Luminescent glass heating

Marcantoncetos et al. [112] have described a phosphorimetric method for the determination of traces of boron in seawater. This method is based on the observation that in the glass formed by ethyl ether containing 8% of sulfuric acid at 77 K, boric acid gives luminescent complexes with dibenzoylmethane. A 0.5 ml sample is diluted with 10 ml 96% sulfuric acid, and to 0.05-0.3 ml of this solution 0.1ml 0.04 M dibenzoylmethane in 96% sulfuric acid is added. The solution is diluted to 0.4 ml with 96% sulfuric acid, heated at 70 °C for 1 h, cooled, ethyl ether added in small portions to give a total volume of 5 ml, and the emission measured at 77 K at 508 nm, with excitation at 402 nm. At the level of 22 ng boron per ml, hundredfold excesses of 33 ionic species give errors of less than 10%. However, tungsten and molybdenum both interfere. 

Other Aluminosilicates, Transparent mullite glass-ceramics can be produced from modified binary Al C —Si02 glasses (21). In these materials, the bulk glass phase separates into tiny alumina-rich droplets in a siliceous matrix. Further heat treatment causes these droplets to crystallize to mullite spherulites less than 0.1 Jim in size. When doped with ions such as Cr3+, transparent mullite glass-ceramics can be made to absorb broadly in the visible while fluorescing in the near-ii (22,23), thereby making them potentially useful for luminescent solar collectors. 

Fig. 4.19, The tunnelling luminescence kinetics for the Ej-, Tb3+ pairs in Na20 3Si02-Tb3+ glass. The ultraviolet excitation was at 120 K with further short thermal excitation of electrons above the mobility edge (curve 1) and prolonged heating up to 70 K below the excitation...

One instance of visual observation of a luminescence has been reported by Gallagher (164). He noted a glow from an irradiated sample of benz-aldehyde phenylhydrazone when heated to 100°C. on a watch glass. Unfortunately, Zanella (166) was unable to reproduce this experiment. 

CuInSe2XTe2(i-x) nanoparticles incorporated into silicate glass reveal complicated photoluminescence with the above-than-band gap excitation. It depends on composition of nanoparticles. The secondary heat treatment differently affects the selenides and tellurides. Defect states within the particles and excitons are proposed as possible sources of the luminescence. 

It must be noted at this point that transparent PbTiO glass-ceramics are of interest for electro-optic and electro-luminescent applications (Kokubo and Tashiro, 1976). Non-transparent, opaque PbTi03 glass-ceramics, however, can be used for thick-film capacitors with a dielectric constant of 94 and tan 6 of 0.0130 (at 10 c/s) on alumina substrates that have been heated to temperatures up to approximately 600°C. The dielectric constant of the capacitor as a function of temperature is almost linear from room temperature to 270 C, with a temperature coefficient of 0.00083 K Therefore, it was found that glass powders were suitable for preparing capacitors with a high dielectric constant (Kokubo and Tashiro, 1976). 

The absorption and PL spectra of TA-PPP do not overlap, indicative of a good luminescent material. The PL quantum efficiency, though not quantitatively measured, is comparable to that of pristine DO-PF, which is in the range of 70-100%. A thin film of TA-PPP cast on glass was heated on a hot plate at 100 °C in laboratory air and normal room light for 1 month. No PL degradation... 

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