Different Phases of Fluorido-Tantalates

Boca/ B. Kubikova/ F. Simko/ M. Gembicky/ J. Moncol/ and K. Jomova  

The motivation of this contribution is to point out that some data on the potassium fluorido-tantalates treated up to now need to be updated, deeply analysed, new data added and some of them revised. Finally a new sight on the system can be generated. 

K2Tap7, also known as K-salt, is one of the components for the electrodeposition of pure tantalum metal. Since K2Tap7 is used for molten-salt applications, knowledge of the structural changes during heating below the melting temperature is desirable in order to propose an accurate model of solid-liquid phase transitions. 

The model of the phase transition a-K2Tap7 p-K2Tap7 proposed in Refs [6, 7] was based on knowledge derived only from X-ray powder diffraction data, IR spectroscopy and differential thermal analysis. 

Upon heating to 509 K, monoclinic a-K2Tap7 transforms to orthorhombic p-K2Tap7 [8]. The crystal structure of p-K2Tap7 is composed of discrete K+ cations and anions. In the anion, the Ta atom is 

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