COLOUR CENTRES AND THERMAL BLEACHING OF SODIUM CHLORIDE AND LITHIUM FLUORIDE

Journal Article · Sun Jul 01 04:00:00 EDT 1962 · Physica

DOI:https://doi.org/10.1016/0031-8914(62)90121-0· OSTI ID:4776043

Rao, K V; Sharma, J

The thermoluminescence light output at different stages of thermal bleaching and the corresponding changes in color centers, were investigated in the case of sodium chloride and lithium fluoride crystals, colored at room temperature by x rays. In the case of colored sodium chloride, during the first stage of thermal bleaching up to about 100 deg C, the F band decreased in intensity giving thermoluminescence and also produced another bamd at 580 m mu . The band seemed to be due to aggregates of F centers and was found to be responsible for the thermoluminescence emission at temperatures above 200 deg C. The thermal bleaching of colored lithium fluoride was found to occur roughly in three stages. The thermoluminescence light output given out by the colored crystal when heated to 180 deg C was due to the partial destruction of F-, colloid- and R/sub 1/ and R/sub 2/ bands. In the region from 180 to 340 deg C the largest light output was observed and was mostly due to the bleaching of M and F centers. In the final stage of bleaching from 340 to 380 deg C, a large amount of light was given out due to destruction of the F band and colloid centers. The results of the present investigation suggest that the emission bands at 519 m mu and 416 m mu observed in the thermoluminescence of sodium chloride are due to radiative recombination of holes with the electrons trapped at F and aggregate centers, respectively. Measurements on lithium fluoride crystals indicate that four different color centers are involved in the emission process; thus the variation in the spectral composition of the emission during thermoluminescence is likely to be due to the corresponding emission bands. (auth)

• Research Organization: Indian Inst. of Tech., Kharagpur, India
• NSA Number: NSA-17-003559
• OSTI ID: 4776043
• Journal Information: Physica, Journal Name: Physica Vol. Vol: 28
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

BLEACHING
COLLOIDS
COLOR
CRYSTALS
EMISSION
LIGHT
LITHIUM FLUORIDES
LUMINESCENCE
METALS, CERAMICS, AND OTHER MATERIALS
SODIUM CHLORIDES
SPECTRAL SHIFT
STABILITY
TEMPERATURE