Single Bridgman

All static studies at pressures beyond 25 GPa are done with diamond-anvil cells conceived independently by Jamieson [32] and by Weir etal [33]. In these variants of Bridgman s design, the anvils are single-crystal gem-quality diamonds, the hardest known material, truncated with small flat faces (culets) usually less than 0.5 nun in diameter. Diamond anvils with 50 pm diameter or smaller culets can generate pressures to about 500 GPa, the highest static laboratory pressures equivalent to the pressure at the centre of the Earth. 

TJItrahigh (99.999 + %) purity tellurium is prepared by zone refining in a hydrogen or inert-gas atmosphere. Single crystals of tellurium, tellurium alloys, and metal teUurides are grown by the Bridgman and Czochralski methods (see Semiconductors). 

Top Bridgman procedure for the production of large single crystals. From a eutectic melt one can obtain a single crystal with embedded wires. Bottom possible subsequent steps of processing... 

As early as 1923, Bridgman had observed that the compressibility of metals is proportional to their molar volume raised to Anderson and coworkers (cf Anderson, 1972, and references therein) extended Bridgman s empirical relationship to various isostructural classes of compounds, noting that, within a single isos-tructural class, the following relation is valid ... 

Fig. 3.45 Horizontal Bridgman apparatus for growing GaAs single crystals. ...

The Bridgman and Czochralski (LEG) methods as mentioned above, are useful for growing GaAs single crystals, from the viewpoint of practical applications. The following methods tried or proposed by many workers are... 

M. Sugimoto Magnetic Spinel Single Crystals by Bridgman Technique (24 ref.)... 

It is also possible to produce single-crystal ingots as well as highly oriented textured polycrystalline materials (i.e., those in which the grains exhibit a preferred orientation) by directional solidification. With the Bridgman technique... 

Figure 2. Three spatial scales for modeling melt crystal growth, as exemplified by the vertical Bridgman process. From Theory of Transport Processes in Single Crystal Growth from the Melt, by R. A. Brown, AJChE Journal, Vol. 34, No. 6, pp. 881-911, 1988, [29]. Reproduced by permission of the American Institute of Chemical Engineers copyright 1988 AIChE.

The next step is to produce nearly perfect single-crystal boules of silicon from the ultrapure polycrystalline silicon. Many techniques have been developed to accomplish this, and they all rely on a similar set of concepts that describe the transport process, thermodynamically controlled solubility, and kinetics [8]. Three important methods are the vertical Bridgman-Stockbarger, Czochralski, and floating zone processes, fully described in Fundamentals of Crystal Growth by Rosenberger [9]. 

Earlier investigations on N20 have been summarized by Herzfeld and Litovitz [8] and by Calvert [252]. Simpson, Bridgman, and Chandler [253] have more recently examined vibrational relaxation in pure N20 over the range 320-820°K using shock-tube interferometry. As in the case of C02, single relaxation is observed. Experimental relaxation times are depicted in Figure 3.31, and are compared with SSH theory. 

Fig. 33. Polarized emission spectra of single-crystal Ba[Pt(CN)4] 4 H20 at different hydrostatic pressures (T = 295 K)133). The emission intensities at different pressures cannot be compared. The excitation wavelength was varied with pressure to fit approximately the maximum of the E c polarized reflectance. For the high pressure investigations a modified sapphire cell of Bridgman s opposed anvil type was used. The pressure was determined by the amount of red-shift of the Rt- and R2-lines167) of ruby crystals placed around the sample...

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