摘要:

Measurements of the temperature dependence of the conductivity of single crystals of ammonium dihydrogen phosphate are described. Impurities introduced in known amounts as substituents in the lattice enable the activation energy for mobility to be separated from the total energy in the Boltzmann factor for conduction. With Ba++as impurity, the activation energy is 10.1 kcal/mole, with SO4−−10.9; the average, 10.5 kcal/mole, is taken to be the activation energy for mobility in this crystal. It ls proposed that activation for mobility in this solid is due to the simultaneous breaking of two hydrogen bonds independently. The &sgr;0factors, both for intrinsic conduction and for impurity conduction, agree reasonably well with the values expected from the theory of ionic conduction. Measurements on crystals enclosed in an evacuated space show that hydrogen gas is generated by the electrolysis of the crystal. According to Faraday's law the theoretical yield for a univalent ion leading to a diatomic molecule (H2) as product is 0.5 mole/F; the observed yields ranged from 0.3 to 0.7 moles/F. It is inferred that the conduction is ionic and that the migrating particle is probably the proton. From the conduction data for the pure crystal, the energy required for the formation of ions within the crystal is calculated to be 19.8 kcal/mole. The mobility process in this crystal shows a strong resemblance to that in ice. Both appear to be referable to the breaking of two hydrogen bonds simultaneously and to the tunneling of protons between equivalent sites. Both crystals have hydrogen bonds as an important part of their structure.

ISSN:0021-8979    

DOI:10.1063/1.1713809

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The systematic errors inherent in the numerical evaluation of the various moments of an experimental paramagnetic resonance line are discussed as a function of the choice of the shapes and the arbitrary cutoff of wing contributions. Lorentzian and Gaussian first derivative shapes are used as models. Expressions for the zeroth, second, and fourth moments of these shapes are derived in generalized coordinates with an arbitrary cutoff. The generalized coordinates, which contain parameters related to easily measured experimental quantities, permit application of the results to any line of the Lorentzian or Gaussian shape.

ISSN:0021-8979    

DOI:10.1063/1.1713810

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

An experimental determination of the drift velocity of low‐energy electrons in argon, nitrogen, carbon dioxide, several mixtures of argon and nitrogen, and several mixtures of argon and carbon dioxide used a pulsed ionization chamber with alpha particles as the source of ionization. The experimental data for the single gases serve to verify the experimental technique. The results and a detailed estimation of the possible experimental errors are presented.

ISSN:0021-8979    

DOI:10.1063/1.1713811

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The locations of domains appearing on the surface of a BaTiO3crystal have been observed by repeated partial switching and etching to determine how frequently the domains appear at the same location on successive applied pulses. The ratio of the number of repeating locations to that of all locations is (10±1.6) % for a series of six pulses at 20 kV/cm on crystals with a positive internal bias and (28±5) % on crystals with a negative bias. The simplest interpretation of the results is that new domains can nucleate at points in the crystal remote from imperfections. This interpretation is in rough agreement with Landauer's calculation of the probability of thermally activated new domains for a 180° wall energy of 0.4 erg/cm2.

ISSN:0021-8979    

DOI:10.1063/1.1713812

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The shifts of the (111) and (200) x‐ray diffraction lines have been measured by both the centroid and the peak method. From these measurements the stacking fault probability &agr; and the twinning fault probability &bgr; can be obtained on powdered samples prepared by filing. These results show a parabolic type of dependence of &agr; with composition, whereas the stacking fault probability &agr; obtained from previous measurements using the same technique on Cu‐Zn and Ag‐Cd alloys had a linear dependence with composition.By means of a simple argument the relative stacking fault energies for these alloys can be deduced and compared with those obtained on similar Cu‐Ge alloys by Howie using thin‐film electron microscopy and by Haasen and King using tensile tests.

ISSN:0021-8979    

DOI:10.1063/1.1713813

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The temperature dependence of ferromagnetic resonance losses was measured for single‐crystal samples of lithium ferrite and yttrium iron garnet that were treated to increase or decrease the state of order of the atomic structure. The maximum linewidth, at low temperatures and caused by residual impurity ions, is much greater for the more ordered state as contrasted to the more disordered state. An explanation of these observations is given in terms of expected changes in the energy levels of the impurity ions with changes in the state of order.

ISSN:0021-8979    

DOI:10.1063/1.1713814

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The recently developed method of etching fission fragment tracks in mica appears to be applicable to the measurement of neutron exposures in irradiation tests. The sensitivity of the method depends on the concentration of fissile elements. The naturally occurring uranium which is present in trace quantity can be used to measure thermal neutron exposures of 1016to 1021neutrons/cm2. Deposition of fissionable material on the mica would increase the sensitivity to permit measurement of 106to 1011neutrons/cm2. Density counts are reproducible to approximately 5% by using simple laboratory techniques.

ISSN:0021-8979    

DOI:10.1063/1.1713815

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The ordinary‐ray index of refraction at 5893 Å in BaTiO3was measured in the range 20°–160°C by a refined Chaulnes' method with an average error of 0.35%. Two BaTiO3crystals were studied and the results indicate a constant index of 2.368 from 20° to 105°C; above the Curie point the ordinary index increased by 1.3% to 2.398 and remained constant to 160°C.

ISSN:0021-8979    

DOI:10.1063/1.1713816

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

Hysteresis loop measurements were conducted on several commercial iron‐nickel alloys during neutron irradiations at 90°K and at temperatures up to 175°C, in both zero and saturating magnetic fields. Isochronal annealing tests were also performed on the alloys after irradiation. The low‐temperature irradiation results indicated that magnetic properties are affected not by the point defects themselves but by their motion and eventual disposition. The radiation‐induced changes appeared similar in many ways to those observed in these alloys upon magnetic annealing.Experiments on the alloys at temperatures from 70° to 175°C in a saturating magnetic field showed that the activation energy of the radiation‐induced process was 0.3 eV. In all cases the radiation‐induced changes were annealed out at temperatures below the usual ordering temperature for Ni3Fe. This recovery process appeared to be dependent upon the state of the magnetization of the sample.

ISSN:0021-8979    

DOI:10.1063/1.1713817

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

Ultrasonic propagation in Al2O3at low temperatures and high frequencies (to 3000 Mc/sec) is discussed in terms of the relations given by Woodruff and Ehrenreich. Phonon relaxation times calculated from thermal conductivity measurements are used. The measured low‐temperature attenuation values at 1315 Mc/sec agree with the calculated values. A comparison of attenuation as a function of frequency is made among Al2O3, Ge, Si, and quartz. On comparing experimental values of attenuation for pure Al2O3and impure Al2O3(ruby) it is found that impurities lead to an increase in the attenuation as would be predicted from the corresponding effect of impurities on the thermal phonon relaxation time.

ISSN:0021-8979    

DOI:10.1063/1.1713818

出版商:AIP    

年代:1964

数据来源: AIP