Characterization and identification of local defects in glass.

The most relevant defects in glasses are categorized and investigated by appropriate microanalytical techniques. Since these defects very often present a real challenge because of complex chemical and mineralogical properties, a multimethod approach is necessary to supplement or confirm the findings from scanning techniques. The combination of electron probe microanalysis/energy-dispersive x-ray (EPMA/EDX) and laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS) allows the determination of element trace concentrations in a knot, a glassy defect, thus finally enabling the identification of a special source of the defect from otherwise nondistinguishable refractories. The type of crystals can be determined exactly by the use of EPMA and x-ray dispersion (XRD), stones (a crystalline agglomerate) are analyzed by EPMA/EDX pointing to a possible source for this defect; results on metallic inclusions, "filled bubbles," and surface defects are reported and defect sources are discussed. Since close cooperation with the production departments and knowledge of production techniques and conditions are necessary for the diagnosis to take appropriate countermeasures, an approach is presented which systematically accumulates all information into a data base. The structure of such "expert systems" is described, which leads to correlation of appearance, analytical data, and source of the defects for even more accurate diagnosis and faster reaction.

Characterization of oxide coatings on glass.

Some representative characteristics of oxide films deposited on glass by different techniques have been briefly described as well as several relevant methods of thin-film analysis to determine these quantities. The most powerful information obtained by some analytical techniques have been given, and some typical problems that may occur during the analysis of oxidic thin films have been discussed. With a few selected results, the potential of some modern methods has been demonstrated.

Comparative photothermal study of reactive low-voltage ion-plated andelectron-beam-evaporated TiO(2) thin films.

The thickness-dependent optical and thermal properties and the corresponding damage thresholds have been investigated by means of various photothermal techniques on titanium dioxide thin films prepared by the conventional techniques of reactive electron-beam evaporation and reactive low-voltage ion plating (RLVIP). Compared with the reactive-electron-beam-evaporated samples, the RLVIP films exhibit a higher absorption, lower damage threshold, better thermal conductivity, lower defect density, and an almost perfect stability under Ar(+)-laser irradiation. These results are correlated with data from a multimethod approach, and a mechanism is proposed to explain the low damage threshold for the RLVIP TiO(2) films.