Polycrystalline solids transparent

Any inclusions in the parent material that have a different refractive index— such as air holes and precipitate particles—are accounted for by the Sim term. In processes for making ceramic polycrystalline materials transparent, reducing this term is of particular importance. Since transparent ceramic polycrystalline materials are synthesized at high temperature in the solid state, diffusion phenomena in the material constitute the basic process for eliminating air holes from the polycrystalline material. The sintering parameters include the molding conditions, sintering temperature, time, atmosphere, pressure and additives, and must be precisely controlled. 

Thermal uniformity in the cold zone was found to be from 0.01 to 0.02 °C, and that in the hot zone was found to be better than + 0.5 °C vertically and + 0.1 °C horizontally. Thermal gradients near the solid-liquid interface were achieved in excess of 30 °C cm " in the crystal region and up to 20 °C cm" in the melt. The growth of crystals was performed in a sealed transparent silica ampoule, which has two rooms for As source and GaAs polycrystalline, respectively, separated by a quartz diffusion barrier. For details of the growth process the reader is referred to Ref. 43. In this experiment the As source temperature T. was systematically reduced by 2 °C at 3 h intervals from 620 °C to 614 °C. 

When acidic (pH 3 to 4) mixed solution containing 0.08 M CdCl2 and 1 M NH4SCN (or KSCN) is heated, the solution remains clear because no chemical solid formation takes place. When ITO glass or polycrystalline Ni substrates are cathodized at -0.7 V (vs. SCE) in this solution, although very slowly compared to CBD or ETCD, transparent yellow thin films grow. Film thickness increased... 

A.lkesue, 1, Furusato and K. Kamata, Polycrystalline Transparent YAG Creamics by a Solid-state Reaction Method, J. Am. Ceram. Soc., 78, 225-8 (1995). 

Ikesue A, Eumsato I, Kamata K (1995) Fabrication of polycrystalline transparent YAG cramics by solid-state reaction method. J Am Ceram Soc 78 225-228... 

Fig. 2.28 Transparency of the Sri+ (/2Al2+ (Si2-x08 (0 x 0.4) polycrystalline ceramics, a Transmission spectrum measured on the sample with x = 0.2 (Sr11Al2.2Si1.gOg) at a thickness of 1.5 mm. The n = 1.59 refractive index implies a 90.1 % maximum theoretical transparency dashed line), b Photograph of the same material illustrating the almost perfect 90 % transparency, c Photograph of the Sri+ c/2Al2+ cSi2- c08 (x = 0, 0.1, 0.2, 0.3, and 0.4) polycrystalline ceramics showing transparency evolution along the reported solid solution. Reproduced with permission from [275], Copyright 2015, American Chemical Society...

Sutorik AC, Gilde G, Swab JJ, Cooper C, Gamble R, Shanholtz E (2012) Transparent solid solution magnesium aluminate spinel polycrystalline ceramic with the alumina-rich composition MgO-1.2 AI2O3. J Am Ceram Soc 95 636-643... 

Lee SH, Kochawattana S, Messing GL, Dumm JQ, Quarles G, Castillo V (2006) Solid-state reactive sintering of transparent polycrystalline Nd YAG ceramics. J Am Ceram Soc 89 1945-1950... 

Solids that have a phase transition between colored/noncolored, transparent/ opaque, or amorphous/polycrystalline phases. 

Polycrystalline or powdered samples can be prepared as a suspension in mineral oil (Nujol mull), as a potassium bromide disk (pellet), or as thin films deposited on infrared-transparent substrates. The potassium bromide pellet is the most common way of preparing powder samples in this method a small amount, usually 1 mg, of finely-ground solid sample is mixed with powdered potassium bromide, usually 300 mg. and then pressed in an evacuated die under high pressure. The resulting disks are transparent and yield excellent spectra. The only infrared absorption in the potassium bromide matrix is due to small amounts of adsorbed water, which can. however, be confused with OH-containing impurities in the sam-... 

The origin of the problem is demonstrated by Fig. 1 showing typical UV-Vis-spectra observed for a solid single-crystal PDA "as polymerized", the same PDA dissolved to a dilute monodisperse solution and reprecipitated to a thin, transparent polycrystalline film (1). The two peaks observed for a partially polymerized single crystal of PTS-12 (1) with Xjnax 535 nm belong... 

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