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No abstract

In summary, it appears overwheliningly probable that the S and R data apply not to an alloy of approximate composition Na4Pb but to some other substance or substances as yet unidentifieri, ant1 possibly of uukriowri constitution and structurcWe are grateful to the Ethyl Corporation for financial support, and to hIr. S. AT. Rlitzer aitd r h .H. Shapiro for valuable discussions.

The results of measurements on single crystals of KNbC>3 are reported. From the dielectric constant and spontaneous polarization measurements the coefficients of the first three terms of the free energy expressed as a power series in the polarization can be found. The detailed behavior of single domain crystals in the cubic and tetragonal phases is compared with Devonshire's phenomenological treatment. Agreement with predicted dielectric constant and spontaneous polarization is reasonable. The constants of KNbOa are, compared with those reported for BaTiC>3. It is found that in all cases corresponding constants are of the same order of magnitude.