LEAD-FREE CRYSTAL GLASS WITH THE REFRACTIVE INDEX HIGHER THAN 1,52

Abstract: Lead-free cyrstal glass with the refractive index higher than 1,52, designated for the production of man-made and machine-made utility glass especially of luxurious character with high light transmittance, perfect clearness and elevated hydrolitical resistance which is suitable particularly for decorating by cutting, engraving and other decorating techniques and is well polishable by using both chemical and mechanical processes, containing in % by weight from 50 to 75 of silicon dioxide SiO2, from 0,05 to 10 of aluminium oxide Al2O3, from 0,05 to 15 of zirconium dioxide ZrO2, from 0,001 to 2,5 of hafnium dioxide HfO2, from 0,001 to 5 of titanium dioxide TiO2, from 2 to 9 of calcium oxide CaO, from 0,001 to 6 of magnesium oxide MgO, from 0,05 to 10 of zinc oxide ZnO, from 0,1 to 10 of potassium oxide K2O, from 5 to 16 of sodium oxide Na2O, from 0,05 to 2,5 of entimony trioxide Sb2O3 and the total amount of iron expressed as iron trioxide Fe2O3 ranges from 0,005 to 0,035 % by weight, while this glass further contains in % by weight from 0,001 to 1,25 of sulphates SO4<2-> and chlorides Cl<-> and from 0,000005 to 0,8105 at least one component from the group comprising erbium oxide Er2O3, neodymium oxide Nd2O3, ceric oxide CeO2, cobaltous oxide CoO, nickel oxide NiO, manganese oxides and selenium compounds. In any case, sum of all components mentioned totals at lest 99,6 % by weight.

Description: Lead-free crystal glass with the refractive index higher than 1 ,52 Technical field This invention relates to lead-free crystal glass with the refractive index higher than 1,52 which is intended for the man-made and machine-made utility glassware, especially those of luxurious character, with high lustre and light transmittance. The glass contains silicon dioxide Si0 2 , aluminium oxide A1 2 0 3 , zirconium dioxide Zr0 2 , hafnium dioxide Hf0 2 , titanium dioxide Ti0 2 , calcium oxide CaO, magnesium oxide MgO, zinc oxide ZnO, potassium oxide K 2 0, sodium oxide Na 2 0, antimony trioxide Sb 2 0 3 , iron trioxide Fe 2 0 3 , sulphates, chlorides and at least one component from the group incorporating erbium oxide Er 2 0 3 , neodymium oxide Nd 2 0 3 , eerie oxide Ce0 2 , cobaltous oxide CoO, nickel oxide NiO, manganese oxides and selenium compounds. Background art For the products from so called cheap crystal glass accentuated by a low price the refractory index fluctuates about a value of 1,51 and, barium oxide BaO and lead oxide PbO are being used by some manufacturers but in smaller amounts only, as was stated by A.Smrcek in the journal Sklήf a keramik 3ji , (1988), p. 286-294. The group of special crystal glass types represents already more refined products in which the refractive index is under control and has to be maintained close to the value 1,52. This can be achieved by addition of barium oxide BaO, zinc oxide ZnO and, as the case may be, in smaller amounts even of lead oxide PbO, as it was stated e.g. in DE-patent from 1987 No. 2839645, such a glass according to said patent contains in % by weight as follows: silicon dioxide Si0 2 65 to 75, aluminium oxide A1 2 0 3 0,1 to 2, calcium oxide CaO 2 to 12, magnesium oxide MgO 0 to 8, sodium oxide Na 2 0 7 to 15,potassium oxide K 2 0 0 to 10, lithium oxide Li 2 0 0 to 3. barium oxide BaO 1 to 6, zinc oxide ZnO 0,2 to 3, lead oxide PbO 0 to 10 and titanium dioxide Ti0 2 0,2 to 5.This invention covers by its chemical composition, with the exception of titanium dioxide Ti0 2 most of crystal glass of types being produced excepting of lead and high-lead crystal glass produced with the content of lead oxide PbO 1 24 % by weight. It is also necessary to refer to the published Japanese patent application from 1986 No. 61270234, though relating to glass types for fluorescent lamps, but with the composition analogous to crystal glasses. The glass types according to this invention contain in % by weight from 65 to 75 of silicon dioxide Si0 2 , from 1 to 2,5 of aluminium oxide A1 2 0 3 , from 0,001 to 0,02 of iron trioxide Fe 2 0 3 , from 10 to 18 of sodium oxide Na 2 0, from 0 to 2 of potassium oxide K 2 0, while the sum of sodium and potassium oxides ranges between 10 and 18, from 1 to 10 of calcium oxide CaO, from 0,5 to 6 of magnesium oxide MgO, while the sum of calcium and magnesium oxides ranges between 2 an 15, from 0,1 to 2 of barium oxide BaO, from 1 to 3 of boron oxide B 2 0 3 and 0,2 to 2 of antimony trioxide Sb 2 0 3 , while the sum of barium, boron and antimony oxides ranges between 1,4 and 6 % by weight. For the products of luxurious character which are decorated predominatingly by cutting the lead and high-lead crystal glass types are used where the refractive index value ≥ 1,545 is required.At the present time the unharmful hygienic properties of glass are being preferred particularly concerning the content of lead and barium in the leaching, as important also the purity of the atmosphere and effluents is regarded. With regard to the fact that in the production of those special crystal glass types the refractive index of the desired value is being elevated largely by an increased amount of lead oxide PbO and barium oxide BaO, the said hygiene properties that are required induce hardly solvable problems in the production of such glass types. The disadvantages mentioned will be improved according to published Czechoslovak patent application No. 1344-91 which corresponds to European patent application No. 92909183.3, the proposed chemical composition of crystal lead-free glasse s conforming with it contains in % by weight from 50 to 65 of silicon dioxide Si0 2 , from 0,1 to 10 of aluminium oxide A1 2 0 3 , from 0,5 to 17 of zirconium dioxide Zr0 2 , from 10 to 22 of potassium oxide K 2 0 and/or sodium oxide Na 2 0, from 2 to 10 of calcium oxide CaO and/or magnesium oxide MgO,and from 0,01 to 0,025 of iron trioxide Fe 2 0 3 , individually or in a combination it contains from 0,1 to 10 % by weight of barium oxide BaO, zinc oxide ZnO, boron oxide B 2 0 3 and lithium oxide Li 2 0 and traces to 1 % by weight of antimony trioxide Sb 2 0 3 . As further modifiers individually or in a combination titanium dioxide Ti0 2 and stannic dioxide Sn0 2 are present in the range of traces to 1 % by weight. The composition of a lead-free zinc-silicon crystal glass is presented also in the published patent application EP from 1991 No. 91121730.5. The glass according to this invention contains in % by weight from 65 to 70 of silicon dioxide Si0 2 , from 6 to 9 of calcium oxide CaO, from 4 to 12 of potassium oxide K 2 0, from 4 to 12 of sodium oxide Na 2 0, from 0,5 to 5 of boron oxide B 2 0 3 , from 4 to 7 of zinc oxide ZnO, from 0,1 to 1 of antimony trioxide Sb 2 0 3 and from 1 to 6 of zirconium dioxide Zr0 2 and/or titanium dioxide Ti0 2 . Zirconium dioxide Zr0 2 according to the published Japanese patent application from 1988 No. 63147843 can be used as a component also in a chemically resistent glass which composition in % by weight is as follows: from 63 to 67 of silicon dioxide Si0 2 , from 4 to 4,8 of boron oxide B 2 0 3 ,from 4 to 5,5 of aluminium oxide A1 2 0 3 , from 0 to 4 of titanium dioxide Ti0 2 , from 2,5 to 3,6 of magnesium oxide MgO, from 4,7 to 8,7 of calcium oxide CaO, from 0 to 5 of barium oxide BaO, from 7,5 to 13,9 of sodium oxide Na 2 0, from 0 to 2 of potassium oxide K 2 0, while the sum of sodium and potassium oxides ranges from 8 to 15,5, from 0 to 1 of iron trioxide Fe 2 0 3 and from 0 to 5 of zirconium dioxide Zr0 2 . The next group is composed of inventions, in which besides zirconium dioxide Zr0 2 also strontium oxide SrO is incorporated. This category according to the U.S. patent from 1977 No. 4065317 includes glasses with a high chemical resistance which are suitable for pharmaceutical purposes, scientific and biological branches. The composition of these glass types is as follows (in mol.%): from 75 to 82 of silicon dioxide Si0 2 , from 2 to 8 of zirconium dioxide Zr0 2 , from 1 to 5 of aluminium oxide A1 2 0 3 , from 2 to 10 of sodium oxide Na 2 0, from 2 to 10 of potassium oxide K 2 0, from 2 to 10 of calcium oxide CaO, from 2 to 10 of strontium oxide SrO, from 2 to 10 of barium oxide BaO, without boron oxide B 2 0 3 . According to the European patent application from 1991 No. 405579 strontium oxide SrO is used as a component also in packing glass with the composition as follows (in % by weight): from 45 to 70 of silicon dioxide Si0 2 , from 5 to 16 of zirconium dioxide Zr0 2 , with 10 to 30 of alkaline metal oxides, over 12 oxides of divalent metals, and over 5 oxides of trivalent metals, while as alkaline metals sodium Na, potassium K or lithium Li are being regarded, and magnesium Mg, calcium Ca, strontium Sr, zinc Zn or barium Ba being classified among divalent metals and aluminium Al , iron Fe or boron B among trivalent metals. Strontium oxide SrO acts as a component in packing glass also in USSR patent from 1972 No. 330119. The complete composition is as follows (in % by weight): from 68 to 73 of silicon dioxide Si0 2 , from 1,8 to 4,5 of aluminium oxide A1 2 0 3 , from 0,02 to 1,5 of iron trioxide Fe 2 0 3 , from 0,5 to 4 of magnesium oxide MgO, from 4 to 9,5 of calcium oxide CaO, from 2 to 5,2 of strontium oxide SrO, from 11 to 13 of sodium oxide Na 2 0, from 0,5 to 2 of potassium oxide K 2 0 and from 0,2 to 2 of zirconium dioxide Zr0 2 . According to the published Japanese application from 1976 No. 51055310 zirconium dioxide Zr0 2 is included in watch covering glasses, the composition of which in % by weight varies in the range between 4 to 10 of aluminium oxide A1 2 0 3 , 0 to 5 of magnesium oxide MgO, 10 to 20 of sodium oxide Na 2 0, 2 to 10 of potassium oxide K 2 0, 0 to 10 of boron oxide B 2 0 3 . The actual composition contains (in % by weight) : 65 of silicon dioxide Si0 2 , 4 of aluminium oxide A1 2 0 3 , 0,017 of iron trioxide Fe 2 0 3 , 0,55 of titanium dioxide Ti0 2 , 0,7 of magnesium oxide MgO, 3,96 of zirconium dioxide Zr0 2 , 0,65 of arsenic trioxide As 2 0 3 , 10 of sodium oxide Na 2 0, 9,5 of potassium oxide K 2 0, 3,62 of boron oxide B 2 0 3 and 3,92 of zinc oxide ZnO. The lead-free crystal glass types mentioned in the survey according to the Czechoslovak patent application No.1344-91 which corresponds to the European patent application No.92909183.3 are designated for the man-made and machine-made utility glassware of plain type or decorated by engraving, cutting and other decorative techniques. These glass types that are well polishable mainly by chemical processes are suitable above all for cutting by diamond tools. Disclosure of the invention This invention relates to the composition of crystal lead-free glass with the refractive index higher than 1,52 contains 50 to 75 % by weight of silicon dioxide Si0 2 , 0,05 to 10 % by weight of aluminium oxide A1 2 0 3 , 0,05 to 15 % by weight of zirconium dioxide Zr0 2 , 0,001 to 2,5 % by weight of hafnium dioxide Hf0 2 , 0,001 to 5 % by weight of titanium dioxide Ti0 2 , 2 to 9 % by weight of calcium oxide CaO, 0,001 to 6 % by weight of magnesium oxide MgO, 0,05 to 10 % by weight of zinc oxide ZnO, 0,1 to 10 % by weight of potassium oxide K 2 0, 5 to 16 % by weight of sodium oxide Na 2 0, 0,05 to 2,5 % by weight of antimony trioxide Sb 2 0 3 and total content of iron expressed as iron trioxide Fe 2 0 3 varies between 0,005 and 0,035 % by weight while this glass further contains 0,0001 to 1,25 % by weight of sulphates S0 4 2" and chlorides Cl~ and 0,000005 to 0,8105 % by weight of at least one component from the group including erbium oxide Er 2 0 3 , neodymium oxide Nd 2 0 3 , eerie oxide Ce0 2 , cobaltous oxide CoO, nickel oxide NiO, manganese oxides and selenium compounds. In any case the total of all these components is at least 99,6 % by weight. As impurities amounting maximum of 0,4 % by weight the compounds carried in above all by usual glass raw materials can be present such as strontium oxide SrO, lead oxide PbO, cadmium oxide CdO, cupric oxide CuO, arsenic trioxide As 2 0 3 , praseodymium trioxide Pr 2 0 3 , samarium oxide Sm 2 0 3 , chrome oxide Cr 2 0 3 , vanadic oxide V 2 0 5 , uranium trioxide U0 3 , thorium dioxide Th0 2 , fluorides, etc. Glass refining by antimony trioxide Sb 2 0 3 or if needed by antimonitans introduced usually into glass batch in common with nitrates will be more intensive at the presence of sulphates S0 A 2 ~ varying between 0,0001 and 0,75 % by weight and chlorides Cl " between 0,001 and 0,5 % by weight. High light transmittance and perfect clearness is achieved at the presence at least one component from the group comprising 0,0001 to 0,2 % by weight of erbium oxide Er 2 0 3 , 0,0001 to 0,2 % by weight of neodymium oxide Nd 2 0 3 , 0,001 to 0,2 % by weight of eerie oxide Ce0 2 , 0,000005 to 0,0005 % by weight of cobaltous oxide CoO, 0,00001 to 0,005 % by weight of nickel oxide NiO, 0,001 to O.200 % by weight of manganese oxide Mn0 2 expressing in re-count manganese oxides and, selenium amount of 0,00001 to 0,005 % by weight, expressing in re-count selenium compounds. Utility and technological properties particularly the meltableness and partly also the refractive index of glass, its chemical resistance and the liquidus temperature are advantageously modified by at least one oxide from the group comprising 0,05 to 6 % by weight of barium oxide BaO, 0,001 to 5 % by weight of boron oxide B 2 0 3 , 0,001 to 1,5 of phosphoric oxide P 2 0 5 and 0,001 to 1,5 % by weight of lithium oxide Li 2 0. As further modifiers, with the respect to the refractive index, partly to the mean dispersion and to the surface tension, this glass can contain with advantage at least one oxide from the group comprising 0,05 to 5 % by weight of stannic dioxide Sn0 2 , 0,05 to 2 % by weight of lanthanum oxide La 2 0 3 , 0,05 to 10 % by weight of bismuth oxide Bi 2 0 3 , 0,001 to 0,1 % by weight of molybdic oxide Mo0 3 and 0,001 to 0,5 % by weight of tungstic oxide W0 3 . Among dominant advantages of this glass type belong good cutting and engraving abilities, namely by diamond, carborundum, electrite, etc. tools, good polishing ability by using both chemical and mechanical processes, excellent optical properties, especially high light transmittance and perfect clearness. From the point of view concerning crystal glass types its excellent chemical resistance is also of importance and as favourable the comparable or more advantageous melting, refining, forming and cooling temperatures and also convenient crystallization properties can be regarded. But its major preference consists in the absence of hygienic and environmentally harmful lead oxide. During the melting process do not volatilize environmentally irregular lead oxides and arsenic that are used in the manufacture of lead crystal glasses. As it is completely lead-free and is designated above all for the utility glass and consequently for beverage glass and household use it involves the significant advantage that no undesired and healthy damaging lead oxide will pass over into the leaching. Examples of carrying out invention This invention will be explained in more detail in the following examples of carrying out. E x a m p l e N o. 1 2 3 4 Glass components content in % by weight Silicium dioxide Si0 2 63,883 64,857 63,170 64,363 Aluminium oxide A1 2 0 3 0,108 0,117 1,800 0,117 Zirconium dioxide Zr0 2 7,522 6,111 5,820 5,081 Hafnium dioxide Hf0 2 0,233 0,189 0,180 2,219 Titanium dioxide Ti0 2 0,012 0,010 0,009 0,011 Calcium oxide CaO 5,500 6,500 5,800 6,500 Magnesium oxide MgO 0,087 0,103 4,072 0,103 Zinc oxide ZnO 3,000 5,500 2,500 3,000 Potassium oxide K 2 0 6,000 4,000 4,000 4,000 Sodium oxide Na 2 0 13,000 12,000 12,000 12,000 Antimony trioxide Sb 2 0 3 0,500 0,500 0,500 0,500 Iron content expressed by content of iron trioxide Fe 2 0 3 0,015 0,015 0,018 0,015 Sulphates S0 4 2 ~ 0,004 0,003 0,003 0,004 Chlorides Cl " 0,086 0,029 0,078 0,043 Erbium oxide Er 2 0 3 0,040 - 0,042 0,044 Neodymium oxide Nd 2 0 3 0,010 - 0,008 - Cobaltous oxide CoO 0,00003 0,00005 0,00003 0,00004 Manganese oxides expressed by content of manganese oxide Mn0 2 0,066 Boron oxide B 2 0 3 2,000 Σ components 100,000 100,000 100,000 100,000 Refractive index at 589,3 nm 1,5469 1,5456 1,5454 1,545 ^lOgt^ [°C] 1202 1222 1219 1194 " • lo T A [°C] 1050 1068 1076 1050 t-logTFy.βδ [°C] 765 776 803 774 *-liquidus [°C] 930 960 960 915 hydrolitical resistance in ml [OO.Olmol.r 1 ] HCl 0,60 0,40 0,40 0,32 E x a m p l e N o. 5 6 7 8 Glass components content in % by weight Silicium dioxide Si0 2 70,739 61,632 64,015 71,497 Aluminium oxide A1 2 0 3 2,000 0,063 0,065 0,125 Zirconium dioxide Zr0 2 0,970 6,275 7,178 1,096 Hafnium dioxide Hf0 2 0,030 1 ,225 0,222 0,034 Titanium dioxide Ti0 2 0,027 1,000 0,011 0,027 Calcium oxide CaO 7,640 6,000 5,000 6,640 Magnesium oxide MgO 0,020 0,016 0,013 0,018 Zinc oxide ZnO 1,500 1,500 5,000 3,500 Potassium oxide K 2 0 3,400 5,800 4,500 3,600 Sodium oxide Na 2 0 12,570 13,000 12,000 12,570 Antimony trioxide Sb 2 0 3 0,600 0,500 0,500 0,600 Iron content expressed by content of iron trioxide Fe 2 0 3 0,008 0,008 0,010 0,008 Sulphates S0 4 2" 0,225 0,300 0,003 0,225 Chlorides Cl~ 0,043 0,131 0,040 0,038 Erbium oxide Er 2 0 3 0,020 0,050 0,085 0,022 Neodymium oxide Nd 2 0 3 0,008 - - - Ceric oxide Ce0 2 0,008 Cobaltous oxide CoO 0,000015 0,00005 - 0,00002 Nickel oxide NiO 0,0003 Boron oxide B 2 0 3 1,000 Lithium oxide Li 2 0 0,200 Stannic dioxide Sn0 2 0,500 — Bismuth oxide Bi 2 0 3 2,000 - Molybdic oxide Mo0 3 - 0,050 Tungstic oxide W0 3 - 0,300 Σ components 100,000 100,000 100,000 100,000 Refractive index at 589,3 nm 1,5204 1,5519 1,5408 1,5200 ^lo r-^ [°C] 1466 1423 1453 1473 * logn=3 [°C] 1194 1191 1209 1200 *- logn=4 [°C] 1027 1046 1057 1032 ^-logη=7,65 [°C] 717 770 769 721 ^ ■ logr l4,5 [°C] 484 555 547 487 liquidus [°C] 920 895 897 920 hydro li t ical resistance in ml [C= : 0, , oii nol.l "1 ] HCl 0,51 0,75 0,34 0,62 In examples carrying out corresponds t logη=2 to the melting temperature, t logη=4 to the working temperature, t logη _ 7>65 to the softening point temperature, t logη _ 13 to the upper annealing temperature and t logT , =U 5 to the lower annealing temperature. The values of hydrolitical resistance expressed in the consumption of 0,01 molar hydrochloric acid in mililitres show that all glasses mentioned fulfil the condition desired for classification in the third class of hydrolitical resistance. By rising the amount of zirconium dioxide Zr0 2 , hafnium dioxide Hf0 2 and zinc oxide ZnO in glasses mentioned the condition is given for the classification in the second class of hydrolitical resistance. The given composition of lead-free glass types according to this invention can be also applied into basic composition of coloured glass types that are coloured by using usual procedures and known types of colouring substances and their combinations in current concentrations as well. Industrial applicability The lead-free crystal glass with the refractive index higher than 1,52 according to this invention is assigned to the production of man-made and machine-made utility glass, for the products of luxurious character in plain but especially decorated designs using engraving, cutting and further decorative techniques. This type of glass is suitable for processing by diamond, carborundum, electrite, ate. tools, it is well polishable by chemical and mechanical treatment and features a high light transmittance and perfect clearness. It can be applied as initial basis for coloured glass types. This glass is hygienic unharmful concerning the content of detrimental substances in the leaching and by its brilliance can compete with the products made of lead crystal glass. In question is the production of glass objects used in households and restaurants, e.g. small cups, tumblers, carafes, bowls and, vessels of various shapes and sizes used for decorative purposes such as vases, dishes, etc., including applied art designs and objects of art.

Claims: Cl a ims 1. Lead-free crystal glass with the refractive index higher than 1,52 suitable especially for production of man-made and machine-made utility glass containing silicon dioxide Si0 2 , aluminium oxide A1 2 0 3 , zirconium dioxide Zr0 2 , hafnium dioxide Hf0 2 , titanium dioxide Ti0 2 , calcium oxide CaO, magnesium oxide MgO, zinc oxide ZnO, potassium oxide K 2 0, sodium oxide Na 2 0, antimony trioxide Sb 2 0 3 , iron trioxide Fe 2 0 3 , sulphates , chlorides and at least one component from the group including erbium oxide Er 2 0 3 , neodymium oxide Nd 2 0 3 , eerie oxide Ce0 2 , cobaltous oxide CoO, nickel oxide NiO, manganese oxides and selenium compounds, characterized by its composition, with the content 50 to 75 % by weight of silicon dioxide Si0 2 , 0,05 to 10 % by weight of aluminium oxide A1 2 0 3 , 0,05 to 15 % by weight of zirconium dioxide Zr0 2 , 0,001 to 2,5 % by weight of hafnium dioxide Hf0 2 , 0,001 to 5 % by weight of titanium dioxide Ti0 2 , 2 to 9 % by weight of calcium oxide CaO, 0,001 to 6 % by weight of magnesium oxide MgO, 0,05 to 10 % by weight of zinc oxide ZnO, 0,1 tύ 10 % by weight of potassium oxide K 2 0, 5 to 16 % by weight of sodium oxide Na 2 0, 0,05 to 2,5 % by weight of antimony trioxide Sb 2 0 3 , the total amount of iron expressed as iron trioxide Fe 2 0 3 being ranged from 0,005 to 0,035 % by weight, while this glass further contains 0,0001 to 1,25 % by weight of sulphates S0 4 2" and chlorides Cl~ and 0,000005 to 0,8105 % by weight of at least one component from the group comprising erbium oxide Er 2 0 3 , neodymium oxide Nd 2 0 3 , eerie oxide Ce0 2 , cobaltous oxide CoO, nickel oxide NiO, manganese oxides and selenium compounds, the total of all components mentioned being at least 99,6 % by weight. 2. Crystal lead-free glass with the refractive index higher than 1,52 according to claim 1, characterized by its composition, with the content of 0,0001 to 0,75 % by weight of sulphates S0 4 2" and 0,001 to 0,5 % by weight of chlorides Cl " . 3. Crystal lead-free glass with the refractive index higher than 1,52 according to claims 1 and 2, characterized by its composition, with the content at least of one component from the group comprising 0,0001 to 0,2 % by weight of erbium oxide Er 2 0 3 , 0,0001 to 0,2 % by weight of neodymium oxide Nd 2 0 3 , 0,001 to 0,2 % by weight of eerie oxide Ce0 2 , 0,000005 to 0,0005 % by weight of cobaltous oxide CoO, 0,00001 to 0,005 % by weight of nickel oxide NiO, 0,001 to 0,200 % by weight of manganese oxide Mn0 2 expressing in re-count manganese oxides and 0,00001 to 0,005 % by weight of selenium expressing in re-count selenium compounds. 4. Crystal lead-free glass with the refractive index higher than 1,52 according to claims 1 to 3, characterized by its composition, with the content at least of one oxide from the group comprising 0,05 to 6 % by weight of barium oxide BaO, 0,001 to 5 % by weight of boron oxide B 2 0 3 , 0,001 to 1,5 % by weight of phosphoric oxide P 2 0 5 and 0,001 to 1,5 % by weight of lithium oxide Li 2 0. 5. Crystal lead-free glass with the refractive index higher than 1,52 according to claims 1 to 3 or according to claims 1 to 4, characterized by its composition, with the content at least one component from the group comprising 0,05 to 5 % by weight of stannic dioxide Sn0 2 , 0,05 to 2 % by weight of lanthanum oxide La 2 0 3 , 0,05 to 10 % by weight of bismuth oxide Bi 2 0 3 , 0,001 to 0,1 % by weight of molybdic oxide Mo0 3 and 0,001 to 0,5 % by weight of tungstic oxide W0 3 .

Inventors: RADA MIROSLAV, SASEK LADISLAV, RADA, MIROSLAV, SASEK, LADISLAV
Applicants: RADA MIROSLAV, SASEK LADISLAV, VYSOKA SKOLA CHEM TECH, RADA, MIROSLAV, SASEK, LADISLAV, VYSOKA SKOLA CHEMICKO - TECHNOLOGICKA
Application year: 1993
Main classification: C03C3
IPC codes: C03C3, C03C4