Sapphire Fig

The crystal structures of transition metal compounds and minerals have either cubic or lower symmetries. The cations may occur in regular octahedral (or tetrahedral) sites or be present in distorted coordination polyhedra in the crystal structures. When cations are located in low-symmetry coordination environments in non-cubic minerals, different absorption spectrum profiles may result when linearly polarized light is transmitted through single crystals of the anisotropic phases. Such polarization dependence of absorption bands is illustrated by the spectra ofFe2+ in gillespite (fig. 3.3) and of Fe3+in yellow sapphire (fig. 3.16). 

Representative optical spectra of various sapphires are illustrated in fig. 4.16. It is apparent from the spectra of the natural blue sapphire (fig. 4.16b) that absorption minima in the violet-indigo and blue-green regions, which are located between sharp peaks at 25,680 cm-1 and 22,220 cm-1 and broad bands spanning 17,800 to 14,200 cm-1, are responsible for the blue coloration. Absorption at 17,800 to 14,200 cm-1 is less intense in spectra of natural yellow sapphire (fig. 4.16a see also fig. 3.21) containing negligible Ti. The spectra of synthetic Ti3+-doped A1203 (fig. 4.16c) show absorption maxima at... 

Fig. 1. The Verneuil technique, or flame-fusion growth, as used for synthetic mby and sapphire.

The PVFj gauge has been calibrated up to 4 GPa (Bauer, 1984) for both shock loading and release. Graham and Lee (1986) have extended these calibration studies to about 20 GPa, and have measured both a shock loading and release profile in sapphire at 12 GPa, as indicated in Fig. 3.15. 

Fig. 2.9. The measured stress-volume relation of shock-loaded sapphire reveals a substantial reduction in strength, but a small finite strength is retained. The reduction in strength is indicated by the small high pressure offset between the static and shock data, and from extrapolation of high pressure shock data to atmospheric pressure conditions (Graham and Brooks [71G01]).

Experimental studies within the elastic range have been performed on monocrystalline AI2O3 (sapphire) and the nonpiezoelectric z-cut of quartz. Experiments are performed with a circuit devised by Ingram [68G05] in which a low-loss coaxial cable is used for both application of the potential and monitoring the current. As shown in Fig. 4.7, at an applied potential difference of a few kilovolts, a current of about 1 mA is produced at a compression of several percent. 

Fig. 4.7. The dielectric permittivity of impact-loaded dielectrics can be determined from current pulse measurements on disks biased with a voltage V. The magnitudes of the normalized current pulse values shown for two crystallographic orientations of sapphire are linear change with applied strain (after Graham and Ingram [68G05]).

Fig. 5.5. The electrical response of piezoelectric polymers under shock loading is studied experimentally by placing the thin PVDF element on the impact surface of a standard target, either the polymer, Kel F, z-cut quartz, or z-cut sapphire. The im-pactor is typically of the same material. The current pulse is recorded on transient digitizers with frequency responses from 250 to 1000 MHz.

Fig. 27. Abrupt contraction cell for flow visualization, birefringence and degradation measurements A inlet (from a peristaltic pump of a pressurized reservoir B outlet (atmospheric pressure or partial vacuum) C interchangeable metallic nozzle with a sapphire tip D capillary flow meter E glass window for flow visualization AP pressure drop (from pressure transducers)...

Fig. 2.16 Transmission vs. wavelength at 10 mm thick sapphire glass. Reprinted from Mishan et al. (2007) with permission...

As a contradistinction to the relatively simple case of AI2O3 Cr(III) where the color is due to a metal-centred electronic transition, we mention now on one hand the fact that the Cr(III) ion colors many transition-metal oxides brown (e.g. rutile Ti02 or the perovskite SrTi03 [15]), and on the other hand the fact that the color of blue sapphire (AI2O3 Fe, Ti [16]) is not simply due to a metal-centred transition. By way of illustration Fig. 1 shows the diffuse reflection spectrum of SrTiOj and SrTi03 Cr(III) [17], and Fig. 2 the absorption spectrum of Al203 Ti(III) and Al203 Ti(III), Fe(III) [18]. It has been shown that these colors are due to MMCT transitions and cannot simply be described by metal-centred transitions [19],... 

Consider first blue sapphire Al203 Ti(III), Fe(III) (Fig. 2). In the absence of Fe(III) the absorption spectrum is easy to interpret. The weak band with a maximum at about 500 nm is due to the t2 —> e crystal-field transition on Ti(III) (3d ), the strong band at 2<280nm is due to a Ti(III)-0( — II) LMCT transition. The absorption band in the region around 700 nm in the case of the codoped crystal cannot be due to Fe(III). It has been ascribed to MMCT, i.e. to a transition within an iron-titanium pair ... 

Fig. 4.6. (A) Schematic of femtosecond Ti Sapphire laser-pumped tunable continuum source (TCS) (B) fluorescence intensity image and (C) in situ...

Fig. 5.3. Top panel Polarization-dependent supercontinuum spectra obtained in sapphire. The corresponding variation in the diameter of the white light central spot as a function of incident polarization angle is shown in the lower panel...

Fig. 12.7 InGaAsP/InP multi quantum well semiconductor structure process (a) Si02 etch mask deposition (b) PMMA spin coating (c) E beam lithography and develop (d) Si02 etch (e) PMMA stripping (f) InGaAsP membrane etch (g) Si02 stripping (h) Chip flipping and bonding to sapphire (i) InP substrate etch (j) Adhesive etch...

We measured and analyzed the vertical emission from the resonators under pulsed optical pumping. The experimental setup is illustrated in Fig. 12.8a A Ti/sapphire mode-locked laser was used to optically pump the devices at a center wavelength of 980 nm, repetition rate of 76.6 MHz, and pulse duration of approximately 150 fs. A variable attenuator was used to control the pump power. The average pump power and center wavelength were monitored by a wavemeter, through a 50/50 beamsplitter. The pump beam is focused on the back side of the sample with a 50 x objective lens. A 20 x objective lens is used to collect the vertical emission from the sample and to focus it on an IR camera to obtain the NF intensity pattern and to... 

Fig. 3. Nano-second LIBS spectra of six sapphires. The dominant Be peak at 313.1 nm is marked.

The ball-value is a special type of vaporization cell (Fig. 8 i) which is used for the high pressure range from 10 to 760 torr. Depending on the temperature range, the material of the cell and of the ball may be Al, steel, gold or sapphire. The ball is situated on top of the cell so as to form a valve which opens when the inside pressure is higher than the outside pressure plus the weight of the ball. 

Fig. 7.18 (continued) (c) Light scattering apparatus used to detect polymer-polymer demixing 1 - HeNe laser, 2 - sapphire window, 3 - polymer film, 4 - photodiode array, 5 - copper block, 6 - resistance thermometer, 7 - temperature controlled jacket, (Reproduced with permission from Zywocinski, A., et al. J. Polymer Sci. Polym. Phys. 33, 595 (1995))... 

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