1250 THE BELL SYSTEM TECHNICAL JOURNAL, OCTOBER 1951 



Abstract — ^The phase system BaO-NiO has been studied largely by means 

 of X-ray diffraction. The two compounds NiO BaO and NiO 3BaO occur in 

 the system. Their preparation and properties are described. NiO BaO is 

 black, stable in air, orthorhombic, and melts at 1240°. NiO 3BaO is gray- 

 green, unstable in air, hexagonal, and melts at 1160°. A eutectic melting at 

 1080° is observed between these compounds, but none between NiO 3BaO 

 and BaO. Intersolubility of all solid phases in the system is small, even at 

 high temperatures, but quantitative data have not been obtained. 



A Phenomenological Derivation of the First- and Second-Order Magneto- 

 striction and Morphic Effects for a Nickel Crystal* W. P. Mason^ References. 

 Phys. Rev., v. 82, pp. 715-723, June 1, 1951. 



Abstract — In order to account for experimental results which showed 

 that the saturation elastic constants of a single nickel crystal varied with 

 the direction of magnetization, a phenomenological investigation has been 

 made of the stress, strain, and magnetic relations for single nickel crystals. 

 The variation in elastic constants is shown to be a "morphic" effect caused 

 by the change in the crystal symmetry due to the magnetostriction effect. 

 In the energy equation this effect is represented by additional terms which 

 involve squares and products of both the magnetic intensities and stresses. 

 These terms are as large as the magnetostrictive terms when the stresses are 

 of the order of 10^^ dynes/cm^ The energy equation has been used to derive 

 the first- and second-order magnetostrictive effect, and the resulting terms 

 agree with Becker and Boring's empirical constants for saturation conditions. 

 For smaller magnetic intensities the terms divide up into first- and second- 

 order terms which vary differently with magnetic field intensity. It is shown 

 that the morphic effects involve six measurable constants, and some of these 

 are evaluated experimentally. 



Dielectric Properties of Sodium and Potassium Niobates/^ B. T. Matthia.s^ 

 and J. P. Remeika^ Phys. Rev., v. 82, pp. 727-729, June 1, 1951. 



Abstract — The following paper deals with evidence of ferroelectricity in 

 KNbOa and NaNbOa. Temperatures at which both materials undergo crys- 

 tallographic changes and corresponding changes in dielectric constant and 

 loss tangent are reported. Photographs of dielectric hysteresis loops and 

 values of saturation polarization taken at various points over a temperature 

 range are given for KNbOa. 



Ferroelectricity. B. T. MATTHIAS^ Bibliography. Science, v. 113, pp. 591- 

 596, May 25, 1951. 



Abstract — Under the name of Ferroelectrics one classifies those materials 

 which exhibit dielectric anomalies phenomenologically similar to the mag- 



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

 Bell Tel. Labs. 



