Centimeter-wave reflection in the nitrates and nitrites of sodium and potassium: Experiment and theory

Temperature-dependent centimeter-wave reflection is studied in powdered samples of potassium nitrate (KNO₃), potassium nitrite (KNO₂), sodium nitrate (NaNO₃), and sodium nitrite (NaNO₂). Temperature-dependent reflection measurements at centimeter-wave frequencies were performed on an HP8510B Network analyzer based reflectometer. These measurements are compared to calculations utilizing a Debye relaxation model. Reflection losses seen in KNO₂ and NaNO₂ are expected to be due to the presence of permanent dipoles that are excited to “hopping’’ modes as the temperature is raised. Although NaNO₃ shows little reflection losses, KNO₃ shows significant losses as the temperature is raised toward the order/disorder transition temperature of 128 °C. This is believed to be due to the development of “induced’’ dipole moments as the lattice becomes increasingly disordered.