Study on temperature-sensitive factors relevant to thermographic features of Tb3+-doped phosphate glasses

Intensities of the 5D4 luminescence with the 5D3 level populated by GSA and ESA transitions of Tb3+ in ternary phosphate glass were measured at different temperature between 300 K and 675 K. Acquired 5D4 luminescence intensities related to GSA and ESA excitation transitions from thermally coupled 7F6 and 7F5 levels were treated to assess luminescence intensity ratios (LIR) as a function of temperature and resulting values of relative sensitivity SR. To understand origin of marked dissimilarity of SR values observed in some few Tb3+-doped hosts reported thus far an in-depth analysis of the excitation energy flow in systems under study is made. Spectra of absorption cross section and temperature dependent absorption coefficient for ESA transition were evaluated. Rates of temperature dependent cross relaxation process governing energy transfer between 5D3 and 5D4 were calculated. It was supposed that temperature-dependent absorption of colour centres in the blue region may affect adversely relative thermal sensitivity.