Vacuum-Thermal Syntehsis of Metaniobates and Metatantalates of Alkali Metals

摘要

Metaniobates and metatantalates of the alkali metals were synthesized by sintering lithium, sodium, potassium, rubidium, and cesium carbonates with niobium and tantalum pentoxides in the temperature interval from 650 to 850 C for 1 to 3.5 hr., at a residual pressure of 1 mm Hg. The charge, ground to 200 mesh, and with a molecular ratio of 1 to 1, weighed 20 gr. Experiments were carried out in parallel in an electric vacuum furnace and in air in a muffle furnace. The degree of completion of the reaction was determined by weight loss and from chemical and x-ray phase analyses. The content of niobium and tantalum pentoxides was determined by the weight method. X-ray analysis shows that the intensity of the lines belonging to the starting components falls with an increase in the temperature and the holding time. In products synthesized in vacuum, the lines disappear completely. It follows that the degree of completion of the reaction is higher in vacuum than in air. It is recommended that the synthesis be carried out at a temperature below the melting temperature of both the starting and final compounds. The yield of product did not differ by more than 2 percent from the theoretical.