Abstract: Single mode and multimode silica-based optical fibers having a down-doped outer cladding are disclosed. The outer cladding material is derived from a preexisting silica tube that comprises an amount of index-lowering dopant, typically F or B, sufficient to result in an effective refractive index of the material that is at least about 0.001, preferably at least 0.0025, lower than the refractive index of SiO.sub.2. Single mode optical fiber according to the invention typically requires a smaller amount of deposited cladding material than an equivalent prior art fiber, and thus can be produced more economically. Multimode optical fiber according to the invention may have lower core doping or higher NA than equivalent prior art fiber. Down-doped substrate or sleeve tubes advantageously are produced by a gel process.

Abstract: High silica glass is formed by sintering a dried gel. The gel has a pore size distribution such that at most about 5% of the total pore volume is contributed by pores having an effective pore diameter greater than about 0.5 .mu.m, and such that at least 10% of the total pore volume is contributed by pores having an effective pore diameter greater than about 0.02 .mu.m. This pore size distribution permits effective migration of fluid into, and out of, the gel, permits sintering at a lower temperature, and results in increased perfection of the glass. The pore size distribution can be achieved by appropriate comminution, e.g., ball-milling, of intermediate material. A novel process for forming high silica glass is also disclosed. The process comprises forming intermediate material by hydrolysis of one or more metal alkoxides, comminuting the intermediate material to produce colloidal particles, forming a sol by dispersing the particles in liquid, gelling the sol, drying the gel, and sintering the dried gel.

Abstract: Inexpensive Mn or Mg ferrites may be used as negative temperature coefficient thermistors. Fabrication of devices with the desired high temperature coefficients is facilitated by a processing method which forms a thin layer of oxidized and high resistivity material on a low resistivity layer of ferrite material.

Abstract: High-silica glasses are formed by sintering a dried gel at temperatures below the liquidus. The gel may be formed by mixing colloidal silica particles or silica-containing liquids with appropriate liquids. Fragmentation of the gel during drying is advantageously avoided by redispersing the dried gel or sol in a liquid to yield a colloidal suspension which is then gelled, dried, and finally sintered below the liquidus.

Abstract: Preparation of ceramic materials, including ferrites and garnets, through a processing sequence that includes a sintering step is facilitated by a flux, having a relatively low melting temperature and an approximately eutectic composition consisting of two or more of the final ceramic components. The flux permits the sintering step to proceed at temperatures lower than otherwise possible, and results in better control of the final ceramic composition and microstructure.

Abstract: Many ceramics are produced with a processing sequence that includes spray drying or ball milling a slurry. To produce ceramics with the best properties and to facilitate ball milling or spray drying, a dispersant is normally added to the ceramic slurry. Ammonium citrate and polyethylenimine have been found to produce ceramic slurries with the desired characteristics. The dispersants appear especially well suited for use with ferrite slurries.

Abstract: Display devices are described which contain, in addition to organic quinones and suitable organic solvent, a solid ionic conductor. Such display devices are advantageous because of exceptional persistence of the display. Thus, an image may be retained without application of electrical energy. In addition, these displays exhibit high optical contrast and low power consumption. Under certain conditions, these devices are non-linear (exhibit sharp thresholds) which permit multiplexing. This is highly advantageous in display device applications.

Abstract: Many ceramics are produced with a processing sequence that includes spray drying or ball milling a slurry. To produce ceramics with the best properties and to facilitate ball milling or spray drying, a dispersant is normally added to the ceramic slurry. Ammonium citrate and polyethylenimine have been found to produce ceramic slurries with the desired characteristics. The dispersants appear especially well suited for use with ferrite slurries.

Abstract: Desirable properties of manganese zinc ferrites are obtained without the need for controlling or changing the oxygen partial pressure during the sintering and cooling steps by adding a small amount of germanium or gallium to the ferrite and using an atmosphere, such as air, during the sintering and cooling steps, that has at least 1 percent oxygen by volume.