Synthesis, crystal-structure refinement and properties of bastnaesite-type PrF[CO₃], SmF[CO₃] and EuF[CO₃]

Abstract

By adding a hot aqueous solution containing KF and K2[CO3] to another hot aquatic brine of Pr[NO3]3 ⋅ 5 H2O, Sm[NO3]3 ⋅ 5 H2O or Eu[NO3]3 ⋅ 5 H2O with a 1.3 times excess of the anion-providing solution, amorphous water-insoluble powders of PrF[CO3], SmF[CO3] and EuF[CO3] can be obtained. Through hydrothermal treatment at 210 °C for five days crystalline powders could be synthesized and their crystal structure was refined with Rietveld methods based on PXRD data. The named compounds crystallize in the bastnaesite-type structure with a = 710.912(12) pm, c = 976.811(6) pm for the praseodymium, a = 704.77(2) pm, c = 971.83(4) pm for the samarium and a = 700.734(6) pm, c = 969.066(8) pm for the europium compound, all hexagonal with Z = 6. Upon heating them, the compounds lose CO2 and fluoride oxides REFO emerge. Thermogravimetric experiments with crystalline samples show thermal stability up to 420 °C for PrF[CO3], 400 °C for SmF[CO3] and 340 °C for EuF[CO3], but decomposition below 200 °C for the amorphous ones. Infrared spectroscopy confirms only marginal portions of [OH]− instead of F− anions in all cases. The RE 3+ cations are coordinated by 9 + 2 anions at distances between 236 and 254 pm plus 326 pm to F− anions and oxygen atoms bonded to carbon as oxocarbonate anions [CO3]2−. Triggered by ultraviolet radiation, the bulk sample of EuF[CO3] shows a poor red luminescence.

‘Young crystallographers’ rejuvenate crystallography in Germany

“…Finally, possibly our biggest project so far was our special issue, which appeared in 2022 in the journal Zeitschrift fu ¨r Kristallographie. This issue featured contributions from young crystallographers from all over Germany on a wide variety of topics, including Theory (Subramaniam et al, 2022;Ernst et al, 2022;Nentwich et al, 2022b;Hornfeck, 2022;Wiedemann, 2022), Crystal Growth (van Terwingen et al, 2022;Weigel et al, 2022, Buyer et al, 2022, Structure Solution (Heinen et al, 2022;Folkers et al, 2022;Heidecker et al, 2022), and Properties (Ludt & Zschornak, 2022;Breternitz, 2022).…”