摘要:

AbstractCrystallization from solutions often starts in such a way that thermodynamically unstable phases appear first followed by recrystallization to thermodynamically stable phases. This empirical observation, called as Ostwald's rule of stages, is explamed here on the basis of structure changes of solutions. Experiments supporting this explanation have been carried out with aqueous solutions of citric acid, sodium hydrogen phosphate and ferrous sulphate, respectively.

ISSN:0232-1300    

DOI:10.1002/crat.2170300402

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170300403

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractConditions of synthesis, structure, and temperatures of superconducting transitions of strontium‐based mercury cuprates Hg—Sr—Me—Cu—O (Me = Ca, La, Ce, Sm, Ho) with perovskite‐like crystal structure are described. The samples belong to two homological series: HgSr2(Ln, Ce)n–1CunO2n+2 + δwith the Hg—O bond directed alongand (Hg, Cu) Sr2Lnn–1CunO2n+ 2 + δwith the (Hg, Cu)—O bond directed along. The variation of composition leads to rotation of the Hg—O bond along thehk0direction and consequently to the increase ofTcfrom 28 K to 81 K. An anomaly of the resistivity was observed around 200 K for most of the investigated samples, independent of their conten

ISSN:0232-1300    

DOI:10.1002/crat.2170300404

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractGrowth processes, structure and properties of Fe, Co, FeCo deposited alumite films have been investigated. It is shown that the magnetic characteristics depends both on alumite film parameters and properties of deposited metal (alloy) particles.

ISSN:0232-1300    

DOI:10.1002/crat.2170300405

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170300406

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractTwin structure of triclinic sodium oxalate monohydrate was determined by means of X‐ray techniques. The twin is formed by reticular pseudomerohedry, with [101] as twin axis and (101) as contact plan

ISSN:0232-1300    

DOI:10.1002/crat.2170300407

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe model is an attempt to give an explanation of polytype orderings in the crystals. Basic assumptions of the model are: the point defects play the important part in the polytype formation; these defects influence the configuration (hexagonal or cubic) of individual layers. The defects have a tendency to ordering themselves into superlattices. It acts selectively on particular stacking of the layer sequences. The results of model operation are shown in examples of experimental data of polytypic materials; they are SiC and AIIBVIcompounds.

ISSN:0232-1300    

DOI:10.1002/crat.2170300408

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170300409

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractInformation obtained owing to aquaintance with the course of the angular dependence of photoelectron intensity excited by the X‐ray standing waves allows to determine, more explicitly, the state of crystal surface layer deformation. The aim of this work is to present a new measuring device constructed at the Institute of Physics of the Polish Academy of Sciences, especially the X‐ray microcamera being simultaneously the proportional flowing counter used for measuring of photoelectron current emitted from the examined crystal. The angular dependence of the photoelectron current can be measured in coincidence with the angular running of rocking‐curves. It is possible due to a computer program controlling the X‐ray doble‐crystal spectrometer, the microcamera and the electronic system for registration of the intensity of the diffracted beam as well the flowing counter.The scheme of the X‐ray double‐crystal spectrometer, the microcamera, and the electronic measuring system operation is given. There are also given the results of the introductory measurements carried out for the Si(111) implanted with the Au ions. The calculation of rocking‐curve for non‐disturbed crystal in the case of asymmetrically cut monochromator crystal was made. There was also estimated the range of depth from that the photoelect

ISSN:0232-1300    

DOI:10.1002/crat.2170300410

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractOrthoclase‐rich alkalic feldspar crystals were grown from melts next to Orthoclase‐Albite‐Quartz eutectic composition at 2 kb in the presence of a surplus of a supercritical aqueous phase by isobaric cooling at a rate of approximately 10 °C/day. Some runs were made with KF‐bearing fluid phase, in two runs the melt was formed during intensive thermoconvection of the fluid phase. Tabular crystals were only formed from F‐bearing melts, crystals grown from F‐free melt were always fan‐shaped. We assume this fact is due to a more easy supply of Al to the growing crystal in melts

ISSN:0232-1300    

DOI:10.1002/crat.2170300411

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY