摘要:

Crystals of Ba2TiP2O9were grown from the melt by the Bridgman technique. Two types of twinning occur, namely: growth twins and mechanical twins. The growth twins form with the (100) plane as the twin plane and mechanical twins form with the (001) plane as the twin plane. In twinned crystals, growth proceeds most rapidly in the [010] direction. Rapid growth in this direction is believed to result from efficient nucleation at the re‐entrant corners formed by the ⟨310⟩ faces of the twin components. The mechanical twins form according to pseudo‐merohedral symmetry by reflection across the (001) twin plane. The angle of obliquity is 4° and the twinning shear is 0.140.

ISSN:0021-8979    

DOI:10.1063/1.1728991

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Internal friction measurements were made as a function of hydrostatic pressures up to 3 kb by use of a piezoelectric torsional oscillator inside the pressure vessel, as well as with a Marx composite oscillator both before and after pressure treatment. Specimens were prepared by cold‐working 99.99% aluminum polycrystals to a 50% reduction in width, followed by an anneal at 300°C. Measurements outside the pressure vessel showed that the strain amplitude dependence was irreversibly increased by amounts up to 1500% of the initial values as a result of the application of 3 kb for 15 min at 25°C. The original amplitude dependence was restored by annealing 15 min at 300°C. A subsequent compression again increased the amplitude dependence but to a lesser extent. After several such annealing‐compression cycles there was no irreversible effect within 4% of background. Additional cold‐work followed by annealing again produced the effect. The effect increased with increasing pressure. An increase in amplitude dependence of up to 600% also occurred in samples which had not been previously cold‐worked. The internal friction at constant strain amplitude increased faster than linearly with increasing pressure and decreased linearly with decreasing pressure. Successive pressure cycles gave the same effect but with decreasing magnitude. After about 3 cycles, both increasing and decreasing pressure gave the same linear dependence of the damping, corresponding to within 8% of the background damping. It is suggested that irreversible dislocation effects might occur as the result of shear stresses produced near voids by the hydrostatic stress.

ISSN:0021-8979    

DOI:10.1063/1.1728992

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Attempts have been made to grow single‐crystal HgS using a vapor phase growth technique. The lack of success led to the discovery of a phase transformation which occurs between the temperature of deposition and room temperature. The crystals were deposited in the cubic meta‐cinnabar form and transformed to the hexagonal cinnabar form upon cooling, with a resultant destruction of the deposited crystals. There is a large supercooling effect which seems to depend upon particle size. Upon heating cinnabar in an atmosphere of air the transformation to meta‐cinnabar occurs at 335°±10°C. Possibilities for the use of other techniques in the growth of single‐crystal HgS are considered.

ISSN:0021-8979    

DOI:10.1063/1.1728993

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The contribution of theK&agr;1&agr;2asymmetry to the total observed asymmetry is calculated for x‐ray diffraction profiles from fcc specimens containing twin faults. The profiles are approximated by exp(−k2x2), (1+k2x2)−2, or (1+k2x2)−1. Calculations, using data from filed and annealed Permalloy, show that the &agr;1&agr;2asymmetry introduces no serious error in determining the twin fault probability as long as the observations are made at values of the abscissa which correspond to at least half the distance from the profile maximum to the profile zero point. For asymmetries measured closer to the profile maximum, the &agr;1&agr;2asymmetry can become important. A method to correct for the &agr;1&agr;2asymmetry is given.

ISSN:0021-8979    

DOI:10.1063/1.1728994

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The carrier concentration homogeneity in a semiconductor can be quantitatively measured from the position of the plasma edge. This has been demonstrated for an InAs sample for which changes of homogeneity of about 0.5% have been measured. This plasma edge method for measuring carrier concentration inhomogeneities is at least an order of magnitude more sentitive than other methods reported to date and can be applied for any semiconductor that has a well‐defined plasma edge.

ISSN:0021-8979    

DOI:10.1063/1.1728995

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Propagation of waves in a transmission system consisting of a plasma column and a coaxial helix is investigated. The propagating characteristics of the structure are analyzed by a straightforward field analysis. It is demonstrated that the field solution can be reduced to a simple circuit equation describing two coupled tuned circuits. This analytical result shows that the propagation of waves in the plasma‐helix structure can be described by a purely capacitive coupling of modes between the space‐charge modes of plasma column and the helix mode. The result of this study is compared with the earlier Russian work by Bulgakovet al. The limitation of the perturbation techniques is discussed and the condition for the validity of the small perturbation assumption is given. The experimental method of separating and measuring the two coupled modes of propagation by means of mode‐selecting techniques is described.

ISSN:0021-8979    

DOI:10.1063/1.1728996

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Using a simple model, the motion of an ensemble of small conducting spheres located between two parallel electrodes is investigated theoretically in the case where the flow is space‐charge‐limited. A more realistic but more complicated model is proposed. The experimental apparatus used to check the theoretical predictions is described; agreement between theory and experiment is fair. Possible applications of such diodes are mentioned.

ISSN:0021-8979    

DOI:10.1063/1.1728997

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Anisotropic elastic stress was applied to semiconductor surfaces parallel to the plane of shallowp‐njunctions. The resistance of diffused and alloyed junctions was found to be highly stress‐sensitive under both forward and reverse bias. Reversible resistance decreases under stress by factors of more than 103were observed.

ISSN:0021-8979    

DOI:10.1063/1.1728998

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A strong external electric field in a plasma produces electrons with a temperature considerably higher than the temperature of the neutral gas in a plasma. We investigate here the currents produced by such electrons in a strong ac field. We discuss several cases of interest. Case 1 deals with the effect of a strong ac field on the plasma. It is found that the current has a component of frequency &ohgr; and a weaker component of frequency 3&ohgr;. The results are valid if &ngr;0>&ohgr;>&dgr;&ngr;0. Here &ngr;0is the collision frequency of the electrons and &dgr; is the fraction of energy transferred to the neutrals in a single collision. Case 2 deals with the effect of a strong steady electric field on which a weak ac field of frequency &ohgr; is superimposed. Here the current has a steady component plus an additional ac component of frequency &ohgr; which leads the ac field by a phase given by Eq. (33). Case 3 is similar to case 2 except that electron‐ion collisions have been considered. The measurement of the current and phases should lead to a determination of the collision frequency.

ISSN:0021-8979    

DOI:10.1063/1.1728999

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The observation of domain wall resonances by swept frequency spectrometer techniques is reported. These resonances appear as groups of very strong lines approximately 200 kc apart in the frequency range 80 to 20 Mc.

ISSN:0021-8979    

DOI:10.1063/1.1729000

出版商:AIP    

年代:1962

数据来源: AIP