In this article we present results of optical and ESR studies that have allowed us to study the behavior of Cr'+ at disordered low-field sites within a mullite ceramic host. The results indicate that the existence of these low-field ions, which are likely at sites in regions of disorder, accounts for most of the spectroscopic anomalies previously noted in these materials. Furthermore, energy transfer from ordered high-field to disordered low-field ions is observed. The resulting complex spectra are deconvoluted by means of the recently developed technique of saturation-resolved fluorescence spectroscopy.

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In this paper we show that the luminescence lifetime of CP § doped solids is a function of the degree of mixing of the 2E and 4T2 states. This mixing, due to the spin-orbit interaction, is a function of the energy separation, h, of the 4T2 and 2E levels, and consequently the crystal field parameters. This derivation is experimentally verified by applying hydrostatic pressure and tensile stress to crystalline hosts. The subsequent changes in h markedly affect the lifetime. This result is then applied to amorphous solids which exhibit site dependent lifetimes, such as the CP § :mullite-ceramics.Extensive spectroscopic studies have been carried out on Cr 3 § doped systems in past decades. The Cr 3 § ion is found to occupy only sites of octahedral symmetry, although the degree and type of distortion varies from host to host, and the energy level structure is well known. In recent years attention has been directed toward Cr 3 § in glass and glass-ceramic hosts. The possible commercial application of these materials makes them particularly interesting. In these systems a large degree of inhomogeneous broadening is observed and many of the luminescent properties are found to be strongly dependent on the energy level separation, h, of the 4T 2 and 2E levels (1, 2).The 4T2 -4A 2 splitting is very sensitive to the crystal field strength Dq while the 2E-4T2 splitting is not. Consequently, the energy level separation h is also a function of Dq (varying linearly, to first order, with Dq). For high-field

We present a saturation-based technique designed to isolate and uncouple individual components of inhomogeneously broadened spectra that are simultaneously coupled to each other through spectral overlap and energy-transfer interactions. We have termed the technique saturation-resolvedfluorescence spectroscopy; we demonstrate its usefulness in deconvoluting the complex spectra of Cr'+:mullite glass ceramic.