DE2118531A1 - Fluorescent - Google Patents

Description

P- fr-tanwe

i.?■ PENFABRIEKEH

April 15, 1971

If.V. Philips' Gloeilampenfabrieken, Eindhoven / Holland

Fluorescent

The invention relates to a phosphor which is a luminescent silicate of an alkaline earth metal and of Contains lanthanum and / or yttrium, which silicate has the apatite crystal structure. Furthermore relates the invention relates to the use of such a phosphor in a luminescent screen of a low-pressure mercury vapor discharge lamp.

From the article by H. Schwarz in "Inorg.Sucl.Chem.Letters", Br. 1, 231-236 (1967) a number of silicates are known, which by the general formula

can be represented. The in the mentioned article, The compounds described are strontium lanthanum compounds (in the general formula Me then represents strontium and

Me lanthanum) and show all the.

4817 109851/1811

Jü

-2- PHN. 4817 C.

Apatite crystal structure if the following conditions are met: a + 1,5b-12 + x, 06x ^ 2, 0 ^ a ^ .4t and further where if £ 0. a ^ .2, the condition is met that a + b is £ 8.66, and if 2 is £ - a ^ .4, the condition is met, that a + b ^ 10. It has been shown that strontium is completely or partly by other alkaline earth metals (which in this description also include the elements magnesium, zinc and cadmium) and completely by lanthanum or can be partially replaced by yttrium and the rare earths, the apatite crystal structure being retained.

The above-mentioned formula with the above conditions encompasses a very large class of compounds which can be referred to as silicate apatites. It is known of some of these silicate apatites that they ε form phosphors when activated. Thus, in the article by J. Ito in "The American Mineralogist", No. 2 ±, 890-90? (1968) described the activation of silicate apatites with europium and terbium according to the above-mentioned formula, in which a "2" and b "8. It is mentioned that these silicate apatites exhibit an effective luminescence when excited with ultraviolet radiation with a wavelength of 313 nm.

A phosphor according to the invention contains a luaines

sizing silicate of one or more of the alkaline earth metals and of lanthar and / or yttrium, which silicate has the apatite crystal structure, and is characterized in that the silicate of the formula

corresponds to the formula Me in which at least one of the elements Ca, Sr, Represents Ba and Mg, with up to 50 Mo 1 $ of the mentioned elements being replaced by Zn and / or Cd can be replaced, and in which also Me at least one »of the elements La and Y, and A is an activator from the group Sb, Pb, Sn,

109851/1811

-3- PHN. 48-iY C

Represents Sb and Mn, Fb and Mn, where A replaces an equivalent amount of the elements Me and / or Me, while also satisfying the conditions will:

a + 1.5b - 12 + χ

04.x ^ 2

0 «£ y ^ r *, 5

£ 0 .p - £ 4.5

y + P £ 4i5

0.05 £ q ^ r 0.8 and

4/3 £ b / a - £ 8, where, if y - 0, then 2 £ b / a ^ 8, if a - ^. 2, then * a + b ^ 8, 66, if a is £ 2, then a + b <£ 10, and if both a + b · £ · 9 and χ «0, then y is £ .1.5.

Investigations which have led to the invention have shown that all of the silicate apatites mentioned in the article by Schwarz can be activated with the elements mentioned above. It has been found that those of the large number of apatite lattices described by Schwarz, for which the ratio between Me ¹¹¹ and Me ^ atoms is between 4/3 and 8, form particularly effective phosphors when activated with the elements mentioned. With the phosphors according to the invention, when excited with radiation of a low-pressure mercury vapor discharge, light yields can be obtained which are two to three times higher than that of the known silicate apatite activated with europium or terbium. This was by no means to be expected, not even on the basis of the aforementioned article by Ito. It is known that trivalent europium and trivalent terbium can be excited in almost all basic lattices with ultraviolet radiation with a wavelength of 313 bsi, provided that the activator is at a satisfactory level

109851/1811

-4- PEN. 4Θ1? C.

Way is included in the basic grid. Near that wavelength namely, the trivalent europium as well as the trivalent Terbium has a characteristic absorption line in the absorption spectrum · So it cannot be deduced from Ito's article whether the The phosphors described therein have a satisfactory light yield when excited with ultraviolet radiation with a wavelength different from 313 n » exhibit. For many applications it is desirable that the maximum of the excitation spectrum of a phosphor is in the vicinity of 254 ma is because then, as is known, a low-pressure mercury vapor discharge can be used particularly advantageously as the excitation source. in the Article by Ito is, in particular, about the possibility of suggestion with Radiation with a wavelength of 254 nm, no information provided. Fernei can on the basis of the article by Ito the size of the light output Activation of these silicate apatites with elements other than europium and Terbium cannot be predicted by any means. Studies have shown that the luminescent silicate apatites according to the invention in general a high absorption for radiation with a wavelength of 254 nm exhibit. It also turns out that in many cases that too Maximum of the excitation spectrum near this wavelength of 254 nm lies. As a result of these two properties, the light yield of the luainescent silicate apatites according to the invention can be particularly high and these silicate apatites can be particularly beneficial in conjunction with a low pressure mercury vapor discharge.

It should be noted that from the Dutch Patsntan-

Luminescent halosilicate apatites are known whose basic lattice corresponds to the Forael: Me ^ Me ^ ¹¹ (SiO. ) G> ₂ . Here, L represents one halogen, in particular fluorine. It has been found that

109851/1811

-5- PHN. 4817 C.

these halosilicate apatites generally have a lower luminous efficacy than the silicate apatites according to the invention. Furthermore, the known halosilicate apatites have the major disadvantage that they are a Halogen contained in the basic lattice * The consequence of this is that they . Can be very difficult to manufacture because of large quantities of the activator and silicon disappear in the form of halides during manufacture can. On top of that, the use of fluorine has the disadvantage that the quartz shells used in its manufacture be severely attacked.

The position of the maximum of the emission spectrum of the silicate apatites according to the invention depends on the activator used and on Basic grid dependent. Manganese can be used as an activator in conjunction with antimony or lead. Next to the antimony or lead band appears then a manganese band in the emission spectrum at around 390 nm.

As alkaline earth metal in the silicate apatites according to the Invention calcium, strontium, barium and magnesium can be used. These elements can be partially, namely up to 50 Mo 1 $, by zinc and / or cadmium. If only zinc and / or cadmium are used as the alkaline earth metal, phosphors are obtained which in practice are less useful because their light output is lower.

If the silicate apatites according to the invention do not contain phosphorus included (y - 0 in the formula) is the ratio b / a between the Vercs; 2 and θ should be selected because otherwise phosphors are obtained which have too low a luminous efficacy.

It has been found that in the silicate apatites according to the invention in general up to 75 % (y ir: 4.5) of the silicon can be replaced by phosphorus. The apatite structure remains

109851/1811

-6- PHN. 4817 G.

and phosphors are obtained with a luminous efficacy that is comparable to the luminous efficacy of the silicate apatites that do not contain phosphor, or even with higher luminous efficacies. When a. According to the invention, silicate apatite contains phosphorus, the ratio b / a can be selected in a wider range, namely between 4/5 and 8. As is evident from the above conditions, in silicate apatites, for which both a + b ^ = 9 and χ - 0 hold, only up to 25 ° / ° (y ^ r 1.5) of the silicon can be caused by phosphorus be replaced. In this case the apatite structure disappears with higher amounts of phosphate, whereby the good luminous properties are also lost.

As is evident from the above formula and the above conditions, the silicon in the silicate apatites according to the invention can be replaced by germanium up to 75 °. This is because it has been found that such a replacement does not affect the luminescence properties or does not affect them at all. When replacing more than $ 75 of silicon with germanium values obtained in practice with regard to the luminous efficacy

are less useful * If both germanium and ^ phosphorus are used, not more than 75 Ί ^{0 of} the silicon may be replaced by these elements (y + ρ £

The element designated by Me preferably consists essentially of a luminescent silicate apatite according to the invention from calcium and / or strontium and the activator is antimony or lead or one of these two elements in conjunction with manganese, while The highest 50 $ of silicon has been replaced by germanium. The Phosphate content y selected between 0.1 and 1.5. This is because substances with a high light yield are obtained.

The highest light yields are achieved with silicate apatites

109851/1811

-7- PHH. 4817 O.

TTT T ™ "

of the invention in which the ratio between Me and Me " ¹ atoms is between 3t5 and 4t5, and in particular when this ratio is 4.

The invention will now be on hand einas manufacture * "- embodiment and a number in the form of tables summary M2S3ergebniese nSher explained · Preparation:

A mixture of 0.745 g CaCO ,, 3.360 g Y ₂ ° 3 ' ¹ »442 g SiO ^ and 0.117 g S ^ ₂ O. is prepared. This mixture is heated to a temperature of about 135 ° C. for about two hours. The heating atmosphere is nitrogen old some (e.g. 2) vol. J £ water vapor. After cooling, the heating product obtained is ground and sieved and then heated again for two hours at 135 ° C. in the same heating atmosphere. The product obtained in this way is ground and sieved after cooling. The luminescent silicate apatite produced in this way corresponds to the formula Ca _{1 86} Y „/ ^ C ⁰¹ - ⁰ ^ ⁰ ! 02 ^'Sb 0 2' ^{and has} * ^ei ~ ^An excitation with radiation of a mercury vapor ITiederdruck Entledung a luminous efficacy of 130% to (in relation to a standard product measured). As a standard product, an activated with antimony and manganese calcium halophosphate is used, which is mixed with nichtlumineszierendem Calciunoarbonat in amounts such that the Lichtauebeute has decreased to about 54 ° i of the original value. The absorption of the ultraviolet radiation emitted from the low pressure mercury vapor discharge is 79 #.

The luainessende silicate apatites according to the invention know all are made in a corresponding manner. the number of Heating tongue processes and the heating temperature are "on the reaction

109851/1811

-8- PHN. 4817 C.

speed of the starting mixture used. In addition to carbonates, oxides or, if heated, oxides can also be used in the starting mixture supplying compounds are used. The heating atmosphere can be neutral or oxidizing. If the phosphor contains tin, that is Heating atmosphere, preferably reducing. X-ray analyzes have shown that the silicates produced in this way all have the apatite crystal structure.

The results of measurements on luminescent silicate apatites according to the invention are mentioned in Table I below the formula Me ₂ -Me ₉ ( ^Si0 4) 6 ° 2 » ^Sb o 2 ^ents P ^rechen » where different elements are used for Me and Me «The table shows the light output (! .Α.) when excited with the radiation of a Low-pressure mercury discharge compared to the above-mentioned standard, the absorption of ultraviolet radiation and the position of the maximum of the emission

in spectrum (Λ ^) sax

109851/1811

PHN. 40; 7 C.

TABLE I.

Me ^τΙ Mo, ¹¹¹
a D L.A. Section ^A max ^Ca 2 ^Y 8 136 74 450 ^Sr 2 ^Y 8 109 84 435 «« 2 ^Y 8 67 70 460 Approx ₂ La ₈ 58 57 528 Sr ₂ La ₈ 101 65 535 Ba ₂ La ₈ 46 87 - Ca ₂ Y ₄ La ₄ 78 88 480 ^Sr 2 ^Y 4 ^La 4 88 88 485 CaSrY ₈ 123 80 445 CaMgY ₈ 102 80 445 CaZnY ₀
O 51 78 440 CaCdY _n 65 82 455 CaSrLa ₈ 68 86 540 SrBaLa ₀
O 60 82 540 CaSrY.La.
4 4 86 91 480

Table II gives the results of measurements on fabrics of the invention, in which the silicon is partly replaced by germanium and that of the formula

correspond, again.

109851/1811

PHN. 4817

TABLE II

L, A. Section P. 102 86 0 104 91 1.2 89 85 1.8 75 86 3 65 86 4.2

Table III gives a summary of measurements on luminescent silicate apatites according to the invention, in which various activators are used and those of the formula?

correspond.

TABLE III

Me ¹¹ Me? ¹¹
a D ^Pb 0.2 1 L.A. Section Λ Max ^Ca 1.86 ^Y 7.44 ^Pb 0.2 1 72 89 355 ^Sr 1.86 ^Y 3.72 ^La 5.72 ^ 0.2%, 40 95 320 ^Ca 1.86 ^Y 7.44 ^Pb o, 2 ^Ifa o, 65 91 355 , 585 ^Sr 1.86 ^T 3.72 ^La 3.72 ^Sn 0.2 46 92 320 , 585 ^Sr 1.86 ^La 7.44 65 66 495

Table IV gives the results of measurements on one Number of substances according to the invention activated with antimony as different] Values for the ratio b / a and with different antimony contents. In addition, some substances are mentioned in this table that contain antimony and

109851/181 1

PHN. 4C7

Manganese are activated. In the emitted radiation of the latter substances the manganese band is stronger, depending on the greater the manganese content.

TABLE IV

formula L.A. Section ^Sr 2.75 ^La 6.2 < ^Si V6 ° O 05 ^{? Sb} 0.1 74 61. ^Sr _2f 6 ^La 6.5 ( ⁵¹ Vo ⁰ O ^ ^Sb o, i 77 65 ^Sr 2,3 ^La 7, i ^(SiO 4 ⁾ 6 ° O, 95 ^{5 Sb} O, i 97 78 ^Sr 2.9 ^La 6.23 ^(SiO 4 ⁾ 6 ^O O, 25 ^{i Sb} 0.1 57 64 ^Sr 2.9 ^La 6.57 ^(SiO 4 ⁾ 6 ° 0.75 ^{i Sb} 0. i 59 73 ^Sr 2.9 ^La 7, O6 < ^SiO 4> 6 ^O 1.5 ^{; Sb} O, 1 45 58 ^Sr 2.9 ^La 7.23 ^(SiO 4 ⁾ 6 ° 1.75 ^{i Sb} 0.1 43 62 ^Sr 2.1 ^La 7.5 ^(SiO 4 ⁾ 6 ° 1.35 ^{i Sb} O, 1 96 81 "" 1.9 ^ .56 ¹⁸¹ VeVaS ^{1 Sb} o, 2 121 88 ^Sr i, 9 ^La 7.23 ^(SiO 4 ⁾ 6 ° O, 75 ^{i Sb} O, i 120 86 ^Sr 1.9 ^La 7.23 ^(SiO 4 ⁾ 6 ° 0.75 ^{i Sb} 0.2 117 86 ^Sr ,, 9 ^L * 1.56 ( ^Si % h °, _t 2 $> ^Sb O, 1 113 85 ^Sr i, 63 ^Ba o, i9 ^Ca o.i9 ^La 7.23 ^(siO 4 ⁾ 6 ° o, 85 ^{l Sb} o, i 100 83 ^CaY e ( ^Si0 4) 6 ^{0} Sb} O, 2 105 55 ^Ca 1.95 ^Y 7, e ( ^SiO 4 ⁾ 6 ° 1.65 ^{? Sb} O, 2 133 68 ^Ca 1.9 ¹ T ^ i ⁸¹ Ve ⁰ LJ ' ^Sb O, 2 133 67 ^C * 1.8 ^Y 7.2 < ^Si0 4> 6 ° 0.6 ' ^Sb 0.2 132 69 ^Ca 1.9 ^Y 7, e ( ^Si V6 ° 1.6 '^ 0.2 ¹⁶¹ OfO ₅ 129 69 ^Ca 1.85 ^T 7.8 ^(Si0 4> 6 ° ^1.55! ^ 0.2 ¹ S ,! 123 70 ^ΟΑ 1.8 ^Υ 7.8 ^ ^1Ο 4> 6 ° 1.5 ^{! Sb} O, 2 ^te O, 15 115 71 ^ Ι, Τί ^ .βί ⁸¹ Ve ⁰ I ^ ¹ ^ 0.2 ¹⁰¹ Of ₂ 110 74 ° Ί, Λ, β ( ^81ο Λ ^ο ι, 4 ^! ^ 0.2 ¹⁶¹ Of ₂₅ 102 75

10 9 8 51/1811

PHiT. 4817

Table V gives a summary of measurements on luminescent silicates according to the invention in which the silicon is used Part is replaced by phosphorus. It appears that with these phosphors Luminous yields can be achieved which are higher than those of the corresponding phosphors which do not contain any phosphor.

TABLE V

formula I ⁰ I. , 75 ' ^Sb 0.2 L.A. Section ^Ca 2, OO ^Y 7, f 0 ° 1 , 75 ' ^Sb 0.2 148 81 ^Ca 2.9O ^Y 6, i 5 ^ ¹ Vi, 0 ° 1 , 70; ^ 0.2 ¹¹¹¹ O ₁ O ₅ 138 82 ^Ca 2.85 ^Y 6 < 5, O ^(PO 4 ^} 1, O ⁰ I. , 50 ' Sb _{0 (2} Mn _{0. 25,} 113 87 ^Approx 2.65 ^r 6, i _5fO (K> ₄ ) _{1e 0} (P o ₄ ) ₃ , O ° 1.75 ' ^Sb 0.2 85 85 ^Ca 4,9O ^Y 4i * 3, O ^(PO 4 ⁾ 3, O ⁰ I. , 75 ' ^sb o! ₂ 76 74 2.0 < ^W 4> 4. o ^(G e0 ₄ ) 1, O ° 1.75 ^{J Sb} o, 2 66 76 30 < ⁸ⁱ V A ^ O Δ, ι # 5 ⁰ O ^Sb 0.2 89 87 ? 0 ^(Si0 4> 5 ° 1 , 75 ' ^Sb 0.2 65 79 > 0 ^{(Si (} V 5.5 (PO ₄ ) O, , 5 ° 1.75 ' ^Sb 0.2 115 64 _{? o} (sio ₄ ) , 1 ° 1.02 ^{J Sn} 0.2 89 84 _{? 0} (Si0) ^ 5.9 ^(P0 4> 0 , 5 ° 1.02 ^{1 Sn} 0.2 76 85 55.5 ^ 4 ⁵ O 0 ° 1 , 30 ' ^Pb 0.2 83 83 ^Approx. 2.90 ^Y 6, < 5.0 < ^W 4> 5. 51 79 ^Ca 5,4O ^T 4, i ^Sr 2,4O ^Y 7 ,, ^Sr 2.40 ^La 7 ^Sr 1.96 ^La 7 ^Sr 2.36 ^La 6, ^Sr 4.90 ^Y 4, ( ) 0 ^(si0 4> lo ( ^SiO 4> , 40 ^(Si0 4 , 34 ( ^Si0 4 94 ^(S10 4 io ( ^SiO 4 ⁾

109851/1811

Claims (1)

-13- PHN. 4817 C. P ATENT CLAIMS t 1. Phosphor with a luminescent silicate or one several alkaline earth metals and of lanthanum and / or yttrium, which Silicate has the apatite crystal structure, characterized in that the silicate of the form ?. Me ¹¹ Me ^ ¹¹¹ CSiO.). (PO.) (GeO.) OjA a + y by V 4'6-yp ^x 47 4 P x Q. corresponds, in which Me at least one of the elements Ca _; Sr, Ba and Mg, where up to 50 mol $ of the mentioned elements can be replaced by Zn and / or Cd, and in which Me furthermore represents at least one of the elements La and Y, and A is an activator from the group Sb, Pb, Represents Sn, Sb and Mn, where A replaces an equivalent amount of the elements Me and / or Me, while the following conditions are still met: a + 1.5b- 12 + χ 0 Ä χ £ -2 Od-p ^ 4.5 y + Ρ-ό. 4.5 0.05 <£ q ^ 0.8 and 4/3 ^ l b / a £ ⁸ »where, if y - 0, then 2 ^; b / a ώ 8, if a is £ 2, then: a + b ^ is 8.66, if a- £ r is 2, then a + b is £ 10, and if both a + b ; £ r 9 as well as χ - 0, y is 6: 1.5. .2. Phosphor according to claim 1, characterized in that Me essentially represents Ca and / or Sr, that A is an element of the group Sb, Pb, Sb and Mn, Pb and Mn, and that 0 ^ ρό3 and 0.1 £ y ^ 1.5 are. 3. phosphor 'according to claim 1 or 2, characterized in that 109851/1811 -H- that 3.5 5% b / a <4.5. 4. phosphor according to claim 3, characterized in that that b / a = 4. 5. Use of a phosphor according to one of claims 1 to 4 i ^ i a luminescent screen of a low-pressure mercury vapor discharge lamp. 10 9 8 51/1811