Absorption loss due to complex anions in fluorozirconate glasses

A fluorozirconate glass ZBL-3 with the molar composition 0.62 ZrF
4
, 0.33 BaF
2
, 0.05 LaF
3
was doped with various amounts of NaPO
3
, KHSO
4
, and also with Na
2
CO
3
, NaNO
3
and TiOF
2
. Characteristic absorption bands were observed at 2100 cm
^-1
and 1640 cm
^-1
for phosphates and 2150, 2350, and 1600 cm
^-1
for sulfates. The absorption resulting from 1 ppm of P is 900 dB/km at 2100 cm
^-1
while it is slightly lower for 1 ppm of S. Carbonates and nitrates are decomposed in the glass melt and result in a small shift of the infrared multiphonon absorption.