Development of a YF3:ThF4 membrane for the possibility of determining fluoride

Abstract

Preparation of yttrium substituted thorium fluoride (YTF) solid solution, YxTh1−xF4−x (x = 0 – 0.15) by fluorinating a stoichiometric ratio of yttria (Y2O3) and thoria (ThO2) with ammonium hydrogen difluoride (NH4HF2) was acheived. The maximum solubility of YF3 in ThF4 was observed to be 15 mol %. All three compositions of YxTh1−xF4−x (x = 0 – 0.15) solid solution showed an enhanced ionic conductivity over ThF4. 5 mol % yttrium substituted ThF4 (5-YTF) had the highest ionic conductivity, almost 2 orders higher than ThF4. The F− ion selective electrode was designed and tested for estimation of fluoride ion in solution (10−1M to 10−5 M). 5-YTF had the highest sensitivity of 40.0 ± 4 mV/decade in the linear range of 10−1 M to 10−4 M. All the three sensors compositions 5, 10 and 15-YTF have sub Nerstian behavior which is attributed to strong OH− ion interefenece.The results were compared with commercial fluoride ISE (Eu: LaF3).