RE_2O_3-NH_4HF_2系合成稀土氟化物的反应规律

Principles of reactions in the synthesis of rare earth fluorides in RE_2O_3-NH_4HF_2 systems

在RE2O3-NH4HF2系中,以稀土氧化物和氟化氢铵为原料,分别在常压和真空状态下,研究了该体系的各步反应,提出了新的合成REF3反应规律.粉状La2O3,Gd2O3与NH4HF2在低温下开始反应,产物为RENH4F4(RE=La,Gd),NH4F,NH3和H2O,高温下RENH4F4分解为REF3和NH4F,伴有NH4F的挥发和分解;整个过程包括合成、分解和脱铵三个步骤;真空可以降低反应的起止温度.制备稀土氟化物应采用“常压低温合成-真空高温分解、脱铵”工艺.

Rare earth fluorides were synthesized with RE2O3 and NH4HF2 under atmospheric pressure and vacuum in RE2O3-NH4HF2 systems, the reactions in the systems were studied, and a new mechanism for the synthesis of REF3 was proposed. Powder La2O3, Gd203 started to react with NH4HF2 at low temperature, and the products were RENH4F4（RE = La, Gd）, NH4F, NH3 and H2O. RENH4F4 was decomposed to REF3 and NH4F at high temperature, accompanied with the volatilization and decomposition of NH4F. The whole process could be divided into three steps of synthesis, decomposition and deammoniation. The initial and final temperatures of the reactions were reduced under vacuum. The combination process of synthesis under atmospheric pressure at low temperature and decomposition and deammoniation under vacuum at high temperature should be applied to the preparation of rare earth fluorides.