Abstract:
Limestone is a common sedimentary rock composed primarily of the mineral calcite (CaCO 3
).
Though it is generally used in building industry, it has found little use in the technological
industry in the form of CaCO 3
nanoparticles. Few works abound on the optical properties of
Calcium Carbonate, and they do not extensively cover the optical properties in the IR-VIS-UV
electromagnetic spectrum range. This dearth of information over the whole electromagnetic
spectrum for Calcium Carbonate makes this research pertinent. Limestone (calcium carbonate)
from Obajana, Kogi State were collected and grounded into powdery form. A portion of the
powder was then placed on substrates and annealed at various temperature ranging from 50 to
500oC while the rest served as the unannealed sample. The annealed and unannealed samples
were irradiated in the range of 300 nm to 1100 nm in UV-Vis Spectrophotometer. The results
shows that there was increase in the absorption and transmittance of radiation in the annealed
sample than in the unannealed sample. Also, their exist a slight increase in the band energy gap
with a value of 0.07 eV due to annealing, and reduction in the values of refractive index and
optical conductivity. All these improved optical properties making the annealed calcium
carbonate material useful in solar application like anti-reflection coatings for solar-thermal
devices, thermal control window coatings and heat mirror coatings in building industry.
