The following paper deals with evidence of ferroelectricity in KNb${\mathrm{O}}_3$ and NaNb${\mathrm{O}}_3$. Temperatures at which both materials undergo crystallographic 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 KNb${\mathrm{O}}_3$.

• Received 25 January 1951

DOI:https://doi.org/10.1103/PhysRev.82.727