Creep in pore-free polycrystalline aluminum oxide has been studied as a function of temperature, grain size, and strain rate. The behavior may be described byσαd2ε̇, where d is the mean grain diameter. Deformation is not controlled by basal slip but by a diffusional creep process as described by Nabarro and Herring, [F. R. N. Nabarro, Conference on Strength of Solids (The Physical Society, London, 1948), p. 75; C. Herring, J. Appl. Phys. 21, 437 (1950)].
A highly efficient room-temperature nanolaser Phys. Today 60, 24 (2007); 10.1063/1.2774088 Fast, high-efficiency, and homogeneous room-temperature cathodoluminescence of ZnO scintillator thin films on sapphire Measurements and calculations of CO2 roomtemperature highpressure spectra in the 4.3 μm region Pulsed room-temperature laser action at 2.06 p.m has been achieved using Ho3+: YLF ILiF 4) sensitized with Er3+ and Tms+. An unoptimized cavity gave a threshold of 35 J and a slope efficiency of 1. 3% in normal mode with an output mirror of 62% T. A slope efficiency of 2% and a 65-J threshold were observed in Q-switched operation along with Q-switched energy of> 500 mJ from a 0.9 x i-in. rod. The sensitizer ions have broad absorption bands and transfer times (to the active ion) of 150-200 p.sec.
The Stark levels of the 4I15/2 ground state manifold have been determined for Er3+-doped fluorozirconate, fluorophosphate, phosphate, and silicate bulk glasses from fluorescence-line-narrowing (FLN) measurements at 4.2 K. Splittings between adjacent Stark levels were observed to be 10–140 cm−1 and the total energy spread of the manifold was found to range from 335 to 400 cm−1. The position of a given Stark level varies up to 60 cm−1 depending on the particular Er3+ sites excited. Using the 4.2-K results, homogeneous broadening is found to be a reasonable approximation for the 300-K luminescence band of the glasses examined. Results are also presented for silica preforms as well as for a barium-zinc-lutetium-thorium fluoride composition. The FLN studies together with a Judd–Ofelt [Phys. Rev. 127, 750 (1962); J. Chem. Phys. 37, 511 (1962)] analysis of the absorption data suggest similarities in the local environment between the fluorozirconates and the high-fluorine fluorophosphates.
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