The current-voltage characteristics of semiconducting BaTiO3 ceramic have been investigated with electric fields up to 2×104 V/cm. The results obtained are in agreement with Heywang's model for conduction in this material (other published models being unsatisfactory) provided that allowance is made for the Ohmic drop in the bulk material. It is found that most of the current is channeled through small pores (0.1–0.5 μ diam) in the intergranular boundaries.

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We report here what we believe is conclusive evidence that the excessive degradation of critical current which occurs in solenoids wound from heattreated Nb-25% Zr wire is due to the simultaneous presence of transport current and flux jumping. Previous unpublished work in our Laboratories had shown that, while the critical current in a 5-cm short sample of Nb-25% Zr wire heated to 70boc for one hour was about 150 A in a transverse field of 20 kG, the same wire wound into solenoids went normal when producing 5 to 10 kG at critical currents less than 10 A. This same type of degradation, in a less severe form, is of course well known for solenoids wound from heavily cold-worked wire.The present experiments were performed with insulated 0.025-cm diam Nb-25% Zr wire which had been heat-treated at 700°C for one hour after the final cold-worked reduction. It has been previously reported that heat treatment of Nb-Zr alloys increases the critical current density of short samples. 2 -4 The short sample critical current vs field for this wire is listed in Table I. The wire was wound into a solenoid of approximate dimensions: 0.3-cm i. d., 1.3-cm o. d., 2.5 cm long (calculated G/ A = 434). The solenoid was cooled to 4.2°K, and a uniform magnetic field was applied to its axis. As this external field was increased smoothly from zero, with no transport current (I = 0) in the solenoid, a sequence of very narrow «1 msec CONTENT ANALYSIS

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Nuclear magnetic double resonance has been used to investigate first-order electric quadrupole interactions of Na 23 and CI 35 nuclei near an Ag ion substituted for Na in NaCI. The study has determined the direction of the principal axes, asymmetry parameter rj, and strength of the interaction e 2 Qq for sodium ions at a (2, 0, 0) position, and chlorine ions at (2, 1, 0) position relative to the impurity at (0, 0, 0).