Refractive Index Measurements in Fused NaNO(3) and KNO(3) by a Modified Thermooptic Technique

Area of Science:

• Physical Chemistry
• Materials Science
• Optics

Background:

• Understanding the optical properties of molten salts is crucial for various high-temperature applications.
• The temperature dependence of refractive index and polarizability in molten alkali nitrates requires precise measurement techniques.

Purpose of the Study:

• To adapt and apply a thermooptic technique for precise measurement of molten salt optical properties.
• To investigate the temperature dependence of the refractive index and polarizability of molten sodium nitrate (NaNO3) and potassium nitrate (KNO3).

Main Methods:

• Modified a thermooptic technique to study liquids.
• Measured refractive index for molten NaNO3 and KNO3 across a temperature range of 80 K above melting point.
• Utilized five different wavelengths in the visible spectrum.

Main Results:

• Observed a significant temperature dependence in the polarizability of molten NaNO3 and KNO3.
• Calculations based on the Lorentz-Lorenz formula indicated this dependence.
• The observed effect was larger than could be attributed to experimental inaccuracies.

Conclusions:

• The thermooptic technique provides reliable data for molten salt optical properties.
• The temperature dependence of polarizability in molten NaNO3 and KNO3 is a real phenomenon.
• Further theoretical investigation is needed to explain the observed polarizability behavior.