Abstract: The preparation of an amorphous gel of a hydrated oxide is coupled with the technique of controlled seeding to obtain monosize crystallized particles. Crystalline oxide particles, such as phosphors, are formed by a method comprising: (a) selecting an oxide system; (b) forming an amorphous phase of the oxide system; (c) controllably forming nuclei in the amorphous phase; and (d) converting the amorphous phase to the crystalline oxide particles by growth of the nuclei. The oxide particles have a substantially single size, with a narrow size distribution.

Abstract: A precursor material is superoxidized to a superconducting oxide material in an atmosphere containing a reactive component that reacts with and removes hydroxide ion (OH.sup.-), replacing it with peroxide ion (O.sup.-). Preferred reactive components include H.sub.2 O.sub.2, N.sub.2 O, and I.sub.2. The reactive component reacts with and removes hydroxide ion from the precursor material, to reach a higher oxidation state in the superconducting oxide material than possible by oxidation in molecular oxygen. The use of such a reactive component permits both faster oxidation of the precursor material at conventional temperatures and the use of lower temperatures to achieve oxidation.

Abstract: A process is provided for fabricating coated particles of a substantially uniform particle size. The process comprises coating small particles of well-defined crystalline phases with a polymerized gel. The process results in a ball-type sol-gel coating of the particles to provide particles which have a narrow size distribution. In many instances, crystalline particles of irregular shape have a substantially spherical shape upon coating with the sol-gel. In instances where the core is a high melting point material, such as an oxide, nitride, or carbide, the coat formulation can effect a low sintering temperature, which permits forming films of the particles at a much lower temperature than would otherwise be possible.

Abstract: High temperature superconducting oxide materials can be taken to a higher, but stable, state of oxidation by removing H-impurities, such as OH.sup.-, using I.sub.2 /O.sub.2 mixtures in a reactive atmosphere process. A higher T.sub.c and a narrower .DELTA.T-transition result.

Abstract: A ceramic sensor (12) comprising a thin film (14) of Cu.sub.1=x Mn.sub.2-x O.sub.4-y is provided that quantitatively measures the partial pressure of CO gas in a flowing system (22). The sensor is specific to CO gas and is negligibly affected by the presence of the common automobile exhaust vapors NO, H.sub.2 O, and CH.sub.4, within the operational temperature range from about 250.degree. to 450.degree. C. The CO sensor of the invention has other applications, such as monitoring CO levels in laboratories, mines, and industrial smoke stacks, and may be used in environments up to about 700.degree. C.

Abstract: A novel, solid-state, low-temperature preparation of barium sulfate provides a higher purity material than that obtained by the conventional method of precipitation. The reaction involves heating a barium oxysalt in the presence of at least one sulfur-containing species for a period of time.

Abstract: A high concentration of diatomic molecules is caged in a host crystal by a crystal growth process, in which all other internal degrees of freedom of the diatomic molecule, except the vibrational, are frozen. Such a system provides an efficient mid-infrared, solid-state laser that can be pumped by a laser diode. Other uses include magnetic (Faraday) rotators, electro-optic switches, and Q-switches. The crystal growth process employs Czochralski-type or Bridgman-type processes under high pressure to introduce the diatomic molecule into the host lattice at a temperature slightly above the melting point of the host crystal, followed by slow cooling.

Abstract: Post-growth gas-impregnation of an ionic crystal is provided to achieve a high level of caged neutral diatomic species or charged diatomic species, where all other internal degrees of freedom of the species, except the vibrational, are frozen. In the former case, the neutral diatomic species (molecules) enter interstitially, while in the latter case, the charged diatomic species (anions) substitute for anions on the crystal lattice. Such a system provides an efficient mid-infrared, solid-state laser that can be pumped by a laser diode. Other uses include magnetic (Faraday) rotators, electro-optic switches, and Q-switches. The impregnation process introduces the species into the host lattice at a temperature below the melting point of the host crystal, and preferably at a phase transition of the crystal, followed by slow cooling.

Abstract: A fluoride glass is prepared by depositing a solid including a metal fluoride on a heated substrate, from a gaseous mixture of a nonmetallo-organic compound, carbon dioxide, and a source of carbonyl fluoride. The nonmetallo-organic compound contains the metallic cation of the metal fluoride bonded to an organic species through an electronegative element such as oxygen, but not directly to a carbon atom. The carbon dioxide, or optionally another species reactive with carbon to produce a gas, oxidizes solid carbon and other reduction products of the organic compound that could otherwise be present in the deposited metal fluoride to impair optical properties of the fluoride glass. The carbonyl fluoride, supplied by the gas itself or by reactants that produce the gas, reacts with the nonmetallo-organic compound without producing water, which would otherwise degrade the glass purity.

Abstract: Metal sulfides are prepared by reacting a compound of the metal and an oxygen-containing anion, with a source of carbonyl sulfide. The resulting metal sulfide is not contaminated by hydrogen, as in the form of hydroxides, and is suitable for use in photoluminescence and electroluminescence applications. The starting material is preferably a metal oxalate, which may be appropriately doped, and the source of the carbonyl sulfide is preferably a mixture of carbon monoxide and sulfur dioxide (to produce a reducing mode) or a mixture of carbon dioxide and carbon disulfide (to produce an oxidizing mode). Oxyanions that decompose to a produce a nascent oxygen anion, as does the oxalate, are preferred, as they can be reacted to achieve a high conversion rate to the sulfide.

Abstract: A preform for preparation of optical fibers is prepared by inserting a rod of a higher index of refraction fluoride glass into the bore of a hollow cylinder of a lower index of refraction fluoride glass fiber. This preform precursor is processed to collapse the hollow cylinder inwardly to form a composite preform having a high-refractive index core and a low-refractive index casing. The preparing of the glasses and processing to a preform are accomplished in a reactive environment that reacts and removes oxygen and hydrogen containing species from the glass, the reactive environment being, for example, Cl.sub.2, CCl.sub.4, SF.sub.6, BF.sub.3, CF.sub.4, or the decomposition products of a liquefied solid fluorocarbon. The preform is then drawn to an optical fiber.

Abstract: A method for preparing compounds of sulfur, selenium, and tellurium includes the formation of the compound from the elements in a closed environment which excludes oxygen, and then the purification of the compound by contacting it with carbon or carbon monoxide. Oxygen, the principal contaminant in conventionally prepared compounds of this group, is excluded from the formation of the compound in the formation step by using a closed reactor, preferably made of vitreous silica. Oxygen in the initial elemental reactants remains in the compound made in this way, and the purification step eliminates the oxygen originally present in the elemental reactants from the compound. Arsenic triselenide made by this approach, glassy and of high purity, is suitable for use in applications requiring infrared transparency.

Abstract: This invention provides a method for the preparation of ultrapure active metal fluorides of increased purity from their metal oxides by reacting an active metal with a predetermined amount of HF(aq) to form a solid reaction product which is dried under controlled heating to form a hydrated fluoride. This hydrated active metal fluoride is then subjected to reactive atmosphere processing comprising hydrofluoric acid vapor in a CO.sub.2 reactive carrier gas and a selected halide compound in the gas phase for a predetermined period of time to further increase anion purity.

Abstract: A catalyst material having a catalyst metal supported on a substrate, wherein the substrate has at least two types of surface atomic sites at which the catalyst metal can reside, and the catalyst metal resides primarily in one of those types of sites. In one catalyst material having platinum supported on an aluminum oxide substrate, the platinum atoms are located predominantly in the substrate sites having the lowest activation energy for catalysis of a chemical reaction. Population of only the low energy type of site is achieved by limiting the platinum content to from about 0.25 to about 1.0 atomic percent.

Abstract: A process of fabricating a hybrid single crystal fiber having nonlinear optical properties such as frequency doubling. Said process includes applying a force to a fiber core resting upon a bulk nonlinear crystal such as LiIO.sub.3 in a saturated solution of LiIO.sub.3 in water. After the core is embedded a sufficient distance into the crystal the force is removed.

Abstract: (Nb.sub.1-x Ta.sub.x).sub.2 O.sub.5 ("NTO") is purified of undesirable impurity elements present in small amounts by contacting the NTO in finely divided form to an extraction phase containing chloride, bromide, or iodide ions at a temperature whereat the ions react to remove the impurities into the extraction phase, and then the extraction phase is separated from the finely divided NTO. The process is particularly valuable in removing 3d impurities such as iron and titanium. The process can be carried out by liquid phase extraction, as with an azeotropic aqueous hydrochloric acid extraction from the NTO, or by gas phase reaction, as by reacting carbon tetrachloride with the NTO.

Abstract: This invention provides a method for the preparation of ultrapure active metal fluorides of increased purity from their metal oxides by reacting an active metal with a predetermined amount of HF(aq) to form a solid reaction product which is dried under controlled heating to form a hydrated fluoride. This hydrated active metal fluoride is then subjected to reactive atmosphere processing comprising hydrofluoric acid vapor in a CO.sub.2 reactive carrier gas and a selected fluoride compound in the gas phase for a predetermined period of time to further increase anion purity.

Abstract: A method is disclosed for the growth of single crystals of a binary metal oxides of the formula ABO.sub.3 where A is an alkali or alkaline earth metal, B is at least one element selected from titanium, niobium and tantalum. A mixture comprising the constituent components of the ABO.sub.3 crystal is prepared using a basic oxide or carbonate of A and a stoichiometric excess of an acidic oxide of B. The mixture is heated at an elevated temperature to form a melt and is thereafter exposed to a reactive atmosphere of a mixture of gaseous carbon monoxide and carbon dioxide. Crystal growth from the melt is effected by a top-seeded crystal pulling technique.

Abstract: The present invention relates to a method of producing a fluoride glass preform and/or fiber having a modified refractive index by heating the fluoride glass preform to a temperature that is above its glass transition temperature, but below its devitrification temperature; inserting a first electrode into the inner core of the preform and surrounding the outer perimeter of the preform with a second electrode of opposite polarity; means for generating an electromotive force; and applying an electromotive force through the first electrode and the second electrode which causes a movement of positive ions toward the electrode of opposite charge while simultaneously causing a movement of negative ions toward its electrode of opposite charge such that the movement of these ions results in a modification of the refractive index of the preform.

Abstract: The present invention relates to a low temperature method of preparing a compound of the formula:ABO.sub.3whereinA=Ba, Sr, Ca and Pb; andB=Ti, Zr and Hf,by(a) reacting a B-alkoxide, with a predetermined amount of aqueous A-hydroxide,(b) heating the reaction mixture to an initial temperature of 100.degree. C.-250.degree. C. at 1-40 atmospheres of pressure;(c) cooling the reaction mixture and thereafter, heating it to a subsequent temperature of approximately 40.degree. C. to 60.degree. C.;(d) dialyzing the cooled reaction product and recovering the tenate.