Prepd by thermal decompn of (NH4)2ZrF6: v. Hevesy, Dullenkamp, Z. Anorg. Allg. Chem. 221, 161 (1934); according to the equation ZrCl4 + 4HF → ZrF4 + 4HCl: Wolter, Chem. Ztg. 51, 607 (1908); from zirconium oxide and fluorine: Haendler et al., J. Am. Chem. Soc. 76, 2177 (1954).