Compositions – Light transmission modifying compositions – Modification caused by energy other than light
Patent
1981-12-14
1984-12-25
Kyle, Deborah L.
Compositions
Light transmission modifying compositions
Modification caused by energy other than light
2523014F, 252584, 252586, C30B 2934
Patent
active
044902867
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to optoelectronics, and more specifically to sodalite group materials exhibiting either photochromic or cathodochromic properties, or both, and employed for manufacture of sensing elements used in video recording or radiation field registration, and photoelectric or visual readout of the information stored, using coherent and incoherent light. The invention also concerns methods of preparation of photochromic and/or cathodochromic sodalite materials. It is another object of the invention to offer sensing elements made of such materials and used in variable light transmission devices including those providing for cathode-ray information storage and display, optically controlled spatial/temporal light flux modulation, registration of ionizing radiation fields such as ultraviolet and X-ray radiations, and the nuclear particle flux.
BACKGROUND OF THE INVENTION
Sodalites fall into the category of cage type aluminosilicates in which aluminum and silicon ions are tetrahedrally surrounded by oxygen ions to form a three-dimensional aluminosilicate cage structure with cubic octahedral cavities. Part of these cavities, or all of them, are filled with halogen ions tetrahedrally surrounded by alkali metal ions. The degree of filling the sodalite cage cavities is indicative of the amount of nonstoichiometry of the sodalite structure which is the main governing factor controlling the photochromic and cathodochromic properties of sodalites. In this case, the 100%-filling of the sodalite cage cavities with alkali-halide tetrahedra is equivalent to stoichiometric form, and correspondingly, to zero amount of nonsoichiometry. The crystal lattice of the sodalite cage structure has cubic symmetry, and hence the sodalite crystals are optically isotropic.
The crystalline structure of sodalite in the form of mineral chlorosodalite was first thoroughly investigated and described by L. Pauling in 1930 (L. Pauling, "The structure of Sodalite and Helvite", Zeitschrift fur Kristallografie, v.74, 1930, p.213). In the natural chlorosodalite studied by L. Pauling, which has an idealized chemical formula Na.sub.6 Al.sub.6 Si.sub.6 O.sub.24.2(NaCl), between 85 and 90% of cavities of the aluminosilicate cage are filled with ClNa.sub.4 -tetrahedra. The lattice constant of the aluminosilicate cage of this sodalite is 8.87 .ANG., and, correspondingly, the volume of each cubic octahedral cavity is about 150 .ANG..sup.3.
On discovering photochromic, and subsequently, cathodochromic properties in natural chlorosodalites, some attempts were made to use these materials for manufacturing the screens of cathodochromic CR storage tubes known as the sciatrons. The industrial application of natural sodalites in optoelectronics, however, was limited by the shortage of raw materials, high cost of extraction and processing, high proportion of impurities, low nonstoichiometry value of the composition, and other causes. Consequently, the development of synthetic sodalite materials was initiated resulting in a wide range of sodalites of different chemical compositions.
The known synthetic sodalite materials widely vary in their chemical composition. So, for example, sodalite materials have been synthesized in which part of the Al.sup.3+ and Si.sup.4+ ions of the aluminosilicate cage is repplaced by Ga.sup.3+ and Ge.sup.4+ ions, respectively. Known are synthetic sodalite materials which, unlike the previously described chlorosodalite, contain ions of halogens other than chlorine (Cl.sup.-), namely: fluorine F.sup.-, bromine Br.sup.-, and iodine I.sup.-, separately or in combination, and part of the sodium ions (Na.sup.+) is replaced by ions of other alkali or alkaline-earth metals. Some synthetic sodalite materials may contain alloying additions such as SO.sub.4.sup.2, S.sup.2-, Se.sup.2-, Te.sup.2-, WO.sub.4.sup.2-, etc. The desired photochromic and cathodochromic properties of sodalite materials are provided by varying the chemical composition. Here the crystalline structure of sodalites remains unaltered, but
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patent: 3799881 (1974-03-01), Shidlovsky
patent: 3923529 (1975-12-01), Araujo et al.
patent: 3959584 (1976-05-01), Todd, Jr.
Pauling, "The structure of Sosalite and Helvite", Zeitschrift fur Kristallografie, V. 74, 1930, p. 213.
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Demidenko Vladimir A.
Denisov Roman A.
Denx Viktor P.
Dydelzak Alexandr E.
Ryzhikov Engels N.
Brookes Anne
Institut Fiziki Akademii Nauk Estonskoi SSR
Kyle Deborah L.
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