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Red colored bright visible light fracto-mechanoluminescence was observed successfully from ruby (Cr doped Al2O3) and Cr doped spinel (Cr doped MgAl2O4) crystals in mechanical processes such as cutting, grinding and polishing. Fracto-mechanoluminescence spectra from ruby (peaking at λ=696 nm) and Cr doped spinel (peaking at λ=693 nm) perfectly agree with those of photoluminescence (PL) from Cr3+ ions in ruby and spinel crystals, respectively. In the grinding and polishing processes, peak intensities and peak wavelength of fract-mechanoluminescence from ruby and Cr doped spinel crystals varies with roughness (grain size, #) of the diamond disk. Fracto-mechanoluminescence is expected to be used in the in-situ evaluation of fracture of crystals in cutting, grinding and polishing for highly precise mechanical processes. [ABSTRACT FROM AUTHOR]

Photoluminescence and visible light thermal radiation from Eu, Al doped SiO2 (SiO2:Eu, Al) glass fiber have been studied for a fiber-optic thermometer application. Photoluminescence (PL) peaking at λ=433, 485 and 617 nm is clearly observed from SiO2:Eu, Al glass with UV excitation (λ=365 nm). Peak intensity of PL decreases with temperature form 300 to 1000 K. Visible light thermal radiation peaking at λ=660 nm is also observed from SiO2:Eu, Al glass above 1000 K. Peak intensity of visible light thermal radiation increases exponentially with temperature. Temperature can be measured based on temperature dependences of PL (below 1100 K) and visible light thermal radiation (above 1000 K) using SiO2:Eu, Al glass fiber. The hybridization of fluorescence thermometry (below 1000 K) and thermal radiation thermometry (fiber-optic pyrometer, above 1000 K) using SiO2:Eu, Al glass fiber is thought to extend the temperature range of a fiber-optic thermometer. [ABSTRACT FROM AUTHOR]

Visible light thermal radiation from SiO2 glass doped with Y, La, Ce, Pr, Nd, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu were studied for the fiber-optic thermometer application based on the temperature dependence of thermal radiation. Thermal radiations according to Planck's law of radiation are observed from the SiO2 fibers doped with Y, La, Ce, Pr, Eu, Tb, and Lu at the temperature above 1100 K. Thermal radiations due to f-f transitions of rare-earth ions are observed from the SiO2 fibers doped with Nd, Dy, Ho, Er, Tm, and Yb at the temperature above 900 K. Peak intensities of thermal radiations from rare-earth doped SiO2 fibers increase sensitively with temperature. Thermal activation energies of thermal radiations by f-f transitions seen in Nd, Dy, Ho, Er, Tm, and Yb doped SiO2 fibers are smaller than those from SiO2 fibers doped with Y, La, Ce, Pr, Eu, Tb, and Lu. Thermal radiation due to highly efficient f-f transitions in Nd, Dy, Ho, Er, Tm, and Yb ions emits more easily than usual thermal radiation process. Thermal radiations from rare-earth doped SiO2 are potentially applicable for the fiber-optic thermometry above 900 K. [ABSTRACT FROM AUTHOR]

Fiber-optic thermometry based on temperature dependence of thermal radiation from Tm3+ ions was studied using Tm end doped SiO2 fiber sensor. Visible light radiation peaks due to f-f transition of Tm3+ ion were clearly observed at λ = 690 and 790 nm from Tm end doped SiO2 fibers sensor at the temperature above 600 °C. Thermal radiation peaks are assigned with f-f transition of Tm3+ ion, ¹D2- ³H6, and ¹G4-³H6. Peak intensity of thermal radiation from Tm3+ ion increases with temperature. Intensity ratio of thermal radiation peaks at λ = 690 nm against that at λ = 790 nm, I790/690, is suitable for the temperature measurement above 750 °C. Two-dimensional temperature distribution in a flame is successfully evaluated by Tm end doped SiO2 fiber sensor. [ABSTRACT FROM AUTHOR]