摘要:

The Curie point of KD2PO4is found to be 222°±1°K, which is 9°K higher than previously reported. It is believed that the higher value is due to more complete deuteration. Other physical properties (at room temperature unless otherwise noted) are as follows: dielectric constant from 208° to 300°K; contour shearmode resonance‐frequency constant from 270° to 320°K; elastic compliance,s66E=165±3×10−12m2/N; piezoelectric constant,d36=58±2×10−12C/N; electromechanical coupling,k36=0.22±0.01; optical absorption between 200 and 2600 m&mgr; for both KD2PO4and KH2PO4(the transmission of a 7.4‐mm‐thick KD2PO4sample was greater than 50 percent from 400 to 1850 m&mgr;); zero stress electro‐optic coefficient,r63=26.4±0.7×10−12m/V; lattice constants for both KD2PO4and KH2PO4; and spontaneous polarization and coercive field from 150° to 222°K.

ISSN:0021-8979    

DOI:10.1063/1.1729696

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The dispersion of the magnetic anisotropy was monotonically increased in several Ni&sngbnd;Fe films by subjecting them to increasingly severe heat treatments, and the room‐temperature magnetic properties were monitored after each anneal by Lorentz electron microscopy. A gradual transition towards increasingly anomalous properties in a single film was thereby observed. An increase, with annealing, of the magnetization ripple intensity, the measured angular anisotropy dispersion, and the wall coercive forceHwwas found. After sufficient annealing, locking was seen upon reversal parallel to the easy axis; further annealing increased the locking‐wall density. The anisotropy fieldHkmonotonically decreased with annealing until the uniaxial character of the film was lost and it became a rotatable‐initial‐susceptibility (RIS) film. Reversal at azimuths away from the easy axis proceeded by labyrinth propagation after the early anneals, but by partial rotation after more severe annealing.

ISSN:0021-8979    

DOI:10.1063/1.1729697

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Rapid diffusion along dislocation cores generally enhances the average bulk diffusion in a dislocated crystal. If each diffusing atom has at least several opportunities to make rapid excursions along various dislocation cores, Hart has shown thatDT/DT0= 1+fDP/DT0.DTis the average bulk diffusivity,DT0is the diffusivity in the dislocation‐free lattice,fis the fraction of atoms in dislocation pipes, andDPis the diffusivity along dislocation pipes. Under these conditions, the diffusion‐penetration is increased by the short‐circuiting but the general shape of the penetration curve is unaffected. When the dislocations are static, each diffusing atom must visit a number of dislocations, and a necessary condition for the Hart relation to hold is 2(DT0t)½>ld, wheretis the diffusion time, andldis the dislocation spacing. When this condition fails (for example, at lower temperatures), and when the dislocations are static, it is demonstrated that the amount of short‐circuiting is greatly reduced and that the dislocations become essentially ``clogged.'' However, if the dislocations move through the crystal, as they do in plastic deformation, the situation is quite different, since in this case the dislocations may visit the diffusing atoms rather than vice versa. In such cases, the short‐circuiting may again be randomized and the enhancement can be as large as (but no larger than) the result given by Hart, even if 2(DT0t)½<ld. In certain cases, this type of short‐circuiting can produce very large relative enhancements.A parallel development is given for short‐circuiting due to grain boundaries. In particular, it is shown that grain boundary migration and recrystallization, which occurs repeatedly during deformation of metals with low stacking fault energy, can, for temperatures equal to or less than about half the melting temperature, lead to a greatly increased diffusion coefficient without altering the general shape of the penetration curve.A number of the results established in this work (Part II) are used in Part III (to be published) where a comprehensive interpretation of recent experimental work in the field is carried out. Part I consists of an analysis of point defect models for strain‐enhanced diffusion.

ISSN:0021-8979    

DOI:10.1063/1.1729698

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Polycrystalline black phosphorus has been produced by the Bridgman method of combined temperature and pressure and found to beptype with room‐temperature resistivity around one &OHgr;‐cm, in agreement with the observations of previous workers. From 300° to 700°K, the resistivity can be fitted by an expression &rgr;av=4.6×10−3exp(0.35/2kT) &OHgr;‐cm, and the Hall data by (ReT32)−1= constant exp(−0.34/2kT). The productR&sgr; can be represented in this temperature range by (R&sgr;)av= 9×105T−1.4cm2/V‐sec. The deviation from this law toward lower mobility observed by Keyes from 250° to 350°K does not occur in these samples. The resistivity continues to rise even near liquid‐helium temperature, and maxima in the Hall coefficient occur between 24° and 30°K. The low‐temperatureR&sgr; products also exhibit maxima, and the magnitude of this product is small near liquid‐helium temperature. Although these characteristics are consistent with two‐band conduction, the relative appearance of the two sets of maxima is not consistent with a prediction of the simplest two‐band theory. An optical absorption edge is found in the 2‐ to 6‐&mgr; region and its temperature dependence yieldsdW/dT= 2.8×10−4eV/deg. A sharp absorption peak observed near 21 &mgr; moves to longer wavelengths with increasing temperature at a ratedW/dT= −2×10−6eV/deg. At helium temperature the ac photoconductive response is substantially flat from one to 20 &mgr;. At nitrogen temperature the response is peaked between 4 and 5 &mgr;, while at room temperature a peak is observed in the same wave‐length range but the sensitivity is considerably less.

ISSN:0021-8979    

DOI:10.1063/1.1729699

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The effects of moving striations in a glow discharge on microwave standing‐wave patterns in a waveguide containing the discharge were measured. The data yielded estimates of the longitudinal variation of electron density along a striation which were compared to measured light intensity variations. It was found that there were large variations in both electron density and brightness with the brightness maximum just to the cathode side of the electron density maximum. These results are compared to the results of other investigations and some points of disagreement noted.

ISSN:0021-8979    

DOI:10.1063/1.1729700

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Mechanical property measurements on neutron‐irradiated MgO single crystals show that hardening is caused by fast neutrons exclusively. Microhardness measurements, followed by etching to reveal dislocation distribution, permit an analysis of plastic flow even on samples which are so embrittled by the irradiation (with a dose of 1019nvt) that it has not been possible to bend them. As determined from 3‐point bending experiments on samples annealed at temperatures up to 1200°C, it does require an increasingly higher stress to form a dislocation (source hardening) as well as to move it through the damaged lattice (friction hardening). The type of defects responsible for such behavior are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1729701

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Pulse‐echo ultrasonic attenuation measurements were made for longitudinal and transverse waves in the [100], [110], and [111] propagation directions in NaCl specimens cut from a single boule. The attenuation &agr; was proportional to the orientation factor &OHgr; (relating the resolved stress on the slip system of the crystal to the applied stress), and to the square of the frequencyf. Under x‐ray irradiation, &agr; decreased for modes with &OHgr;=≠0 but remained constant where &OHgr;=0. Dislocation damping is considered to cause the loss.

ISSN:0021-8979    

DOI:10.1063/1.1729702

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Esaki diodes using theAandBor opposite {111} faces of zinc‐doped gallium antimonide were fabricated using tin—tellurium spheres. Diodes made by alloying to theBface exhibit approximately an order‐of‐magnitude higher peak tunneling current density than those made by alloying to theAface. Differences are found in the junction geometries. Junctions fabricated by alloying to theBor {1¯1¯1¯} face are generally planar and delineation of these is pronounced, suggesting enhanced impurity concentration in their recrystallized regions.Aor {111} face alloyed junctions are curved and tend to be obscurely delineated. The capitance per unit area of theBdiodes was approximately twice that of theAdiodes. ThusJp/Cvalues were typically 5–7 times higher for theBdiodes. Calculations indicate, for typicalAandBdiodes, excess carrier concentrations 4.0×1018and 1.5×1019/cm3, respectively. The higher tunneling current, the higher capacitance, and enhanced delineation of the planarBjunction are apparently the effects of higher impurity concentration in the regrowth region due to the difference of the segregation coefficient of tellurium in gallium antimonide with crystallographic direction of growth.

ISSN:0021-8979    

DOI:10.1063/1.1729703

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

High‐purity zinc wires of different grain sizes were subjected to increasing tensile loading at different temperatures, and the associated changes in length, internal friction, and shear modulus were simultaneously measured. The work‐hardening coefficient was found to be parabolic and to decrease with increase of grain size and temperature. This was interpreted in terms of the associated variations of the dislocation slip distance. An internal friction peak was observed at low stresses before excessive slip took place, and was attributed to the freeing and subsequent locking of the loosely pinned dislocations under the action of the applied stress. In fine‐grained samples, a rise in the shear modulus was also observed and was attributed to the dislocations created by activated Frank—Read sources, which pile up against grain boundaries. The grain‐boundary fracture surface energy, calculated from the observed dependence of the fracture and yield stresses on grain size, amounted to 1280 ergs/cm2at room temperature.

ISSN:0021-8979    

DOI:10.1063/1.1729704

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Taylor‐type instabilities have been observed using sodium as a magnetohydrodynamic model of plasma. The wavelengths were found to be in fair agreement with the theory of Kruskal and Schwarzschild.

ISSN:0021-8979    

DOI:10.1063/1.1729705

出版商:AIP    

年代:1963

数据来源: AIP