Accession Number : ADA317746

Title :   Temperature Dependent Microwave Absorption in Selected Nitrates and Nitrites.

Descriptive Note : Final rept. Jan 93-Sep 95,

Corporate Author : ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD

Personal Author(s) : Cornelison, Steven G. ; Gauss, Arthur, Jr. ; Krane, J. ; Hardy, J. R.

PDF Url : ADA317746

Report Date : AUG 1996

Pagination or Media Count : 30

Abstract : Molecular dynamics studies performed at the University of Nebraska have predicted that microwave activity should be present in some ionic molecular crystals and that significant dielectric losses may occur at or near order/disorder transition temperatures. Temperature-dependent centimeter reflection studies at frequencies from 2 to 20 GHz were performed at the U.S. Army Research Laboratory (ARL) on powdered samples of potassium nitrate, potassium nitrite, sodium nitrate, and sodium nitrite. The measurements, which show significant dielectric losses in some cases, are compared to calculations based on a Debye relaxation model. Losses observed in the salts containing nitrite ions are expected to be due to the presence of permanent dipole moments that are excited to hopping modes as the temperature is raised. Losses observed in potassium nitrate are expected to be due to the development of 'induced' dipole moments as the material nears its order/disorder transition temperature of 128 deg C.

Descriptors :   *TEMPERATURE, *MICROWAVES, *ABSORPTION, *NITRATES, *NITRITES, FREQUENCY, IONS, ARMY RESEARCH, MODELS, DYNAMICS, POWDERS, DIELECTRICS, ORDER DISORDER TRANSFORMATIONS, CRYSTALS, REFLECTION, TRANSITION TEMPERATURE, SAMPLING, MOLECULAR STRUCTURE, RELAXATION, LOSSES, MOLECULAR PROPERTIES, POTASSIUM COMPOUNDS, DIPOLE MOMENTS, IONIC CRYSTALS, SODIUM NITRATES, SODIUM NITRITE.

Subject Categories : Inorganic Chemistry
      Physical Chemistry
      Radiofrequency Wave Propagation

Distribution Statement : APPROVED FOR PUBLIC RELEASE