃ by weight, up to 20 mol% t / 2Dy ₂ 0 ₃ cent of _3, PbO, oxides of SnO containing up to 20 mole% l / 2Sb ₂ O ₃ , up to 35 mole% PbO and up to 25 mole% SnO; B is A1 ₂ O _3, whereby the A1 ₂ O _3, a maximum of 20 mol% Sc ₂ O ₃ be substituted cent and up to 10 mole% of Cr ₂ O ₃ cent; C is at least one of MgO, ZnO, l / 2LiA10 ₂ and MnO, with C up to 20 mol% of MnO; up to 10 mol% of A1 ₂ O _{3 may} be replaced by an equivalent amount of SiO ₂ and MgO and / or ZnO; however a maximum of 98 mol% of SrO, Al and / or substitution of CaO-Al and C, however, equivalent quantities l / 2AL cent ₂ O _3, all of the A + SrO + CaO amount of at least 1% per / 2GD ₂ O ₃ consists of; and the aluminate has an A content of at least 0.05, a B content of at least 0.70 and a maximum of 0.95 and a C content of at least 2/3 of the A content.

Surprisingly, our attempts to develop the invention have shown that ternary aluminates of irregular magnetoplumbitic structure can also be prepared in the form of aluminates containing 1 / 2Gd ₂ O ₃ as oxides with large positive ions. This was unexpected because the radius of the trivalent Gd ions (0.938 Å) is significantly smaller than that of the La and Ce ions.

The luminescent aluminates of the present invention are ternary compounds, the composition of which in the ABC temperature diagram is represented by A being an oxide having a large positive ion and C being an oxide having a small divalent ion and B being alumina.

It has been found that the new Gd-containing aluminates can form a complete series of mixed crystals having the same structure as the known Laes and / or Ce-containing aluminates. Therefore, not only l / 2Gd ₂ O ₃ but also l / 2La ₂ O ₃ and l / 2Ce ₂ O ₃ can be used as oxides in the luminescent aluminates of the invention, but it is necessary that the oxide A is at least 1 mol% l / 2Gd _{2 in} each case. Contain O ₃ .

Effectively luminescent materials are available when the oxide A contains 1 / 2Ce ₂ O ₃ . In addition, activation with one or more of the elements Tb, Dy, Sb, Pb and Sn appears to result in luminescent materials. The oxides of these activator elements are also part of the oxide A. Effective luminescence can occur even when 0.1 mol% of oxide A is an oxide of one of the aforementioned activator elements. There are certain limits to the maximum amount of oxide activator used, because of the limited solubility in the crystal lattice called these oxides and / or because of the high content of activator material, which results in luminescence due to concetration quenching for practical purposes. too small. Therefore, the alumina of the invention has an oxide A of not more than 60 mol% l / 2Tb ₂ O ₃ , not more than 20 mol% l / 2Dy ₂ O _s , not more than 20 mol% l / 2Sb ₂ O ₃ , not more than 35 mol% Contains PbO and up to 25 mole% SnO. Oxides A of the aluminates of the present invention contain at least 1 mol% l / 2Gd ₂ O ₃ , even if they contain more than one of the aforementioned oxide activators.

The Al ₂ O _{3 of} the aluminates of the invention (designated as B in the above formula) was replaced by up to 20 mole% Sc ₂ O ₃ . This substitution generally has little effect on the luminescent properties and provides no additional benefits. Using more than 20 mole% Sc ₂ O _{3 results} in materials that are too low in luminescence (luminescent flux) and, in addition, too expensive due to the use of the expensive scandium element. It seems that the aluminates can be activated with chromium. Chromium oxide can replace part of A1 ₂ O ₃ . Effective chromium emission can occur even when 0.1 mol% of B is Cr ₂ O ₃ . No more than 10 mole% of B can be replaced by Cr ₂ O ₃ , since the luminous flux (luminescence flux) obtained at a higher Cr content is too low due to concentration suppression.

It should be noted that oxide B may also be composed of gallium oxide, since they are also temeric compounds whose structure is related to magnetoplumbit. The use of Ga ₂ O ₃ in B oxide has no advantages. In addition, gallium is a more expensive element than aluminum, so gallium-free aluminates are preferred. The oxide containing small divalent ions is C, MgO, ZnO, or a mixture thereof. In addition, this role can be performed by l / 2LiA10 ₂ . It seems that the aluminates can be activated with manganese. MnO is then part of the C oxide. An effective Μη emission can be achieved even if 0.1 mol% of C consists of MnO. The MnO content of C over 20 mole% is not expected to increase to 2182,915 because at such high Mn content, too low luminescence flux can be achieved due to concentration suppression.

It is reported that according to the present invention The phrase aluminate Al ₂ O ₃ up to 10 mol% of an equivalent amount cent _SiO2 and MgO and / or ZnO al replaced: Pal ₃ O ₂ -> ₂ + pMgO Psion (ZnO ). With such a substitution, the crystalline structure of the aluminate is retained and the luminescent properties are little changed.

The experiments further revealed that the novel Gd-containing ternary aluminates of irregular magnetoplumbitic structure and the known ternary aluminates of magnetoplumbitic structure containing Sr and / or Ca were highly soluble. Therefore, in the aluminates of the invention, A 98 may be substituted with 98% by weight of SrO and / or CaO, provided that at the same time the equimolar amount of C oxide is replaced by 1 / 2Al ₂ O ₃ qA + qC - * qSrO (CaO) + q · 1 / 2A1 ₂ O ₃ (for example: ql / 2Gd ₂ O ₃ + qMgO - * - * qSrO (CaO) + q · 1 / 2A1 ₂ O ₃ ). The compounds thus prepared have magnetoplumbitic or irregular magnetoplumbitic structure and, upon activation, produce luminescent materials. Even with this substitution, the oxide A and the total amount of SrO and CaO are at least 1 mol% / 2Gd ₂ O ₃ .

The composition of the aluminates of the present invention is within the area delimited by [A]> 0.02, 0.55 <[B] <0.95 and [C]> 1/2 [A] in the ABC Thimer diagram. In these mathematical inequalities, [A], [B] and [C] represent the oxide content or molar fraction of A, B and C, and [A] + [B] + [C] - 1. Figure 1 shows the ABC ternary phase diagram. Each ternary compound is represented by a single point within the triangle ABC. The composition of each of the aluminates of the invention is characterized by a single point within the PQRS rectangle.

The luminescent aluminates of the present invention having a content of at least 0.05, a content of B of at least 0.70 and a content of C of at least 2/3 A exhibit very good luminescent properties and whose composition within the phase diagram of FIG. is characterized by a point on the TUV triangle.

The highest luminescent flux is given by aluminates having an A content equal to their C content and a B content of at least 0.70 and at most 0.85. In the phase diagram depicted in Figure 1, these compounds are located on or near the XY line.

In the aluminates of the present invention, MgO and / or ZnO is used as the C oxide, since these give the best results.

Among the aluminates of the invention, the most preferred are the lead-activated compounds in which the oxide A consists of 25-90 mol% / 2Gd ₂ O ₃ . The lead content is chosen such that 1-35 mol% of A is PbO. These materials are very effective at exhibiting the typical linear emission of gadolinium at ca. At 313 nm, lead acts as a sensitizer for gadolinium emission. These aluminates are very suitable for the production of photochemical reaction burners and especially for medical irradiation burners, such as low pressure mercury vapor burners. The aluminates of the present invention, which are the most effective Gd emission materials known to date, have the great advantage that when used in burners, their radiation flux changes only slightly over the lifetime of the burner.

It should be noted that Gd emission is also achieved with Sb-activated Gd-containing aluminates. However, these Sb-sensitized compounds appear to be generally less effective than the Pb-sensitized ones.

Another class of luminescent aluminates of the present invention are those in which at least 25 mol% of the oxide A is present in l / 2Gd ₂ O ₃ and which are activated not only by lead but also by one of the elements Tb, Dy, Mn or Cr. . These aluminates are very effective in providing Tb, Dy, Mn, and Tb. Cr typical emission. In these materials, the excitation energy is absorbed by lead and then transmitted through one or more Gd ions to the Tb, Dy, Mn or Cr activators mentioned above. In particular, Tb-activated aluminates have great advantages. When excited by short-wave ultraviolet radiation, such as 254 nm of a low-pressure mercury vapor lamp, these aluminates exhibit essentially the quantum efficiency of the most effective Tb-emitting materials known to date. Their advantage is that essentially no lead and gadolinium emissions are observed and that the use of these aluminates in burners results in only a very small reduction in luminescent flux.

A third preferred group of aluminates of the invention are cerium-activated compounds. There is virtually no concentration suppression for this activation, so that the oxide A may consist of _{1 to} 99 mol% of 2Ce ₂ O ₃ . The Ce-emission can be very effective, and the ultraviolet spectrum is large wavelength lane (the emission band maximum (? _Max) of the aluminate depending on the composition of 305 to 360 nm and the emission band half-width (λ _1/2) is about 65 gm). These materials are preferably used in burners to stimulate photochemical processes.

A further preferred group of aluminates according to the invention comprises at least one of the activator elements Tb, Dy, Mn or Cr in addition to Ce. In these compounds, the excitation energy is transmitted by Ce, as a sensitizer, to the second activator, and a characteristic emission of the second activator element occurs.

Activation with bivalent tin yields aluminates which exhibit tin emission by, for example, 254 nm wavelength radiation. This emission occurs in the near range of the ultraviolet spectrum (λ max ⁼ 355-375 nm, ~ 60 nm).

It should be noted that it is possible to transfer excitation energy from tin to the above-mentioned elements Tb, Dy, Mn and Cr, but tin-sensitized aluminates are generally less effective than the Ce-sensitized compounds described above.

The luminescent aluminates of the present invention may be prepared by a solid phase reaction at a high temperature treatment of the starting material mixture. Preferably, the luminescent aluminates are prepared by blending Α, B and C oxides and / or compounds providing these oxides upon heating, with 0.1 to 10 mol% of the metal of the oxide B and / or A and / or 1 to 100 mol% of the metal of C-oxide is added in the form of fluoride and then heated to 1200-1500 ° C.

It has been found that using one of the constituents in the form of fluoride greatly contributes to the speed and completion of the formation reaction.

The method of carrying out the procedure for which 3

-3182 915 is characterized in that the aluminum content of the mixture is introduced in the form of aluminum fluoride.

A further preferred embodiment of the process according to the invention is the addition of 0.05 to 0.5 moles of BaO and 0.3 to 3 moles of Al ₂ O ₃ per mole of aluminate to be produced, or the compound forming these oxides upon heating. mix. The experiments show that the aluminates so prepared have a higher luminescent flux than the aluminates to which BaO and Al ₂ O ₃ were not added. When excess BaO and Al ₂ O _{3 are} added, the reaction product usually contains barium aluminum in addition to the desired luminescent aluminate. This barium aluminate does not need to be removed as its amount is very small and not distracting.

The advantages of the luminescent screen of the present invention are summarized below. The aluminum used to make the umbrella is highly efficient at absorbing excitation radiation, has a favorable absorption maximum wavelength, has a clean emission spectrum, and can be produced by a simple and economical process. Some of the aluminates of the invention containing activator and sensitizer ions do not show any sensitizer emissions, they produce very pure activator emissions.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is illustrated by the following drawing, embodiments and measurement results.

Figure 1 is a diagram of the ABC ternary phase diagram described above.

Figure 2 shows the spectral energy distribution of the emission of lead-activated aluminate.

Figure 3 shows the emission spectra of a lead and dysprosium activated aluminate.

Figure 4 is an emission spectrum of a lead and manganese activated aluminate.

Figure 5 illustrates the emission spectra of lead and chromium activated aluminate.

Fig. 6 is a schematic and cross-sectional view of a cerium-activated aluminate emission spectrum, Fig. 7 is a ceramic-terbium-activated aluminate emission spectrum, and Fig. 8 is a schematic view of a low pressure mercury vapor lamp of the invention.

Example 1

2.45 g of Gd ₂ O ₃ ,

0.61 g MgO,

8.26 g of Al ₂ O ₃ ,

0.41 g of A1F ₃ · 3H ₂ O and

A mixture of 0.50 g of PbO is prepared. The mixture is heated in an oven at 1450 ° C in air. After cooling and pulverization, the resulting product is a luminescent aluminate of the formula Gd _{0 90} Pb ₀ isMgAl _u O ₉ . X-ray diffraction analysis shows that the aluminate has an irregular magnetoplumbite crystal structure. After irradiation with a low-pressure mercury vapor lamp (predominantly 254 nm), the alumina exhibits a characteristic linear emission of Gd. Figure 2 shows the emission spectrum of a very narrow band with a maximum of 313 nm (λ _1/2 half-width: about 4 nm). This figure shows the wavelength λ on the horizontal axis and the relative intensity E on the vertical axis in arbitrary units. The absorbance (A) of the ultraviolet excitation radiation of the aluminate is 93%. The maximum value of the emission band 4 is Gdo, 5La _{0 |} 69% of the known bismuth activated borate of formula 487Bi _0j0 , ₃ B ₃ 0 ₆ , which also exhibits Gd emission.

2-17. example

In a manner analogous to that described in Example 1, a series of lead-activated aluminates (Examples 2-15) are prepared in which the aluminate composition is variable. Two additional antimony-activated aluminates were prepared by using Sb ₂ O ₃ instead of PbO in the mixture to be heated. These aluminates also exhibit effective Gd emission. The results of measurements with these substances are shown in Table 1. The table shows, in addition to the formula of the aluminate produced in each embodiment, the maximum value of the emission band as a percentage of the maximum value of the above known borate and the percentage of absorbance of excitation radiation.

Table 1

Example Formula Maxi- decimal value THE First Gd _0i9 oPbo, i5MgAlnO _{) 9} 69 93 Second Gd _2i 8oPbo, ₃ oMg ₆ Al ₂₂ 0 4 _3i 5 ₀ 41 81 Third Gdo, 87 Pb 0 .ioMgg Al ₂₆ O _4ft , 505 57 74 4th Gdo, ₉₂ Pbo _i i ₂ MgAl6On ₎ 5 57 89 5th Gd _O! 8 ₇ Pbo _j20 Mg4Al ₃₀ O50,505 51 70 6th Gd _o> 87Pbo, 2oMgAl íeChó.sos 66 86 7th Gdo, 8 ₇ Pb 0.2oMg Al ββΟδό, 505 45 68 8th Gdo, 9oPbo, isMgAl io, 8Sco ₂ Öi ₉ 64 94 9th _{Gdo j9} oPbo, isMgAl ioScOj ₉ 49 87 10th Gd ₀ , ₉ oPb _0; i5MgAl ₉ Sc20 ₁₉ 34 75 11th Gdo ^ oPbojsMgo.svZnooaAl j] Oi ₉ 71 93 12th Gdo ^ oPbojsMgo ^ oZno ^ oAl) iO _i9 68 93 13th Gdo, ₉ oPbo, isMgo, 5oZn _{o 5O} A1 jiOj ₉ 64 93 14th Gdo _i9 oPb _0il5 Mg _0j2 oZn ₀₎ a 'Al ijOjo 60 93 15th Gd _{O 9} oPb _o , is Zn Al 110 j ₉ 58 93 16th GDO ^ ^ SboyMgAlnO 33 65 17th GDO íSbo ^ ^ MgAlnOig 33 67

Example 18

In a manner analogous to that described in Example 1, lead-activated aluminate is prepared, except that 0.25 moles of BaCO ₃ and 1.50 moles of Al ₂ O ₃ are added to each mole of the aluminate. For this purpose

1.27 g of Gd ₂ O ₃ ,

0.40 g BaCOr,

0.32 g MgO,

5.66 g of Al ₂ O ₃ ,

0.14 g of A1F ₃ · 3II ₂ O,

A mixture of 0.34 g PbO was prepared. The product is an aluminate of the formula Gdo ^ sPbo.msMgAlu O ₁₉ , which exhibits an irregular magnetoplumbite crystal structure. The aluminate contains a small amount of barium aluminate, which however does not interfere at all.

Example 19

The procedure described in Example 18 was followed, but the mixture for the heat treatment contained ZnO instead of MgO.

-4182915

20-22. example

Three lead-activated aluminates were prepared as described in the previous examples in which aluminum was replaced with an equivalent amount of Si and Mg.

The following Table 2 provides the formulas for the aluminates, the maximum values, and Table 18-22. shows the absorption of the materials of Examples 1 to 4.

Table 2

Example Formula ph THE 18 ^1} Gd ₀ 875 Pb 0.1875 MgAl 11 018 70 81 19 ° Gdo 875 Pbo, 1875 Zn Al]! 0 ₁₉ 74 81 20 ^{1 2)} Gdo9oPbo, ioMgi5 AlioSio, s Oi8.95 60 85 21 ³⁾ Gdo, 875 Pbo, 125 Mgl, 25 Al] O, 5O SÍo, 25 018.94 64 77 22 ⁴⁾ Gd ₀ 875Pbo, 12sMgl, 25 Alio, 5ClS10, 2sO18.94 73 75

1) To each mole of aluminate were added 0.25 moles of BaCO ₃ and 1.5 moles of Al ₂ O ₃ to the mixture to be heated.

2) The mixture is heated to 1500 ° C.

3) 0.25 mol BaCO ₃ and 1.375 mol Al ₂ O ₃ were added. Heating was carried out at 1400 ° C.

4) 0.25 M BaCO ₃ and 1.44 M Al ₂ O ₃ were added to the mixture. Heating was carried out at 1500 ° C. The material has a quantum efficiency of 22-55%.

23-27. EXAMPLE 5 Five lead and terbium activated aluminates were prepared by heating the starting mixture at 1400 ° C (Examples 23-25) or 1500 ° C (Examples 26 and 27) under nitrogen. Table 3 shows the formulas for the substances. The table shows the quantum efficiency of these aluminates as a percentage of the 254 nm wavelength radiation and the% A absorbance of the radiation. In these materials, the scintillating radiation is absorbed by lead and transmitted by one or more Gd-ίοη to my terbium activates. The materials exhibit effective terbium emission, with virtually no lead and gadolinium emissions observed.

Table 3

Example Formula q A

23. Gdog Tboi Pboi Mgo9 Aljjj O9 51 85

24. Gdo _; 8s Tbo.iPbo.osMgo ^ s Aljios O19 56 72

Gd _Oi 67Tbo, 22Pb _o , nMgi _{> 12} Α1ιο, 95θιβ, 9981 73

26 ²⁾ Gdo ^ eTbo ^ iPbo ^ íMgioéAlnOi895s 75 82

Gdo ^ Tbo ^ Pbo ^ õMgj oeAljiO1393 76 85

1) 0.10 mol BaCO ₃ and 0.60 mol Al ₂ O ₃ are added to the mixture to be heated.

2) 0.05 moles of BaCO ₃ and 0.30 moles of Al ₂ O ₃ are added to the mixture to be heated.

28-31. example

Effective transfer of scintillation radiation by Gd ions to Dy, Mn or Cr is also possible in lead-activated aluminates. Table 4 shows the formulas for four such aluminates. The table also shows the values of the quantum efficiency q and the absorbance A.

Table 4

Example Formula q THE 28th Gdo, 8o Dyo.ioPbo.isZnAln O19 37 89 29Ό 3O ²⁾ Gdo, eo Dyo.ioPbo.is MgAln O19 Gd ₀ , 875 Pbo, i25 Mgi.125 Mn _{0 125} Al 10.50 28 87 31 ³⁾ Siof, 2501894 31 82 Gd _O , 9oPbo, 15 MgAl 11.49 C ^r 0.01 θ 19.75 30 91

1) Figure 3 shows the spectral energy distribution of the radiation emitted by a material excited by 254 nm wavelength radiation. The emission spectrum is approx. It consists of characteristic Dysbands of 480 and 575 nm wavelengths. In addition, the linear emission of Gd can be found at 313 nm (Figure 3 shows this in a 10-fold reduced scale).

2) 0.25 moles of BaCO ₃ and 1.44 moles of Al ₂ 0 ₃ are added to the mixture to be heated. Figure 4 shows the emission spectra of this aluminate, which consists of the green manganese band and has a maximum of about. 525 nm. The Gdemission can also be observed here.

3) Figure 5 shows the emission spectrum of this material. It consists of a narrow band with a maximum of approx. 700 nm.

Example 32

1.61 g of Gd ₂ O ₃ ,

0.51 g MgO,

7.05 g of Al ₂ O ₃ ,

A mixture of 0.17 g of A1F ₃ -3H ₂ O and 0.65 g of CeO _{2 is} prepared. This mixture is heated for 2 hours at 1450 ° C in a furnace through which nitrogen is bubbled (5 L / min). After cooling and pulverization, a luminescent aluminate, defined as Gd _O 7 _° Ce _{o> 3} o MgAlnO 2, is obtained. It exhibits Ce emission at 254 nm wavelength radiation (peak at about 340 nm near the ultraviolet spectrum). The emission spectrum is shown in Figure 6. The relative intensity of emitted radiation I is 93% relative to that of a standard luminescent material. This standard is known for lead-activated barium disilicate which emits in the same part of the spectrum. The scintillating radiation has an absorption of 93%.

33-47. example

In a manner analogous to that described in Example 32, a series of target-activated aluminates of various compositions are prepared. Table 5 shows the formulas of these materials (Ex. 33-45) and the results of the measurement of the relative intensity I, as a percentage of the standard mentioned in Example 32, and

-5182915 excitation radiation A absorption values. Examples 46 and 47 relate to tin-activated aluminates. These materials have an approx. They are emitted at a maximum band of 375 nm (λ i / 2 = 60 nm).

· 5. spreadsheet

Example Formula I THE 32nd Gdo ₎ 7oC ^e O, 3oMgAln O19 93 93 33rd Gd ₀ 99 Ce _0j oi MgAl η θ 19 44 57 34th Gd _o , 9oCe _o joMgAln O19 86 89 35th Gd _0; 5oC ^e o, soMgAliiOi9 86 95 36th Gdo ^ s Ce _Oj 75 MgAl 11019 73 96 37th Gdo.oi Ceo, 9 ₉ MgAlii O19 85 97 38th La ₀ , ₂ Gd _0> s Ce ₀ , ₃ MgAl 11019 85 94 39th La ₀ , 5 Gd _0j2 Ce ₀ , ₃ MgAlji Oj9 85 93 40th La _{0> 2} Gd _{0> 5} Ce _0i3 ZnAlii O19 80 94 41st La _{0> 5} Ge _{0; 2} Ce _{0 3} ZnAln O19 85 93 42nd Gd ₀ , 9 Ce _0> i ZnAl n019 78 91 43rd Gd ₀ , 7 Ce _{0> 3} ZnAl 11019 65 96 44th Gd _o> io Sr ₀ 8s CeoosMgoqs Aln.ss θΐ9 1.) - 45th Gdoso Sr _0> 4s Ce _0j os Mgo ^ s A11145 019 2.) - 46th GdSn ₀₎ i MgAln Oigj 38 60 47th GdSn ₀ , i ZnAl _u Oi9 _{ i 41 55

1) Quantum efficiency at 254 nm excitation: 77%; Λ _max = 310 nm.

2) Quantum efficiency at 254 nm excitation: 55%; A _max = 340 nm.

48-54. example

In a manner analogous to that described in Example 32, Ce-activated aluminates containing Tb, Dy or Cr as the activator were prepared. These materials show the radiation characteristics of this latest activator. Table 6 gives the formulas for these materials, the quantum efficiency of q, and the absorbance of A.

Table 6

Example Formula q THE 48th Gd _0> 5 ₂ Ce ₀ , 5 Tbo, ₃₃ MgAln O19 73 91 49 ° Gdo { ₃ 7Ce _o3o Tb _Oj33 MgAln θΐ9 74 95 50th Gd ₀₂₂ Ce ₀ , ₄ 5 Tb _{0; 33} MgAln O19 76 96 51st Gd _{0 0} i Ce _Oj66 Tb _{O 33} MgAln O19 77 96 52nd Gdo _{> 3} 7 Ceo _{> 3} o Tb 0.33 ZnAl η 019 63 96 53rd Gd _{O |} 6o Geo, 30 θΥο, ιο ZnAl π θ 19 17 94 54th Gd ₀ , 6s Ce ₀ 3 ₀ MgAl !! Croos Oj ₉ 20 -

1) Figure 7 shows the emission spectrum of this material. In addition to the typical Tb emission, a small amount of Ce band emission can be observed.

Figure 8 is a schematic and cross-sectional view of a low pressure mercury vapor lamp according to the invention. The lamp has a tubular glass wall. At the ends of the lamp, electrodes 2 and 3 are arranged, between which discharge occurs during operation. The lamp contains a mixture of noble gas (used as a starter gas) and a small amount of mercury. The wall 1 also serves as a substrate 6 for the luminescent layer 4. This layer contains the luminescent aluminate of the invention. The layer 4 can be applied to the wall in a conventional manner, for example by means of a suspension containing luminescent aluminate.

Claims (9)

PATENT CLAIMS 1. A luminescent screen consisting of a hexagonal crystalline luminescent ternary aluminide on a substrate, associated with a magnetoplumbite structure, characterized in that the aluminate contains gadolinium, one or more of Pb, Sb, Ce, Sn, Tb, Mn, Cr or Dy activated. can be determined by an ABC terner phase diagram in which A is L / 2GD ₂ O _3, the l / 2LA ₂ O _3, l / 2 Ce ₂ O _3, I / 2TB ₂ O _3, I / 2Dy ₂ O _3, I / 2SB ₂ O _3, PbO or SnO oxides one or more, with A at least 1 mol% l / 2Gd ₂ 0 ₃ , 60 mol% l / 2Tb ₂ 0 ₃ , not more than 20 mol% l / 2Dy ₂ 0 ₃ , not more than 20 mol% l / 2Sb Containing ₂ O ₃ , not more than 35 mol% of PbO and not more than 25 mol% of SnO, B is A1 ₂ O ₃ , of which up to 20 mol% can be replaced by Sc ₂ O ₃ and up to 10 mol% can be substituted by Cr ₂ O ₃ . C is at least one of MgO, ZnO, 1 / 2LiA10 ₂ or MnO, while C contains up to 20 mol% of MnO, with up to 10 mol% of Al ₂ O _{3 being} equivalent to SiO ₂ and MgO and / or ZnO and wherein up to 98 mol% of A is substituted with SrO and / or CaO and at the same time C is equimolar to 1 / 2Al ₂ O ₃ , whereby at least the total amount of A + SrO + CaO It consists of 1 mol% / 2Gd ₂ O ₃ and the aluminate content is not less than 0,05, not less than 0,70 and not more than 0,95 and not less than 0,95 is for C; 2/3 of its content. An embodiment of a luminescent screen according to claim 1, characterized in that the aluminate has an essentially C content and a B content of at least 0.70 and at most 0.85. An embodiment of a luminescent screen according to claim 1 or 2, characterized in that the aluminate activated by lead is 1 to 35 mol% of PbO and 25 to 99 mol% of 2Gd ₂ O ₃ . An embodiment of a luminescent screen according to claim 3, characterized in that the aluminate is activated in addition to lead by one or more elements Tb, Dy, Mn or Cr. 5. An embodiment of a luminescent screen according to claim 1, wherein the aluminate is activated by cerium, wherein A is 1 to 99 mol% / 2Ce ₂ O ₃ . An embodiment of a luminescent screen according to claim 5, characterized in that the aluminate is activated by one or more of the elements Tb, Dy, Mn or Cr, in addition to cerium. 7. Procedure 1-6. The luminescent screen for use in a luminescent screen according to any one of claims 1 to 4, characterized in that the oxides A, B and C of the aluminate components or the compounds forming these oxides for heating are mixed with 0.1 to 10 mol% of the metal of the oxide B, 1 to 100 mol% of the metal of the oxide or C oxide is added in the form of fluoride and the mixture is then heated at 1200 to 1500 ° C. 8. A process according to claim 7 wherein 0.1 to 10 mol% of aluminum is added in the form of aluminum fluoride. 9. A process according to claim 7 or 8, characterized in that 0.05 to 0.5 moles of BaO and 0.3 to 3 moles of Al 2 O 3 are added to each mole of aluminate, or compounds forming these oxides are added for heating. even to the mixture.