DE2500317A1 - Photochromic tellurite glass having controllable half-life - contg. oxides of tellurium erbium, lead or tungsten and pref. ytterbium - Google Patents

Abstract

Photochromic glass contains, by wt., 35-85 % TeO2, 0.5-10 % Er2O3, 0-30 (7-30) % PbO and/or 0-45 (15-40)% WO3, provided that PbO and WO3 contents are not both 0%. Used for modulation of radiation of wave-length near 479 nm, e.g. lasers; laser material carriers; optical data processing for electronic computers; flash light protection. Photochromic effect of desired magnitude and half-life time can be achieved by adjusting Er2O3 concn. In addn. to Er2O3, photochromic glass may contain a further suitable oxide of lanthanide series to modify photochromic effect, pref. 0.5-10 % Yb2O3 which acts as activator for Er2O3.

Description

Photochromic Glass The invention relates to photochromic glass, the manufacture of photochromic glass and the use of such glass.

A photochromic glass enjoyment of the present invention has tellurium oxide, Erbium oxide and at least one of the group consisting of lead oxide and tungsten oxide selected oxide.

The glass can also contain lead oxide and tungsten oxide together.

The proportion of erbium oxide (Er203) can expediently between approximately 1/2 wt.% And about 10 wt.% Lie.

The proportion of tellurium oxide (TeO2) can expediently between approximately 35 wt% and about 85 wt% are.

The weight fraction of lead oxide (PbO) can be between approximately 0% and approximately 30% and the proportion by weight of tungsten oxide (W03) can be between approximately 0% and approximately 45%, provided that these proportions are not simultaneous Can be zero, the proportion by weight of PbO can expediently between approximately 7% and about 30% and the weight fraction of WO3 between about 15% and about 40% lie.

In addition to Er203, the photochromic glass can be another suitable oxide of the rare earth metals of the lanthanide series contain to the photochromic Modify the effect of the glass.

Some rare earth metal oxides suppress, as detailed later executed, the photochromic effect of the glass according to the invention completely. These Oxides are therefore not and should not be suitable oxides of the rare earth metals therefore cannot be used for glass according to the invention.

The other suitable rare earth oxide can e.g.

Be ytterbium oxide. The weight fraction of ytterbium oxide (Yb203> can conveniently be between about 1/2% and about 10%.

If the glass is one or more such other suitable oxides of the contains rare earth metals, the weight fraction of the sum of such should be further Oxide or such Oxides of the rare earth metals and Er203 expediently be less than about 15%.

Smaller proportions of some additives that are normally used in glass production can be used, if desired, in the photochromic of the present invention Glass can be used to change the quality of the glass and / or the manufacture of the glass to facilitate.

However, some of these additives have an influence on the photochromic Effect that is created by the glass according to the invention. It should therefore Considerable care in the selection of the additive and with regard to the weight percentage at least some additives that are used are tanned.

Examples of some additives that can be used to make to improve the quality of the glass are: CeO2, MoO3, Nb205, CdO, Ta205, ZnO, ThO2, ZnF2, BaO, GeO2, B203, MgO, ZrO2 and SiO2.

Examples of other additives that can be used are: V205 'CuO, Mn203, P2O5, As203, U02, Li20, TiO2, SeO2 and Na2O.

In addition, the present invention relates to a method for Production of a photochronous glass, in which initially a mixture of tellurium oxide, Erbium oxide and at least one of lead oxide and tungsten oxide group selected oxide is formed, the components of the mixture in each other are in such a relationship that their proportions are within the glass-forming area lie, and at which the mixture is heated to its melting temperature.

The mixture can be heated in any suitable container, which withstands the melting temperature without contaminating the glass.

The mixture can suitably be brought to a temperature of about 950 to 10000C in air.

The melt can preferably be in a suitable preheated form poured and tempered in a suitable manner.

In this process, at least one other suitable one can be added to the mixture Oxide of the rare earth metals of the lanthanide series are introduced alongside Er203.

If such a further suitable oxide or such further suitable Rare earth metal oxides should be the sum of the weight fraction of such a further oxide or such further oxides of the rare earth metals plus Er203 must be less than 15%.

In the process, a smaller proportion of at least one suitable common additive commonly used in glass production will be introduced in order to modify the quality of the glass and / or the manufacture of the glass to simplify.

The invention also extends to a photochromic Glass, produced by this process.

A phtochrome glass is a glass that contains active ions, which can be stimulated to a higher metastable level, from which further Absorption transitions to even higher levels are possible.

Various glass systems that contain Er203 absorb radiation of 479 nm when optically excited with selected wavelengths in the near infrared creating a photochromic effect.

It is believed that the absorption of a metastable Level of the Er3 + ion. The metastable 4I13 / 2 state, which is approximately 6480 nm-1 is above the 4I15 / 2 ground state is indirectly through a combination of Absorption and subsequent cascade processes (radiation processes and collision processes) occupied by higher levels. The two main contributors to this Processes are as follows: 1. By absorbing radiation with a wavelength from about 1500 nm the metastable 4I13 / 2 state becomes directly from the 4I15 / 2 ground state occupied.

2. By absorbing radiation with a wavelength of approximately 970 nm the 4I state is occupied by the 4115/2 ground state. Through radiation processes 4 and collision processes, the 4I11 / 2 state drops to the metastable I13 / 2 state and contributes to its occupation.

The 479 nm absorption feature (which is referred to as the photochromic effect) is believed to be one Transition in the trivalent erbium ion.

Under pulsating excitation conditions, the relaxation properties of the metastable state by checking the change in absorption «(t) at the relevant one photochromic wavelength (479 nm) can be determined before and after the light flash pulses. This follows from Beer-Lambert's exponential absorption law.

The following applies: whereby = Change in absorption at 479 nm at a time t after the excitation light flash = intensity of the transmitted light at the photochromic wavelength of 479 nm at a time t after the excitation light flash = intensity of the transmitted light at the photochromic wavelength of 479 nm without the excitation light flash d = path length in the sample.

In the following description, the expression [# α (@)] # will be used used to maximize the photochromic effect at the wavelength Identify i after a flash of light.

A xenon flash tube can advantageously be used as an excitation or pump source can be used as it has a wide range. It will, however noted that any other suitable pump source can be used, the one Radiation with a wavelength of 1500 nm (bandwidth approximately 60 nm) and / or 970 nm (bandwidth approximately 60 nm), e.g.

a laser that emits one of these wavelengths.

The photochromic glasses of the present invention are now exemplified with reference to various experiments which have been carried out, shown.

The US-PS 3,664,725 discloses the photochromic effect in silicate, Borate, phosphate and germanate glass systems doped with Er203.

As a result of the experiments carried out with the glass systems of this US Pat have been carried out, it has been found that the photochromic effect of the silicate glass systems much more pronounced than that of the borate, phosphate and germanate glass systems, endowed with Er203 is. With the Borat, Phosohat and GermanFoGlass systems the photochromic effect was detectable, but almost negligible.

About the more pronounced photochromic effect and the reduced half-life effect to illustrate which with the photochromic glasses of the present invention in Relation to the glass systems disclosed in the above-referenced U.S. Patent can be achieved, experiments with erbium-doped silicate glasses have also been carried out from the previous Reasons stated in paragraphs. The results were compared with the results obtained with the photochromic Glasses of the present invention have been achieved.

For these experiments, samples were made by introducing 3+ Er ions as Er203 in tellurite basic glasses, which belong to the glass-forming area Concentrations of 0.5 to 15 wt.% Er203 produced.

The samples were made by melting batches of 25 or 100 g in Hard-fire porcelain crucibles made in air at temperatures between 950 and 10000C. The batches were stirred with silica rods during the melting process.

It has been found that the melting process is very rapid and normal was completed in less than 10 minutes.

It was possible to produce clear glasses with 15% by weight Er203.

In this case, however, the melting process was considerably slower than for melts with 10 wt.% Er203.

The comparison samples were made by introducing Er3 + ions as Er203 in a silicate base glass with concentrations of 1 to 16 wt.% Er203. The silicate matrix consisted of the network former SiO2 and modifier Nu20, LiO2 and K20. Four additional compounds (BaO, ZnO, Sb203 and Al203) were added, to improve the quality of the glass.

It has been found that it is impossible to use more than 16 wt% Er203 to introduce into the special glass.

The silicate samples were placed in pure aluminum pans at a temperature melted and stirred in the range from 1520 to 15800C.

After each sample was formed, it was finally reduced to one Size from 40mm to 35mm to 7 with cut and polished.

The compositions of typical samples used for the experiments are listed in Table 1. Table 1% by weight Er2O3 0.5 1.2 2 3 4 6 10 15 1 2 4 6 8 10 14 16 TeO2 49.7 49.2 49.0 48.4 48.0 47.0 45.0 42.5 PbO 19.9 19.8 19.6 19.4 19.0 18.8 18.0 17.0 WO3 29.9 29.8 29.4 29.2 28.8 28.2 27.0 25.5 SiO2 62.5 62.5 62.5 62.5 62.5 62.5 62.5 62.5 Na2O 10.6 10.6 10.6 10.6 10.6 10.6 10.6 10.6 LiO2 0.9 0.9 0.9 0.9 0.9 0.9 0.9 0.9 K2O 9.6 9.6 9.6 9.6 9.6 9.6 9.6 9.6 BaO 7.25 7.25 7.25 7.25 6.0 4.0 1.5 -ZnO 2.25 2.25 2.25 2.25 1, 5 1.5 - -Sb2O3 0.9 0.9 0.9 0.9 0.9 0.9 0.9 0.4 Al2O3 5.0 4.0 2.0 - - - - -Probe TW TW TW TW TW TW 430 431 No. 19 S 22 S 3 S 5 S 17 S 18 S A4 A1 A2 A3 A5 A6 A33 A34 the Experiments were then carried out on the samples by optically pumping the samples with a linear xenon flash lamp in a cylindrical recess parallel to the longitudinal axis the sample was mounted. Between the flash lamp and the sample was a protective glass plate of 1 mm thickness is arranged. The flash light energy became constant held at 450 joules with a flash duration of 2 milliseconds. The absorption of the samples at the wavelength of 479 nm was obtained by using a xenon arc lamp, a suitable monochromator arrangement and a storage oscilloscope. The test steel with a width of 0.5 mm and a height of 2 with was passed through the Center and sent along the longitudinal axis of the sample.

The relative beam intensity was displayed at intervals read 2 milliseconds after the flash.

The time dependence of the change in absorption # α (t) at the Wavelength of 479 nm was then calculated for the various samples. Graphic Representations were made and the half-lives from these representations read. The half-life of the effect was taken as the time which between the maximum value obtained by each particular sample and half the maximum value passed.

The results obtained in these experiments are for example shown in FIGS.

1 and 2 show typical graphical representations of the change in absorption ß K (t) compared to the time after the Flash passed for Sample TW 22 S of Table 1 and Sample A6 of Table 1. These graphs Representations were found to be typical of all samples and illustrate the exponential Waste form; Fig.3 is a graph showing the size of the photochromic Effect at the wavelength of 479 nm, which is caused by the maximum value of the change in absorption [# α (o)] 479 versus wt.% Er203 is shown for the tellurite and Compares silicate glass samples of Table 1; 4 shows a graphic representation, which is the decrease in the half-life of the change in absorption da (t) at a wavelength of 479 nm for the tellurite and silicate glass samples of Table 1, and 5 shows a graphic representation of the influence of different Er203 concentrations in the tellurite and silicate glass samples in Table 1 to the logarithm of the half-life the photochromic effect at a wavelength of 479 nm.

With regard to the experiments which were carried out with those listed in Table 1 Samples have been carried out as shown in Figures 1 to 5, it is noted that the highest value of the photochromic effect L <0> J479 at 2 wt.% Er203 in the tellurite glass of the present invention a maximum and at 15 wt% Er203 reached a minimum. The maximum value in the silicate glass samples used in the present Invention used for comparison is achieved at 10 wt.% Er203 and is considerably lower than the maximum value in the tellurite glass sample with 2 wt.% Er203.

It is further noted that the maximum value at 2 wt.% Er203 in the tellurite glass of the present invention is more than twice larger than that of that Silicate glass with the same percentage by weight of Er203 is.

From the graphs of the logarithm of the half-life compared to the wt.% än Er203 for the tellurite and silicate system (Fig.5) further shows that they are linear and have obviously identical negative slopes exhibit.

However, the curve of the tellurite system has a smaller ordinate section than the silicate system.

The following approximate relationships can be established from the results become: In T1 = -0.15 W + 1.26 for the tellurite system 2 and In T1 = -0.15 W + 2.72 for the silicate system, T1 where ß is the half-life of the effect in milliseconds and W is the weight percentage of Er203 in the system samples.

From the experiments carried out, it was found that the photochromic Effect in the majority of samples in the glass-forming area of the tellurite system was present. The photochromic effect increased as the concentration of Er203 increased peaked and then fell. At an Er203 concentration of more than 10% by weight, the photochromic effect was very small, and in some cases nearly extinguished.

For all samples in the glass-forming area of the tellurite system, which show the photochromic effect, it was found that the half-life the effect decreased exponentially with increasing Er203 concentration.

It is an advantage of the embodiments of the invention shown in FIG Table 1 shows that by adjusting the Er203 concentration within of the limits indicated, a photochromic effect of a desired size photochromic effect of a desired half-life or a desired one Balance between these two for various uses of the present Invention can be achieved.

In further experiments carried out with the photochromic glasses of the present Invention have been carried out, the maximum value of the photochromic effect became measured, with further oxides of the rare earth metals of the lanthanide series, at the same time only one at a time, to a tellurite glass system with 2 wt.% Er203 and a constant Weight ratio of 50 TeO2: 20 PbO: 30 W03 were added. Whether it was 203 the only rare earth metal oxide that increases the photochromic effect. All other oxides of the rare earth metals of the lanthanide series dampen the photochromic Effect at a wavelength of 479 nm or do not influence it in any way.

Ytterbium oxide therefore acts as an activator for erbium, creating a photochromic effect of increased size is caused.

To achieve the photochromic effect in a tellurite glass system with 2 wt. % Er203 and a constant weight ratio of 50 TeO2: 20 To increase PbO: 30 W03, Vb203 can be added. As shown in Figure 6, was able to achieve a maximum value of the photochromic effect in the glasses of the present one Invention with a concentration of 2 wt.% Er203 and a concentration of 2% by weight of Yb203 can be achieved. The reason for the increased effect is energy transfer from the first 2F5 / 12 excited state of the Yb3 + ion to the second excited 1112 state of the Er3 + ion in the tellurite glass and the occupation of the 4113/2 metastable State due to radiation processes and collision processes from the 4I11 / 2 state. The half-life of the effect is not influenced by the addition of Yb203 and remains constant at the value which for a tellurite glass sample with 2 wt.% Er203 and no other rare earth oxide has been obtained.

By adjusting the concentration of Er203 and the concentration at Yb203 the size of the photochromic effect and the half-life of the effect within the indicated limits in an advantageous manner for special applications of the present invention.

To the influence of the addition of further oxides of the rare earth metals the lanthanide series to tellurite glass with 2% by weight Er203 and 4% by weight Yb203 to determine the maximum value and the half-life of the photochromic effect at a wavelength of 479 nm for samples, which in each case 1% by weight is rare Earth metal had been added, measured. To maintain a constant weight ratio From 50 TeO2 to 20 PbO: 30 W03, the actual weight percentages were used held constant with 46.5% by weight TeO2, 18.6% by weight PbO and 28.2% by weight WO3. the Results are summarized in Table 2.

Table 2 Rare earth # α (o) at 479 nm T metal oxide in mm-1 ½ (ms) La2O3 0.0603 4.0 Tb203 0.0507 4.0 Y203 0.0448 3.8 Gd2O3 0.0343 4.4 Lu203 0.0294 4.0 Eu203 0.0058 0.6 Ho203 0.0046 1.0 Nd203 0 Sm203 0 Tm203 0 Ce203 0 Dy203 0 In each case in which 1% by weight of oxide of a rare earth metal is added to a glass of the tellurite system of the present invention with 2% by weight Er203, 4% by weight Yb203 and TeO2, PbO and W03 has been added in the ratio of 50:20:30 the photochromic effect at a wavelength of 479 nm and weakened in some Cases have been suppressed. The half-life is by the addition of Y203, Eu203 and Ho203 and increased by the addition of Gd203.

In those cases in which the effect is achieved by adding 1% by weight of a rare earth metal, namely Nd203, Sm203, Tm203, Ce203 and Dy203, suppressed the experiment was with samples with a reduced amount of oxide of the rare earth metal repeated. The results are summarized in Table 3.

Table 3 Rare Earth wt% PD ((O) at 479 nm 1 (ms) metal oxide in Nd2O3 0.1 0.0403 2.0 Tm203 0.5 0.0028 2.0 Sm203 0.5 0 Ce203 0.5 0 Dy203 0.5 0 It was therefore found that the addition of small amounts of Nd203 and Tm203 also the half-life of the photochromic effect at the wavelength decreased from 479 nm.

In the sample with 2% by weight Er203, 4% by weight Yb203 and 0.1% by weight Nd203 the effect is smaller than in a sample with no Nd203. This is a surprising one Effect, since it is known in the case of a similarly doped silicate glass that the Effect is increased by adding Nd203. The mechanism of energy transport from Nd203 to Yb203 and from here to Er203, which is present in the silicate glass is absent in the tellurite glass of the present invention.

From Tables 2 and 3 it is clear that some oxides of the rare earth metals of the lanthanide series for the photochromic glasses of the present Invention are not suitable and that some oxides of the rare earth metals only can be added in very small proportions.

With the photochromic glasses of the present invention with special Proportions of Te02, W03, PbO and a constant weight percentage of Er 203 were Further experiments were carried out to investigate the influence of the base glass on the photochromic Investigate effect. Representative samples were taken from the glass-forming area of the ternary system TeO2-PbO-W03 and selected as base glasses for doping used with Er203. The size and half-life of the photochromic effect in the Wavelength of 479 nm was found for each sample. The influence of the base glass This made it possible to determine the photochromic effect. The glass-making one Area in the ternary system Te02-Pb0-W03 from which the representative samples were selected is shown in Fig.7. In this diagram, A represent I represent the points with the selected matrix compositions. The weight ratios of TeO2, PbO and WO3 for these matrices are summarized in Table 4.

Table 4 Weight ratio of TeO2-PbO-WO3 sample point TeO2 PbO WO3 A 80 0 20 B 70 10 20 C 60 20 20 D 70 0 30 E 60 10 30 F 50 20 30 G 60 0 40 H 50 10 40 I 40 20 40 samples with different amounts of Er203 (e.g. 0.5 wt.%, 2% by weight, 4% by weight and 10% by weight %) were with base glass compositions A to I manufactured. The dependence of the size and the half-life of the effect on the Base lens composition is shown in histogram form in FIGS. 8 and 9.

In the base glass compositions B, C, E, F and H the photochromic reaches Effect at the wavelength of 479 nm relatively high values for given Er203 concentrations. The effect is low for glass compositions D and G.

In the case of basic glasses A to I, type D is used for the half-life the effect reaches a minimum. With species A and G the effect is too weak to enable a half-life determination.

The above results can be used to determine the composition of a Tellurite glass, which has the photochromic effect at the wavelength of 479 nm of a given size and half-life.

Example: To get a photochromic glass that has a relative strong photochromic effect and a short half-life at the wavelength of 479 nm, a glass sample with 2 wt.% Er203 and TeO2, PbO and W03 im achieved Weight ratio of 60: 10: 30 a size (t (0) at the wavelength of 479 nm) of 0.045 mm 1 with a half-life of 3 milliseconds. The addition of 4 Weight% Yb203 increases the size to approximately 0.07 mm-1 without affecting the half-life. The addition of small amounts of Eu203, Nd2O3, Ho203, Y203, Tm203 (less than 0.1 Weight%> would increase the speed of the effect without increasing the size significantly to influence.

In making the photochromic glass of the present invention It is believed that the shape of the crucible in which the glass is formed will be determined Can affect the quality of the glass. It is further believed that alumina have an adverse effect on the photochromic glass of the present invention can. In the manufacture of the photochromic glass according to the invention should therefore no alumina pans are used.

while the melting temperature of the photochromic glass is present Invention is significantly below the melting temperature of silica, it is assumed that the production of photochromic glass according to the present invention in silicate crucibles and the use of silica rods for stirring purposes to photochromic silica traces ii Glass of the present invention can lead. These traces of silica are evident here advantageous in making the photochromic glass of the present invention In silica crucibles with silica rods, the otiality of the glass is obviously improved.

The photochromic glasses of the present invention can be various Have applications.

The photochromic glass of the present invention is capable of modulation radiation of a wavelength close to 479 n1 can be used. Binige Embodiments of the present invention, in particular those which have a can have great photochromic effect and a short half-life for the rapid modulation of radiation can be used, e.g., tuned dye lasers or another type of laser, pulsed or continuous high-intensity radiation emits with a wavelength of about 1500 na or 970 nm, can be used to "darken" of the photochromic glass sample at the wavelength of 479 na can be used for one Period of time with a half-life equal to that of the effect in the particular Sample. The 479 nm radiation from a continuous or pulsed light source (e.g. the 479 nm argon laser beam o peeente) can be modulated. In addition, you can some embodiments have application as laser material carriers and also in in reference to Q-shift and possibly for self-Q-shift for laser beams. Optical data reading systems for electronic computers, which the storage and readout of data in a volume of the photochromic material can possibly represent a further area of application. With some Embodiments of these materials can store two-dimensional holograms and then read out. Flash protection for high intensity light can through a glasses assembly with the photochromic material and a filter that which transmits 479 nm radiation with a bandwidth of approximately 5 nm provided that the flash of light contains the pump wavelengths. Upon receipt The photochromic material will darken after the flash. That between the Eye (or other detector) and the photochromic material arranged pilter only the reduced radiation intensity of the wavelength 479 + 5 nm is transmitted, thereby protecting the eyesight from radiation damage or the detector from overexposure is slotted.

Claims (17)

Claims 1. Photochromic glass, thereby g e k e n n n z e i c h -n e t that it Tellurium oxide, erbium oxide, and at least one of lead oxide and tungsten oxide Has group selected oxide. 2. Photochromic glass according to ClaimX1, characterized in that it is -k e n n z e i c Note that the weight fraction of erbium oxide is between about 1/2% and about 10%. 3. Photochromic glass according to claim 1 or 2, characterized in that g e -k e n n it is noted that the proportion by weight of tellurium oxide is between approximately 35% and is about 85%. 4. Photochromic glass according to one of claims 1 to 3, characterized g e it is not stated that the weight fraction of lead oxide is between approximately 0% and about 30% and the weight fraction of tungsten oxide between about 0% and is about 45% on condition that they are not 0% at the same time. 5. Photochromic glass according to claim 4, characterized in that g e k e n n -z e i c It should be noted that the proportion by weight of lead oxide is between approximately 7% and approximately 308 and that the proportion by weight of tungsten oxide is between about 15% and about 40%. 6. Photochromic glass according to one of claims 1 to 5, characterized g e no indication that there is at least one other suitable oxide of the rare Earth metals of Has lanthanides next to erbium oxide, to modify the photochromic effect of the photochromic glass. 7. Photochromic glass according to claim 6, characterized in that g e -k e n n z e i c h n e t that the weight fraction of the sum of erbium oxide and any other suitable Lanthanide series rare earth oxide is less than about 15%. 8. Photochromic glass according to claim 6 or 7, characterized in that g e -k e n n notices that the other suitable oxide of the rare earth metals of the lanthanide series Is ytterbium oxide. 9. Photochromic glass according to claim 8, characterized in that g e k e n n -z e i c Note that the weight fraction of ytterbium oxide is between about 1/2% and about 10%. 10. Photochromic glass according to one of claims 1 to 9, characterized in that g It is not noted that there is a small proportion of at least one suitable conventional additive that is used in glass production, contains to the Change the quality of the glass. 11. A method for producing a photochromic glass, thereby g I do not know that initially a mixture of tellurium oxide, erbium oxide and at least one selected from the group consisting of lead oxide and tungsten oxide Oxide is formed, with the components of the mixture within a glass-forming Area lie, and that the mixture is heated to its melting temperature. 12. The method according to claim 11, characterized in that g e k e n n -z e i c h n e t that the mixture is at a temperature of between about 9500 and about 10000C in air. 13. The method according to claim 11 or 12, characterized in that g e -k e n n z e i c h n e t that the proportion by weight of erbium oxide between about 1/2% and about 10%, the weight fraction of tellurium oxide between about 35% and about 85%, the Weight fraction of lead oxide between approximately 7% and approximately 30% and the weight fraction of tungsten oxide is between about 15% and about 40%. 14. The method according to any one of claims 11 to 13, characterized g e k e It is not indicated that there is at least one further suitable oxide in the mixture of the rare earth metals of the lanthanide series is introduced alongside erbium oxide, to modify the photochromic effect of the glass. 15. The method according to claim 14, characterized in that g e k e n n -z e i c h n e t that the other suitable oxide of the rare earth metals of the lanthanide series Ttterbiuaoxid is. 16. The method according to claim 15, characterized in that it is e k e n n -z e i c h n e t that the relative proportions of erbium, oxide and ytterblumoxld create a photochromic glass that has a photochromic effect within the given limits having a desired size and half-life. 17. The method according to any one of claims 11 to 16, characterized g e k e n n n z e i n e t that in the mixture a small proportion of at least one appropriate conventional additive used in glass manufacture is used to simplify the formation of the glass or to increase the quality of the glass change.