Kinds Of Crystals Research Articles

Pure and doped barium titanate. Crystal growth and chemical composition

Barium titanate single crystals are grwon in two ways, i.e. by the Remeika and the Czochralski method. Doping ions (FeCoCu) are introduced into Remeika crystals and determined by a spectro photometric method. Impurity ions (FKPtSb) are determined in both kinds of crystals; pulled crystals are purer than Remeika crystals. The stoichiometry Ti/Ba + Sr is excellent in pulled crystals but the Ti, Ba, Sr, K concentrations in Cu-doped crystals show ion size effects in the compensation mechanism.

Phase‐separation phenomena in solutions of poly(2,6‐dimethyl‐1,4 phenylene oxide). II. Differential scanning calorimetry of solutions in toluene

AbstractThe phase‐separation phenomena observed in solutions of poly(2,6 dimethyl‐1,4 phenylene oxide) in toluene have been investigated by differential scanning calorimetry. These measurements supplement the experimental evidence in favor of the concept that the phase transitions observed are crystallization and melting phenomena. The experiments suggest that two kinds of crystals can develop and that a seeded crystallization is possible.

Flame Fusion Growth of Spinel and Sapphire Crystals for ESFI SOS Technology

A modified flame fusion process has been developed to grow crystals at low cost for use as substrate for the ESFI® SOS technology. Mg‐Al spinel and sapphire single crystals with diameters up to 50 mm have been grown. Differences between both kinds of crystals are described concerning the behavior during the widening phase and the cooling phase of the growth process. Crystalline perfection was investigated in both crystals by the x‐ray topography.

On the Trimorphism of 7-Hydroxy-3-(p-methoxyphenyl)-4,6-dimethyl-1-indanone

Abstract The reaction of 2′-hydroxy-4-methoxy-3′,5′-dimethylchalcone with anhydrous AlCl3 in benzene gave three kinds of crystals having different melting points. It is concluded that the crystals are three modifications of 7-hydroxy-3-(p-methoxyphenyl)-4,6-dimethyl-1-indanone on the basis of their mutal transformations, IR spectra and X-ray analysis.

The Effects of Temperature and Carbon Content on Vickers Hardness and Its Anisotropy of Iron Single Crystals

The Vickers hardness and its anisotropy of two kinds of iron single crystals were investigated at various temperatures. One kind of iron was decarburized and the other contained about 300 ppm of carbon. The hardness of the decarburized crystals decreased almost linearly with increasing temperature. The crystals containing about 300 ppm of carbon were harder than the decarburized crystals in the whole range of testing temperatures, and displayed the maximum hardness at about 400°C. The hardness anisotropy can be expressed by the following relation: H=Hacos (4θ+δ)+Hb, where θ represents the orientation of the diagonal of hardness impression, δ the phase difference, and Ha and Hb are constants depending on the kinds of crystals and on the temperature.

Formation of 3-aminophenoxazone complex by photoreaction

Photochemical oxidation of o-aminophenol was carried out in 30% ethanol or 30% dioxan solution and changes during this reaction were followed by polarography and electron absorption spectrum. Irradiation of 30% dioxan solution of o-aminophenol over a long time resulted in the appearance of a wave (E1/2=-0.85V) for separation of hydrogen peroxide, besides the reduction wave (E1/2=-0.5V) of 3-aminophenoxazone and that (E<1/2>=-1.2V) of hydrogen peroxide seen at the time of short irradiation. Oxidation products were obtained as two kinds of crystals ; crystal 1 of red needles, mp 250-251°, corresponding to 3-aminophenoxazone, and crystal 2 of deep reddish purple needles, mp 260-261°, which was found to contain 50% of 3-aminophenoxazone from the comparison of polarographic reduction wave height and E<425> nm. Since the electron spin resonance spectrum of crystal 2 was similar to that of quinhydrone, it was concluded that this product is a 1 : 1 complex of 3-aminophenoxazone and 3-hydroxy-3-aminophenoxazine.

Elaboration et caracterisation de monocristaux de V 2O 3 par transport en phase vapeur

Single crystals of V 2O 3 are obtained by HCl or TeCl 4 chemical transport method in sealed quartz tubes with temperature gradients of 1050–930°C and 990–900°C respectively. The hexagonal prims are 5 mm long and 1 or 2 mm wide. Both kinds of crystals are characterized by sharp insulator-metal transition at 156 and 137 K respectively, they present a large hysteresis. The sharp decrease in resistivity with increasing temperature is of the order of 10 8 at the transition.

The Variation of Vaporization Rates with Orientation for Basal Planes of Zinc Oxide and Cadmium Sulfide

The metal (0001) basal faces of hexagonal (wurtzite) modifications of both zinc oxide and cadmium sulfide are shown to vaporize at higher rates than the nonmetal (0001̄) faces. The difference in rates has been measured for cadmium sulfide as a function of temperature. Surface morphologies also differ between opposite basal faces of both kinds of crystals. The data suggest that desorption may be rate limiting.

Electronic and Vibrational Excitons in Molecular Crystals

This review is the third in the Annual Reviews of Physical Chemistry (1) during the past eight years that treats the optical properties of molecular crystals. Two other reviews (2) on this same type of subject matter, but with slightly different emphasis, have appeared recently in the literature. Besides these review articles, other recent treatises are strongly recommended to the reader. Knox's book (3) , for example, presents a much broader presentation of exciton theory and practice than this review attempts to do. For those readers who are interested in a unified approach, not just to the Frenkel exciton problem in organic crystals, but also to other kinds of excitons in other kinds of crystals, Knox's book is strongly recommended as a starting point. A condensed but rather clear discussion of many of the important aspects of space group theory and time reversal symmetry as they apply to the general energy band problem is to be found in the book by Callaway (4) . Other good sources for this type of information are the classic paper by Koster (5) and the books on applied group theory by Tinkham (6) and Mariot (7) . Craig & Walmsley (8) outline the fundamental theoretical material neces­ sary for an understanding of the subject matter presented in this review. A fairly recent paper by Davydov (9) corrects, clarifies, and extends Davydov's own classical work on the molecular exciton problem. Because of the exist­ ence of this publication, the original book in Russian ( 10) and its later English translation ( 1 1 ) , which describes Davydov's early work, are now to be valued more for their historical content and bibliographies than as a source for study of modern molecular exciton theory. Since Hochstrasser's review, a large number of new experimental and theoretical techniques have been introduced leading to many significant advances in molecular exciton theory. The field is a much more polished one than it was in 1966, and its scope is considerably broader. The field too has taken on new significance in recent years because of the partial shift of

Evidence for Photochemical Changes in Traps in CdS Crystals

The dependence of trap filling on the intensity, temperature, and wavelength of the photoexcitation has been investigated for trapping centers in S–Se-annealed CdS–CdSe crystals and in crystals of CdS subjected previously to electron radiation damage and photoexcited annealing. For certain traps in both these kinds of crystals, it was found that trap filling was not only critically dependent on the temperature of excitation but also on the wavelength of excitation. In fact, for each process observed, a band of wavelengths is most effective, the maximum wavelength of this band being larger than the wavelength for maximum photoconductivity. This result makes previous attempts to explain this kind of phenomenon in terms of a Coulomb-repulsive trap less acceptable and provides additional evidence for the presence of photochemical changes at and below room temperature in CdS-like materials.

Introductory remarks

The first protein crystal from which single crystal X-ray diffraction spectra were obtained was a large crystal of the proteolytic enzyme, pepsin. The experiments began, as many protein researches begin, in the laboratory of Arne Tiselius at Uppsala. John Philpot was visiting there for a period in 1934 to work with Tiselius on methods for purifying proteins: the protein he chose to operate on was pepsin. Of this he grew very large crystals—2 mm across—by accident, through leaving his preparation in the refrigerator while he was away on a skiing expedition. He showed the growing crystals to Glyn Millikan, then visiting Uppsala from Cambridge, and Millikan, knowing of Bernal’s great interest in all kinds of crystals and also in biological problems, asked for, and was given, a supply to take back to Bernal in Cambridge. He carried the test-tube containing the crystals as they were, growing in their mother liquor. This enabled Bernal to observe that a single crystal shrank and lost birefringence and order on removal from its mother liquor; he therefore tried taking X-ray photographs from crystals still surrounded by their liquid of crystallization.

Predicting some Effects of Lattice Vibrations on Proton Scattering Patterns

AbstractA method of predicting the approximate relative intensities of lines in proton blocking patterns recently proposed, which is based on summing the squares of structure factors for the various orders of reflection of a plane, is found to predict certain effects of lattice vibrations on the lines in some recently reported patterns. The mean square amplitude of vibration enters the calculations through a Debye-Waller temperature factor like that used in X-ray diffraction. When patterns are compared for groups of crystals that are nearly identical except for this temperature factor, the qualitative predictions by this method agree with the observations. If it is also arbitrarily assumed that the integrated intensity dip at a spot where lines intersect is approximated by summing the calculated Integrated intensity dips for all of the lines crossing at the spot, one has a simple and convenient method of predicting relative spot intensities. Such calculations have been successful in establishing the order of decreasing intensity for most of the spots along a given line, with several different kinds of crystals. This method also serves to predict qualitatively how prominent the spots appear relative to the lines, in general, in patterns of crystals that differ appreciably only in the amplitude of the thermal vibrations.

Synthesis of 9H-pyrimido[4,5-b]indole derivatives

The Vilsmeier reaction of 2-benzyloxycarbonylamidoindole (I) afforded 2-benzyloxycarbonylamido-3-formylindole (II) and N-(3-formyl-2-indolyl)-N', N'-dimethylformamidine (III). Various kinds of 3 acylindole derivatives were synthesized by the same reaction. Reaction of II with benzylamine easily effected condensation-cyclization to produce 3-benzyl-2-oxo-2, 3-dihydro-9H-pyrimido [4, 5-b] indole (VIIa). In order to further extend this reaction, reaction of various 3-acylindole derivatives with various primary amines was carried out and 9H-pyrimido [4, 5-b] indole derivatives listed in Tables I and II were synthesized. Benzylation of VIIa gives two kinds of crystals and it was established that these correspond to 3, 9-dibenzyl-(XL) and 1, 3-dibenzyl-pyrimido [4, 5-b] indole derivatives (XLI) from their elemental analytical values, infrared and nuclear magnetic resonance spectra, and their synthesis by a different route.

The Effects of Irradiation of 100 keV Electrons on Alkali Halide Crystals; The Point Defect Coagulates in NaCl and KCl Irradiated at Room Temperature

Thin films of KCl and NaCl single crystals prepared by chemical polishing were examined by an electron microscope. During the observation, the thin films were damaged by electron beam used for the image formation. As a result of electron irradiation at room temperature, plate shaped defects parallel to one of the {100} planes and elongated in one of the directions were formed in both kinds of crystals. The maximum dimension of them was about 1 µ in long axis 1000∼3000 A in short axis and ∼100 A in thickness. It is supposed that these plates correspond to the small alkali metal colloids which were considered to be the origin of X-band absorption in the optical measurement, because the behaviour of the plates during heat treatment between room temperature and 300°C showed good agreement with that of the colloids.

Studies on Syntheses of Thiohydantoin Related Compounds. XVII. Synthesis of 1, 3-Diphenyl-5-butylhydantoin

1, 3-Diphenyl-5-butylhydantoin (I) was synthesized by two methods, indirect and direct, with the object of the development of a new analgesic agent. In the course of the indirect method, treatment of 1, 3-diphenyl-2-thiohydantoin (IV) with n-butylaldehyde gave 1, 3-diphenyl-5-butylidene-2-thiohydantoin (V) as two kinds of crystals, which were confirmed to be geometrical isomers with each other. The configurations of them were determined from the NMR spectral data. Two by-products obtained in this reaction was also geometrical isomers with each other, and they were deduced to be dimers of 1, 3-diphenyl-5-butylidene-2-thiohydantoin, 1, 3-diphenyl-5-{β-ethyl-γ-(1, 3-diphenyl-2-thiohydantoinyl)} hexylidene-2-thiohydantoin (Xa and Xb) from some physical data. In the direct method, 1, 3-diphenyl-5-butylhydantoin was obtained in 40% yield by refluxing 2-anilinohexanoic acid (IX) and phenyl isocyanate in xylene.

Misroscopic observation of phase transitions of ammonium nitrate

Phase transitions IV ⇌ II, IV ⇌ V and II ⇌ V of ammonium nitrate were observed through a polarizing microscope by using thin single crystals of various orientations. In the transition II ⇀ IV, a single crystal is split into two kinds of crystals, in which the direction of the c-axes is common but the a- and b-axes are interchanged. A composite pattern appears which is characteristic of the orientation of the initial crystal. The crystal composites have boundaries of {110} planes, which may be twinning planes. On the reserve transition, the composites are unified again. In both transformations, the new phase grows in a specified direction in the mother crystal in conformity with a minimum strain postulate. The IV ⇌ V transitions are very similar to the IV ⇌ II transitions except for the appearance on occasions of a faint chiaroscuro pattern of phase V. This pattern is probably due to the formation of microtwins. The II ⇌ V transitions occur as a second order transition in minute crystals within a temperature range from about 44°C to 41 °C. The transformation has been detected only by the same chiaroscuro pattern of phase V in some crystals as in the case of the IV ⇀ V transition. The observed transition phenomena are discussed on the basis of the crystal structures of the polymorphs of ammonium nitrate.

The Effect of Fast-Neutron Irradiation at Ambient Temperature on the Lattice Parameters of Silicon and Germanium Crystals

The change in the lattice parameter of nearly perfect silicon and germanium crystals irradiated with 4.2 \ifmmode\times\else\texttimes\fi{} ${10}^{19}$ fast neutrons/${\mathrm{cm}}^{2}$ at about 40\ifmmode^\circ\else\textdegree\fi{}C has been measured. The results show an expansion $\frac{\ensuremath{\Delta}a}{a}$ equal to about 1 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}4}$ in both kinds of crystals. Isochronal annealing experiments on irradiated germanium indicate at least two well-defined annealing regions centered at 150 and 400\ifmmode^\circ\else\textdegree\fi{}C, coinciding with previous anomalous x-ray transmission experiments.

Use of Anomalous X-Ray Transmission for the Detection of Defects Produced in Silicon and Germanium by Fast Neutron Irradiation

Absolute x-ray intensities anomalously transmitted through fast-neutron-irradiated silicon and germanium crystals have been measured and compared with those transmitted through nearly perfect (unirradiated) crystals. The results indicate that the Borrmann intensities in both silicon and germanium irradiated with 4×1019 fast neutrons/cm2 (E&amp;gt;0.6 MeV) were reduced by nearly a factor of two for μ0t0≈30. In contrast, very small (&amp;lt;5%) decreases in the Bragg intensities diffracted from the surfaces were observed. The observed decreases in intensity have been attributed to the strains in the vicinity of ``disordered regions,'' previously observed in electron-microscopy studies of irradiated germanium. Isochronal annealing studies have demonstrated that the crystals could be restored to near their original state of perfection by heating to ≈700°C for 30 min. Two well-defined annealing peaks were found in both kinds of crystals, silicon annealing at about 190° and 630°C, and germanium at about 150° and 400°C. These studies suggest that fast-neutron doses at ambient temperature in the range of 1019–1020/cm2 (E&amp;gt;0.6 MeV) are necessary for observations of appreciable effects on the x-ray intensities diffracted from silicon and germanium.

へテロ環化合物の研究(第3報) : Methyl 5-(2-Phenylvinyl)-2-furoate類の合成

Derivative of methyl 5-(2-phenylvinyl)furoate, substituted with mononitro group in the benzene ring, was synthesized and its ester was hydrolyzed and derived to an acid amide. In the preparation of methyl 5-[2-(ο-nitrophenyl)vinyl]furoate, two kinds of crystals, considered to be cis and trans isomers, were obtained. Each was derived to the acid amide by the usual method but there was no evidence for cis-trans conversion during this reaction. Decarboxylation of the corresponding carboxylic acids gave the same substance, suggesting the cis-trans conversion to take place during this reaction.

Gas Chromatographic Analysis of 2-(2-Furyl)-3-(5-nitro-2-furyl) acrylamide.

A sensitive and specific analysis has been developed for 2-(2-furyl)-3-(5-nitro-3-furyl) acrylamide (Furylfuramide) utilizing gas chromatography (GLC) with hydrogen flame ionization detector (FID) and electron capture detector (ECD). The separation of the trans and cis isomer by direct injection was established using the column paking of 1.5% QF-1 on Anakrom at 200°with nitrogen as carrier gas. In analysis of Furylfuramide these isomers must be identified, and so it seemed that GLC determination was more suitable than chemical methods using spectrophotomeric absorption. Sensitivities obtained were 1γ(FID) and 0.01γ (ECD). Moreover, it was definitetly cleared that cis type of Frylfuramide had two kinds of crystals, α-form (m.p. 160°) and β-form (m.p. 185°), and the transition from α-form to β-form occurred at 160°.