Bulk modulus — volume relationship in alkali halides with rocksalt structure

It is shown that the bulk modulus of the alkali halides with rocksalt structure follows the simple relation B = b₀(1 — b₁f_c) V where V₀ is the unit cell volume, f_c the spectroscopically defined covalency of the chemical bond, and b₀, b₁, and n are constants having the same values for all compounds. This result is compared with the bulk modulus scaling law found for the tetrahedral semiconductors.     

Microhardness of tetrahedrally bonded elemental and binary semiconductors

An analysis of experimental microhardness data shows that the microhardness at room temperature of the diamond, zincblende and wurtzite structure compounds follows the simple relation H = h_oa^−xT_m(1 –g_of_i) where a is the lattice parameter T_m the melting temperature, f_i the spectroscopically defined bond ionicity and h_o, x, and g_o are constants having the same values for all compounds. The close relation between microhardness and bulk modulus is discussed.     

Synthesis and Characterisation of Bulk Textured Phases in the Bi(Pb)—Sr—Ca—Cu—O System

Growth of lead-doped textured Bi-cuprate, using an immersed heater floating zone (TSFZ) apparatus, from a narrow supercooled melt created an essentially dense structure consisting of locally aligned long platelet crystal grains. The extended grains have their long axes parallel to the growth axis with a low angle misorientation. The effect of gas bubbles and the pulling rates on the microstructure and superconducting transition temperature of the textured boules have been studied. The decomposing nature of the 2223 phase on melting leads to form the energetically favourable low T_c 2212 phase.     

Positron annihilation study of defects and microheterogeneity of chalcogenide glassy semiconductors — chemical bonding in ge—se and some AVBVI systems

Recently developed ideas on the mechanisms of positron annihilation in chalcogenide glassy semiconductors are used in studying chemical bonding of the A^VB^VI structures (A = As, B = S, Se, Te) and Ge Se.     

Coefficient of volume expansion and thermoacoustic parameters in certain alkoxy benzylidene butylanilines — IB

Using the coefficient of volume expansion certain thermoacoustic parameters like isobaric (K), isothermal (K″), isochoric (K″) acoustic parameters, free volume (V_a/V) and two new dimensionless acoustic parameters A* and B* are estimated in certain alkoxy benzylidene butylanilines, in their isotropic- and mesophases as well as at and in the immediate vicinity of the phase transition temperatures following the method which was suggested by Sharma, for non-mesomorphic systems.     

Study on the Phase equilibrium in the Systems Sodium Selenate — Cadmium Selenate — Water and Sodium Selenate — Manganese Selenate — Water at 25 °C

The phase equilibrium in the systems Na₂SeO₄ CdSeO₄ H₂O and Na₂SeO₄ MnSeO₄ H₂O were studied and it was established that new phases were obtained — double salts with a composition: Na₂Cd(SeO₄)₂ · 2 H₂O and Na₂Mn(SeO₄)₂ · 2 H₂O. The fields of phase equilibrium of the double salts in the triple systems were determined. The composition of the new phases and the number of the water molecules of crystallization were investigated, respectively by the Schreinemackers' method of physico-chemical analysis and thermogravimetrical analysis. An X-ray diffraction analysis of the new phases obtained was done.     

Thick LPE Layers of InAs1—xSbx for 3—5 μm Optoelectronic Applications

N-InAs_1—xSb_x/n, p-InAs heterostructures were grown by liquid phase epitaxy on (100) oriented substrates. The layer composition was varied in the interval 0 < x < 0.1, the corresponding lattice mismatch being not greater than 0.5%. The layer composition was studied by microprobe analysis on the surface of the structure cross-section. Microhardness profiles were investigated using Vickers and Knoop indentors. Raman scattering was also studied.     

Neutronographical investigations of the age hardening behaviour on Iron — Manganese — Nickel alloys

Age hardenable martensitic Iron—Manganese—Nickel alloys were neutronographically investigated in order to explain the age hardening effect occurring during the heat treatment. The formation of coherent precipitations of an ordering phase within the matrix proved to be the reason for the occurring hardness increase.     

Static fatigue in glass — A reappraisal

The delayed failure of soda-lime glass was tested after different surface and heat treatments and at different humidities. It was found that the treatment history of the glass strongly influenced the characteristics times of failure and the effect of humidity on these times. However, the functional dependence of log failure time on relative stress was similar for most treatments. Analysis of the distributions of failure times at particular stresses showed that the log failure time was not linear with applied stress, as often assumed. The experimental data fit better inverse proportionality between log time and relative stress. Analysis of previous data on crack propagation (‘K - ν curves’) in glass also showed this proportionality. Some theoretical reasons for these results are examined.     

Chemistry of organic eutectics: Phenanthrene — benzoic acid and phenanthrene — cinnamic acid systems

Solid-liquid equilibrium data for binary systems of phenanthrene with benzoic acid and cinnamic acid, expressed in the form of temperature-composition curves, show the formation of a simple eutectic in each case. Linear velocity of crystallisation (v), studied by capillary method at different undercoolings (ΔT), suggests the applicability of Hillig-Turnbull equation, v = u(ΔT) ⁿ, where u and n are constants depending on the nature of solidification. Data on heats of fusion of pure components and eutectics, determined by the DTA method, infer appreciable interaction among the components in the eutectic melts. To highlight the nature of interactions among the components forming the eutectic melt, the excess thermodynamic functions such as h^E, s^E, and g^E were computed. Microscopic studies reveal that the structure of eutectic is different from those of the parent components. Infrared spectra, recorded in the region, 4000 —625 cm⁻¹, indicate weak interactions among the components in the eutectic.     

The Crystal and Molecular Structure of 11,12‐dibromo‐ 7,8—benzo‐1,5‐di(p—tolylsulphonyl)‐1,5‐diazacyclononan

The crystal structure of the title compound, C₂₅H₂₆Br₂N₂O₄S₂ was determined by single crystal X‐ray diffraction technique. The crystals are monoclinic, space group C 2/c, with a=20.7142(2) Å b=11.7910(2) Å, c= 10.6735(3) Å, β=98.549(2)°, V=2577.94(9) ų, Z=4. The structure was solved by direct methods and refined by least‐squares methods to a final R=0.046 for 1866 observed reflections with I>2sigma(I). The title compound, displays disordered geometry around the C1 atom located almost on twofold axis. The nine‐membered heterocylic ring is close to the half‐chair conformation. The dihedral angle between phenyl rings is 34.2(1)°.     

Growth rate dispersion — a review

The growth rate dispersion (GRD) is reviewed from its start up to today. A definition is given followed by a summary of the facts and the first approaches for explanations. This all are surface reaction steps. The discussion of the consequences – no size dependent growth – is carried through. At the end the models (RF-and CCG-model) will be introduced which make it possible to work with the growth rate dispersion instead of size dependent growth. The newest approach is the superpositioning of the two models, this is perhaps the most promising way.     

Isothermal changes of volume and Young's modulus of amorphous CoP

The isothermal shrinkage and the isothermal increase of Young's modulus E of electrodeposited CoP samples were studied in the amorphous state and during crystallization. The lower limit of the activation spectrum of the elementary processes responsible for these changes is shifted from 0.8 to 1.6 eV by annealing at temperatures ascending from 100°C to 220°C. From the Arrhenius equation a frequency constant of 10^9.5±2.5 was derived.On account of the different behavior of the two properties we conclude that the changes of E in connection with the relaxation of the amorphous structure is mainly a consequence of the homogenization of the material and the shrinkage is mainly a consequence of the annihilation of free volume. Based on the observations a model is proposed concerning the nature of the elementary processes involved in the different steps of structural relaxation. During crystallization the correlation between the increases in Young's modulus and in density is totally removed. These results show that the observation of temporal and thermal changes of only one physical property does not yield full information about the kinetics of structural relaxation and crystallization.     

Dielectric Properties of Superionic System AgBr—PbI2—Ag2O—B2O3

Dielectric properties of the system AgBr—PbI₂—Ag₂O—B₂O₃ has been studied for various temperatures and frequencies. Conductivity of the sample has also been measured and it is found that at 160 °C it attains the value 5.9 × 10^—3 (Ohms cm)^—1 and the activation energy calculated from the Arrhenius is found to be 0.16 eV.     

Synthetic Diamond — Basic Research and Applications

Non-equilibrium growth of synthetic diamond layers by chemical vapour deposition (CVD) techniques on heterosubstrates has largely been improved over the past decade. On silicon substrates highly textured and oriented diamond films can be grown with optical transparencies and thermal conductivities suitable for broad-band optical windows and heat spreaders. Boron pulse-doping of homoepitaxial diamond layers leads to high p-conductivity at room temperature allowing the fabrication of Schottky diodes and field effect transistors operating at temperatures up to 1000 K. Other devices such as sensors and detectors are being successfully fabricated. At the same time many basic questions remain to be solved including efficient n-type doping.