ON THE DIELECTRIC LOSS AND THERMAL BLEACHING OF CALCITE IRRADIATED BY X- RAYS

Journal Article · Tue Aug 01 04:00:00 EDT 1961 · Phys. and Chem. Solids

DOI:https://doi.org/10.1016/0022-3697(61)90005-1· OSTI ID:4842877

Rao, K V

The changes produced by x irradiation in the dielectric and optical properties of calcite crystals are reported. At ordinary temperatures, the dielectric constant as well as the dielectric loss of the uncolored crystal remains practically unchanged in the frequency region of 10 kc/s-15 Mc/s. It was found that the temperature variation of its dielectric loss is represented by an equation tan sigma = A + Be/sup -0.//sup 4kT/ where A and B are constants; this is attributed to the movement of vacancies in the crystal. On irradiation by x rays, calcite exhibits pronounced optical absorption in the ultraviolet region beyond 400 m mu ; the dielectric loss of calcite also increases considerably on coloration. The thermoluminescence shows a very strong glow peak at 85 deg C with minor ones at higher temperatures. During thermal bleaching, the dielectric loss of the colored crystal shows a prominent maximum at 70 to 120 deg C and beyond 230 deg C, it varies in the same way as in the case of the uncolored crystal. The correspondence between the change in dielectric loss and the first glow peak is possibly due to thermal release of trapped electrons. The optical absorption disappears when the crystal is heated to 350 deg C and on cooling to room temperature, its dielectric loss returns to its original value before coloration. (auth)

• Research Organization: Indian Inst. of Tech., Kharagpur, India
• NSA Number: NSA-15-029255
• OSTI ID: 4842877
• Journal Information: Phys. and Chem. Solids, Journal Name: Phys. and Chem. Solids Vol. Vol: 20
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ABSORPTION
BLEACHING
CALCITE
CALCIUM CARBONATES
CHEMISTRY
COLOR
CRYSTALS
DIELECTRICS
ELECTRONS
HEATING
IRRADIATION
LOSSES
MINERALS
THERMOLUMINESCENCE
ULTRAVIOLET RADIATION
X RADIATION