Iron 2 nitrate nonahydrate

Firstly, urea coprecipitation method was adopted to fabricate nanocrystalline ZnNd_xFe_2−xO₄ (x = 0, 0.01, 0.03, 0.05) ferrites according to a previous publication with a moderate modification [34 (link)]. Analytical grade zinc nitrate tetrahydrate [Zn(NO₃)₂·4H₂O, 98% pure, Sigma-Aldrich, Darmstadt, Germany], iron(II) nitrate nonahydrate [Fe(NO₃)₃·9H₂O, 99.9% pure, Sigma-Aldrich], and neodymium(III) nitrate hexahydrate (Nd(NO₃)₃·6H₂O, 99.9% pure, Sigma-Aldrich) were used as oxidizer and urea (CH₄N₂O, >99% pure, Sigma-Aldrich) was used as a fuel additive. A number of proper ions: Zn²⁺ (1 mmol) combined with Fe³⁺ [(2−x) mol] and Nd³⁺ (x mol) (x = 0, 0.01, 0.03, 0.05) were dissolved in distilled water. The final pH of the solution was adjusted at 5.0, and then was heated to 100 °C for 1 h. The precipitation was collected, washed with distilled water (3 × 20 mL) to eliminate metal ion and anion traces and then calcinated up to 500 °C for 2 h (ramping rate of 10 °C/min). The product was ground and stored at a vacuum container.