ABSTRACTS OF TECHNICAL ARTICLES 211 



The relative amounts of electron emission from the cathode in a Townsend 

 discharge caused by ions, photons, and metastables have been studied experi- 

 mentally for several cathodes in argon, using pulsed-light stimulation of the 

 discharge. The current initiated by metastables exhibits a slow build-up and 

 deca}', thus permitting easy separation fi-om the faster rising effects of gas 

 ionization and electron emission by photons and ions. Time constant studies of 

 the slow component yielded a diffusion constant for metastable argon atoms of 

 45 cm^ sec~i at one millimeter pressure. The efficiencies of electron emission by 

 metastables and ions was found to be closely the same, while the quantum 

 yield for photon emission was found to be generally smaller. 



Electrical Properties of aFe-yOz and aFe-yOz Containing Titanium.* F. J. 

 MoRiN^ Phys. Rev., 83, pp. 1005-1010, Sept. 1, 1951. 



Electrical conductivity. Hall effect, and Seebeck effect have been measured 

 on two sets of polycrystalline samples of aFe203 and aFe203 containing from 

 0.05 to 1.0 atomic per cent titanium (n-t3^pe impurity). One set of samples con- 

 tained 0.6 atomic per cent excess of iron (n-type impurity), the second set con- 

 tained 0.6 atomic per cent deficienc}' of iron (p-type impurity). 



The conductivity of pure aFeoOs is independent of this amount of stoichio- 

 metric deviation. The slope of the log conductivity vs reciprocal temperature 

 plot is 1.17 ev and the intercept at 1/T -= is 2.1 X 10* ohm-i cm-i. Room 

 temperature conductivity varies from — lO"^"* ohm"' cm~i (extrapolated) for 

 pure aFe203 to 0.3 ohm~i cm"' for aFe203 containing 1.0 atomic per cent 

 titanium. 



The measured Hall ^'oltages seem to result entirely from magnetization of 

 the samples, which are weakly ferromagnetic, and disappear above the ferro- 

 magnetic Curie temperature. 



The temperature variations of the Fermi level are determined from Seebeck 

 data. The temperature variations of carrier concentration are determined from 

 Fermi level and of mobility from carrier concentration and conductivity for 

 some samples. Carrier concentration results indicate that each added titanium 

 ion donates approximately one electron to the conduction process. jNIobilities 

 are found to be less than 2.0 cmVvolt sec, suggesting that conduction involves 

 electrons in the d level of iron. 



Acceptance Inspection of Purchased Material.* J. E. Palmer' and E. 

 G. D. PatersonK Ind. Quality Control, 8, pp. 15-19, Sept., 1951. 



This paper describes some of the principles and procedures employed in the 

 inspection of purchased material in the form of components or finished products. 

 The authors' experience has been largely with procedures used in the Bell Sys- 

 tem, and the illustrations have therefore been drawn from this source. It is felt, 

 however, that considerations leading to the choice of specific inspection tech- 



* A reprint of this article may be obtained on request. 

 1 Bell Tel. Labs. 

 3 W. E. Co. 



