ISSN:0232-1300    

DOI:10.1002/crat.2170200127

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractIn the Czochralski method, the effect of ultrasonic vibrations on the growth of InSb single crystals was investigated by observing the growth morphology. Remarkable changes which ultrasonic vibrations brought about were: (1) the crystal diameter, (2) the width of the facet region and (3) the inclined angle of non‐facet interfaces near the facet region for the (111) plane. After introducing vibrations, the crystal diameter decreased smoothly with growth time. However, both the facet width and the inclined angle reached each minimum value after 5 to 7 min regardless of the magnitude of vibrational output powers from 30 to 90 W, and they were in roughly proportional relation with each other. The change rates of crystal diameter and of facet width increased with vibrational powers. The decrease of crystal diameter was known to result from the rise of the melt temperature, which was brought by both the mixture of the melt and the thermal energy transformation due to ultrasonic vibrations. The change of facet width depended upon the melt flow itself in addition to the temperature ris

ISSN:0232-1300    

DOI:10.1002/crat.2170200102

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170200128

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170200129

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractFerrierite, a medium‐port molecular sieve zeolite, was synthesized as the only crystalline phase from an aqueous gel of composition 1.6 Na2O · 1.6 K2O · Al2O3· 13.5 SiO2· 130 H2O · 0.8 CO2· 2.4 (HCO2)2at 250 °C in reaction periods ranging from 40 to 95 hours. The crystallization time was reduced with seeding. Ferrierite was a metastable phase in this system and it transformed into tridymite, high sanidine and orthoclase at longer reaction periods. At 200 °C, chabazite was crystallized from the same batch composition at a very slow rate. At temperatures higher than 250 °C and in the absence of carbonates and bicarbonates in the batch mixture, tridymite, high sanidine and orthoclase crystallized directly without the formation of ferrierite. The synthetic ferrierite sorbs benzene, toluene and cyclohexane and behaves as a medium port molecular sieve. The sorption capacity of ferrierite was improved by acid treatments with no deterioration of the crystal

ISSN:0232-1300    

DOI:10.1002/crat.2170200103

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170200131

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170200105

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractIn order to meet requirements for the preparation of low dislocation density GaAs single crystals a horizontal Bridgman type apparatus was designed. Construction of the apparatus allows the establishment of enhanced temperature stability of the arsenic source and hence better stability of the arsenic vapour pressure during the growth. This effect was achieved without application of heat pipes which are usually used for the improvement of thermal profile and temperature stability. The influence of different arsenic vapour pressures on the density of dislocations was confirmed in the course of this work.

ISSN:0232-1300    

DOI:10.1002/crat.2170200106

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170200107

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractEtch structures obtained by HF etching on habit and cleaved rhombohedral surfaces of synthetic quartz grown by hydrothermal crystallization technique, indicative of twinning in them are described, illustrated and discussed. The twin traces appear in the form of lines of dis‐continuity in [1121] and [1211]directions. Etch pits within the parallelogram‐shaped bound areas are oppositely oriented with respect to those on the rhombohedral surface of the main crystal. The form of twinning observed is found to be of parallel lattice type and the surface within and outside the bound areas are coplanar in most of the cases. The rhombohedral faces of the twinned crystals are found to be geometrically related to each other as if one part is derived from the other by a rotation of 180° about [1210] direction.Discontinuation in the crystal lattice along the twin trace is evidenced by obstructions in the normal development of an etch pit. Deep penetration of twin traces and parallelogram‐shaped regions, enclosing etch pits of opposite orientation (twinned areas), well within the crystal structure is demonstrated by comparison of etch patterns on matched rhombohedral cleavages and the results on their successive etching. The type of twinning displayed by the crystals is discussed in the light of models suggested. Causes for the generation of twinning in synthetic quartz are explained to lie in the availability of twinned nuclei in the seed plates used for hydrothermal crystallization of

ISSN:0232-1300    

DOI:10.1002/crat.2170200108

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY