Synthesis and Optical Spectroscopy of MnO₄^2--Doped Crystals of Cs₂CrO₄, SrCrO₄, CsBr, and CsI

Abstract

The first low-temperature absorption and luminescence spectra of MnO4 2--doped crystals of Cs2CrO4, SrCrO4, CsBr, and CsI are reported. Single crystals of Cs2CrO4:MnO4 2-, which crystallize in the orthorhombic β-K2SO4 structure, were grown from basic aqueous solutions. An alkali−chloride flux composition was used to obtain single crystals of SrCrO4:MnO4 2- with the monoclinic monazite structure. Crystals of CsBr:MnO4 2- and CsI:MnO4 2- were prepared by slowly cooling the melt. The site symmetry in SrCrO4 is C 1, but the deviations from D 2 symmetry are small, and the spectra are analyzed in the approximate D 2 symmetry. The 2E ↔ 2T2 ligand-field transitions are strongly c polarized, and in absorption only the transition to the lowest-energy component of the split 2T2 state is observed with its origin at 10 303 cm-1. Luminescence is exclusively observed to the lower-energy component of the 2E state. By a combination of absorption and luminescence data, it is shown that, in the cubic CsBr and CsI lattices, MnO4 2- is partly incorporated in the form of Cs2MnO4 crystallites. The observed nonexponential luminescence decay for these systems indicates the existence of several manganese(VI) species with different relaxation times. Within isomorphous host lattices, a correlation is established between the temperature-quenching behavior and the size of the M6+ host ion: the efficiency of multiphonon relaxation processes increases with increasing ionic radius of M6+.

Optical properties of 3d transition metal ion-doped sodium borosilicate glass

“…The 3d 3 Mn 4+ ion exhibits absorption bands at 490 nm and 400 nm due to transitions from the 4 A 2 ground state to the 4 T 2 , 4 T 1 states, respectively. In addition, there are various oxo-anions of Mn(V) [77], Mn(VI) [78] and Mn(VII) [79] for which the optical spectra have been documented. Fig.…”

Low-temperature flux growth of sulfates, molybdates, and tungstates of Ca, Sr, and Ba and investigation of doping with Mn 6+

“…Nevertheless, no significant doping was found in our molybdates and tungstates. Not even in a chromate, with its Cr 6+ crystal radius being similar to that of Mn 6+ , could significant doping be observed [17]. In contrast, BaSO 4 and BaSeO 4 exhibit efficient incorporation.…”

“…The derived dependence ofL on C solute was similar for all the compounds. Here, BaMoO 4 is chosen as an example, because the possibility of incorporating Mn 6+ into BaMoO 4 was previously demonstrated [17]. The curve is characterized by the presence of a maximum (see Fig.…”

“…The Mn 6+ ion is a promising activator ion for future tunable lasers [12,13] and broadband fluorescent light sources [14] for applications in interferometry [15,16]. It can be incorporated into a number of hosts with tetrahedral oxo-coordination, such as sulfates, selenates, chromates, and molybdates [17], at the tetrahedral X 6+ sites where no charge compensation is required. However, Mn 6+ tends to be reduced to Mn 5+ at temperatures above ∼ 600 • C [18].…”

Synthesis of SrCrO4 nanostructures by onion inner-coat template and their optical properties

“…Strontium chromate (SrCrO 4 ) is of importance owing to its important optical behaviour, structural properties and potential applications. Especially, Zou et al recently developed MCrO 4 (M = Ba, Sr) catalyst, which may have promising application in the photocatalyst (Schenker et al 1998;Yin et al 2003). Up to now, considerable efforts have been focussed on the properties of SrCrO 4 .…”