Abstract
Previous work has revealed the existence of high field site (HFS) Cr3+ ions in the mullite glass ceramics which relax through R-line emission from the excited 2E state. Recent studies of the anomalous spectral behavior of this material have suggested the existence of CR3+ ions at disordered low field sites (LFS) which emit broadband 4T2 emission at longer wavelengths. In this paper we report the results of excitation spectra monitored at the R-line or broadband 4T2 emission wavelengths which have allowed us to determine the site distribution. These measurements show that the maxima of the HFS 4T1 and 4T2 absorption bands lie ~1000 cm−1 higher in energy and have a bandwidth ~1500 cm−1 narrower than the overall absorption bands of the entire site distribution. From these data we conclude that ~10% of the ions are still in LFS in the mullite glass ceramic sample after heat treatment; radiative energy transfer exists from HFS to LFS ions resulting from the absorption of HFS R-line emission of LFS ions; the Dq value of the HFS ions increases with the degree of heat treatment. Lifetime measurements reveal a site dependence of the luminescence decay. The lifetime of the HFS R-line emission varies from 6.5 to 1.5 ms as the excitation wavelength is scanned from 532 to 670 nm, and the lifetime of the LFS 4T2 emission varies from 280 to 50 μs as the excitation wavelength is scanned from 563 to 743 nm.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call