Vol. 32, No. 6 (1983)
1983, 32 (6): 689-696. doi: 10.7498/aps.32.689
There is a disorder-order transition in the PdAu25Fe21 and PdAu24Fe21Al4 alloys at critical temperatures of 500℃ and 550℃ respectively, The ordered phase is a superstructure of Cu3Au type. The disorder-order transition of the alloys brings about a physical change from the ferromagnetic state to antiferromagnetic state, considerable decrease in susceptibility and conductivity, and a change in the sign of thermo-electromo-tive force. The experimental results show that the anomalous behaviors of the alloys result from the atomic ordering and the change of d-band states.
POSITRON ANNIHILATION STUDY OF ELECTRIC POLARIZA-TION EFFECT IN PIEZOELECTRIC CERAMICS OF PbZrO3-PbTiO3 SYSTEM
1983, 32 (6): 697-704. doi: 10.7498/aps.32.697
The electric polarization effect in piezoelectric ceramics of PbZrO3-PbTiO3 system (PZT) was examined by positron lifetime measurements. It was found that the mean lifetime τm increases with the increase of the electric field E. The micromechanism of the increase of τm was discussed, it may be mainly attributed to that the increase of the inner electric field would be energetically in favour of the positrons to form in qPs state. The measurements of the coupling factor K_p, the piezoelectric constant d33, and the dielectric constant ε33T/ε0 were also carried out and the results were compared with that of positron lifetime measurements. It is suggested that there is a possibility to take positrons as a tool for studying the extent of the domain turning and the changes of the energe situation of the electrons during the polarization.A special single sample method was used in the present work. Finally, our method of date analyzing was discussed.
DETERMINATION OF THE COMPLETE SET OF ELECTROELASTIC CONSTANTS OF FERROELECTRIC CRYSTAL (K0.20Na0.20Sr0.60Ba0.20)Nb2O6
1983, 32 (6): 705-712. doi: 10.7498/aps.32.705
This paper discusses the measuring method and the measuring program of all of the dielectric, elastic and piezoelectric constants of ferroelectric single crystal (K0.20Na0.20Sr0.60Ba0.20)Nb2O6. This crystal was first grown by the authors. All 53 date of the dielectric, elastic and piezoelectric constants and some of the electromechanical coupling factors are published for the first time. Most of these date are measured in accordance with "IRE Standards on Piezoelectric Crystals" except that elastic coefficients S66 and S13 are measured by the thickness shear mode of the (zxl) 45° specimens and the length extensional mode of the (xzt) 45° bars respectively. The measuring accuracies are also discussed.
This paper deals with the propagation of the waves (including relaxation, pressure, and density waves) and thermal mode in nonadiabatic and nonequilibrium gases. Based on the mechanism of thermal disturbance feedback, a new governing equation for the propagation of disturbances and the dispersion relation has been obtained. Some new conclusions are reached. For example, the disturbance is either purely growing or slow-damped which presents a reasonable explanation for abnormal absorptive phenomena of infrasonic sound waves in atmosphere; nonadiabatic characteristic of gas can cause a remarkable dispersion phenomena; the propagation of noise can be damped, etc. In addition, the conclusion that pressure and density waves and thermal mode may be unstable agrees with the experimental fact about, thermal instability in high power laser discharges.
1983, 32 (6): 723-729. doi: 10.7498/aps.32.723
This paper presents experimental observations and the cause for removal of laser mode degeneracy. Frequency difference between degenerate laser modes were analyzed and calculated in detail. Graphical plot of frequency difference between degenerate laser modes after removing degeneracy versus cavity detuning is given.
TRANSPORT PHENOMENA IN DENSE GASES AND VISCO-SITY,THERMAL CONDUCTIVITY FOR ARGON OF MOLECULES INTERACTING WITH A SQUARE-WELL POTENTIAL
1983, 32 (6): 730-749. doi: 10.7498/aps.32.730
In order to discuss the transport phenomena in dense gases, a generalized Enskog's equation is suggested. We notice that the correlation function Y(r) can be obtained from virial expansion of the equation of state.In this paper, formulas for calculating viscosity and thermal conductivity for dense gases of molecules interacting with a square-well potential are derived. Using these formulas, we have calculated the viscosity for argon at temperatures 173 K and 348 K and the thermal conductivity for argon at temperatures 183 K and 348 K. Comparison of theoretical results with the experimental measurements shows that the agreement is good and is better than another theoretical calculations made so far.
1983, 32 (6): 750-761. doi: 10.7498/aps.32.750
In this article, the critical behavior of birth-death equation for trimolecular reactionmodel has been discussed. If 1+k3A23D1)/D2)1/2]2, it is just the critical behaviorof the trimolecular model itself. The amplitudes of the unstable fluctuation waves have been taken as order parameters describing the change of fluctuation distribution near the critical point (B=Bm). By using the renormalization method to evade the difficulty due to the divergence of the fluctuation of steady solution at Bm, we obtain the generalized Landau-Ginzburg equations for the amplitudes of average values and fluctuation of partical numbers.The analytical and numerical analysis show that, as B increases beyond Bm, the variance also has a periodical stable part, the amplitude of which is very large and determined mainly by the saturated amplitudes of average particle numbers.
1983, 32 (6): 762-769. doi: 10.7498/aps.32.762
The problem of phase retrieval from image and diffraction patterns is of importance in electron microscopy. In this paper the true phase can be extracted uniquely and accurately by Gerchberg-Saxton iterative algorithm for the wave function, its amplitude being unity or a linear function, while its phase being a parabolic, sinuous or exponential function.A computer program for retrieving the phase has been worked out. As an image wave function is given, its Fourier transform may be calculated by the discrete fast Fourier transform algorithm. So we can recover the phase with G-S algorithm, using a random initial phase between -π and +π. The numerical examples are given in detail. The phase retrieval solution is stable under fluctuation of input initial phase up to 1 rad.
1983, 32 (6): 770-779. doi: 10.7498/aps.32.770
Based on the consideration that the effective Hamiltonian matrix determining the zero field splitting parameter a of S-state ion in cubic crystal field possesses the same property with that of spin Hamiltonian matrix, a simple relation between parameter aand the non-diagonal elemente C of the effective Hamiltonian matrix in L-S representa-tion was derived as a=2/51/2C.As an example, the value of a of Mn2+ ion in CaO crystalwas calculated by using this relation, and the result agrees well with the experimental value.
1983, 32 (6): 780-785. doi: 10.7498/aps.32.780
The phase transition properties of Nb doped PZT 95/5 type ferroelectric ceramics under the action of shock wave in "normal mode" condition have been investigated. Under the condition of parallel inductance-capacitance load, the maximum current 1360A has been obtained. Under the condition of resistance load, the maximum voltage 145×103 V was obtained. These results are in good agreement with theory.
A single-crystal X-ray diffraction analysis has been performed on LiErP4O12 Synthesized by the flux method. The crystal belongs to monoclinic system with space group C2/c, z=4, and cell parameters α=16.229?, b=7.009?, c=9.524? and β=125.92°. A full-matrix least square refinement with secondary extinction as a structure parameter gave R=0.058 for 1282 independent reflections. The basic structural units are helical ribbons, (PO3)n, formed by corner-sharing tetraheclra of PO4. The ErO8 dodecahedra are isolated from each other in the sense that they do not share any O atoms.
SYNTHESIS AND CRYSTALLIZATION OF A NEW COMPOUND K2Te4O9·3H2O IN THE TeO2-K3PO4-H2O SYSTEM UNDER HYDROTHERMAL CONDITIONS
1983, 32 (6): 791-794. doi: 10.7498/aps.32.791
We investigated preliminarilly the synthesis and crystallization in the system TeO2-K3PO4-H2O under hydrothermal conditions. It was found that in addition to the crystals of TeO2, crystals of a new phase which we called γ could be obtained in the given range of constituent and growth conditions. The γ crystal belongs to trigonal system with α= b=10.734 ?, c=21.041?, α=β=90°, γ=120°. The formula of γ is K2Te4O9·3H2O. Furthermore,it was shown that the crystallized product in the crystallization zone depends mainly on the molar ratio of starting materials k=TeO2/K3PO4 in the system. When k≤1.90, the crystallized phase only consists of γ crystals, k≥2.22, only TeO2 crystals appears, while 1.902 are present together.Finally, the DTA curve and the relative intensities and corresponding d-values of X-ray powder diffraction pattern of γ-phase are also given.
1983, 32 (6): 795-798. doi: 10.7498/aps.32.795
By determining the relations between the effective distribution coefficient of MgO in the congruent LiNbO3 and the phase-matching temperature and the concentration of MgO, chemical composition which makes the Mg :LiNbO3 to get the highest phase-matching temperature has been found. The problems frequently encountered in heavily doped Mg:LiNbO3 crystal growth, such as growth striations and precipitation etc, have been resolved.The Mg:LiNbO3 crystals with high resistance to light-induced refractive index changes and good optical quality have been grown. Using the crystals for frequency doubling of a continuously pumped acousto-optical Q-switch Nd :YAG laser, second harmonic output with the highest avarage power of 2W have been obtained.
DETERMINATION OF THE ATOMIC CONCENTRATION RATIO ON InP (100) CLEAN SURFACES BY X-RAY PHOTOELECTRON SPECTROSCOPY
1983, 32 (6): 799-802. doi: 10.7498/aps.32.799
The atomic concentration ratio of In to P on InP(100) surfaces has been determined to an accuracy of 20% by measuring the In 3d5/2 and P 2p XPS intensities and using the corresponding atomic sensitivity factor values previously derived by the authors. The experimental results show that there exists a preferential sputtering effect for the argon ion bombardment. The In to P concentration ratio reaches a value of 2.2 at 1 keV ion beam energy and increases monotonically with the ion energy. After annealing the sample at approximate 300℃ in ultra high vacuum for 30 minutes, the In to P ratio at the surface decreases to 1.2 which is quite closed to the value of bulk stoichiometric ratio. It can be deduced from the angular dependence of the XPS intensities and the chemical shift of In 3d5/2 binding energy that after the heat treatment, the In-P chemical bonds which were broken by the ion bombarding could reconnect, and the surface atomic arrangement was thus led to become an ordered structure with an outmost atomic layer rich in In.
1983, 32 (6): 803-807. doi: 10.7498/aps.32.803
XPS analyses of the GD-a-SixC1-x:H samples have been made, the results are similar to those of katayama. In this paper, the chemical shifts of Si2p and Cls levels, the observed valence-electron plasmon energy hωp and the atomic density of our samples with various alloy composition x are presented. The results are discussed preliminarily.
1983, 32 (6): 808-811. doi: 10.7498/aps.32.808
The surface of synthetic diamond have been observed employing reflection electron microscopy with both TBM and STEM instrument. It is found that there are slip steps of screw dislocations, growth steps and microcrystals on the surface. The result shows that the surface of sythetie diamonds is characteristic of crystallization from solution.
1983, 32 (6): 812-818. doi: 10.7498/aps.32.812
Fine γ-Fe2O3 particles with diameter of 80-700? were prepared. Their saturation magnetization per unit mass σs and specific surface area Sa were measured. An empirical formula σs(s) = σs(∞(1-aSa) was obtained. It was proposed that the fine particles consist of two parts: the first part is the surface layer, whose magnetic moment can not be turned entirely to the field direction by the applied magnetic field, but make an average angle (canting angle) with the field. The second is the inner part of the particles, whose magnetic moment can be aligned along the direction of the applied magnetic field. The above empirical formula can be interpreted very well by this simple model.
1983, 32 (6): 819-822. doi: 10.7498/aps.32.819
By calculating the minimum of thermodynamic potential in Landau's theory of second order phase transition, the direction of second order structural phase transition at Γ point of Ohn space groups are obtained. "Maximal subgroup" condition is discussed.
1983, 32 (6): 823-828. doi: 10.7498/aps.32.823
In this paper, the two-component Dirac equation in Schwarzschild background space time is reduced to a one component second order equation. The effective potential and the L-S coupling term are given. Near the horizon, there is a potential wall. When K2>3η2, there is another potential well by the wall. So the particle resonating in the well will be absorbed by the horizon after penetrating through the wall. With WKB approximation, the resonance spectrum and its width are obtained. For the case of Re-issner-Nordstrom background space time, the same procedure is also carried out, and the results are discussed briefly.