Fluoride glasses: fluorozirconates

The Judd-Ofelt parameterization accounts fairly well for the properties of Nd3+ in fluoride glasses, although the calculated radiative lifetime of the 4F3/2 level is quite systematically overestimated, as compared to the experiment. For instance, for fluorozirconate glasses, the experimental lifetime is in the 400-450 ps range, to be compared with 450-500 ps for the calculated one [36]. 

Nd3+ ions are by far the most widely investigated ions in all types of materials, essentially because of the ideal, 4-level, 1.06 m laser transition from 4F3/2 to 4In/2 shown in Fig. 5. Thus, the spectroscopic properties of Nd3+ ions are reported for a large number of different compositions of fluorozirconate, fluoroindate, fluorohafnate, fluoroaluminate and other kinds of fluoride glasses [31,36,63-69]. 

Gd3+ ion possesses high energy levels located in the UV. Absorption spectra of Gd3+-doped fluoride glasses show several peaks in the 240-320 nm range. They correspond to transitions from the 8S7/2 ground state to the 6P, 6I, and 6D excited states. Judd-Ofelt parameters and experimental lifetimes have been determined for Gd3+-doped fluorozirconate [34,141], and fluoroindate glasses [142], X-ray excitation of both glasses leads to radiative emission from all excited states 6P, 6I,... 

All fluoride glasses have excellent optical properties and transmit more than 50% between 0.25 pm and 7pm. While fluoroaluminate glasses do not transmit as far as fluorozirconate glasses, non-ZrF4 based on heavy metal can transmit to even longer wavelengths. As a result, fluoride glasses are candidate materials for both bulk windows and fibers for the IR. 

Fluoride glasses have been known since 1926, when it was discovered that beryllium fluoride could be cooled below the liquidus temperature without crystallization. Little further development took place until 1974, when Poulain et al. made the first synthesis of ZrF4-NaF-BaF2-NdF3 [1]. During the past three decades, much attention has been paid to the family of fluoride glasses [2], especially fluorozirconates such as ZBLAN... 

Qe parameter. For Dy -doped glasses, they found that the Q2 value showed the order sulfide > tellurite > fluorozirconate > fluoroindate. For the 2(, parameter, this order is reversed. However, Tanabe et al. (1995b) found no correlation between the parameter and the isomer shift in fluoride glasses. This is probably due to the small covalency in fluoride glasses (low 6s electron density). 

Dejneka M., Snitzer E., Riman R.E. Spectroscopic characterization of Eu " "-doped inorganic and alkoxide sol-gel derived fluorozirconate glass and zirconium fluoride gels. J. Non-Cryst. Solids... 

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