THERMODYNAMIC PROPERTIES OF K2U4O12(S) AND K2U4O13(S) BY EMF AND CALORIMETRIC MEASUREMENTS

The coexistence of K2U4O12(s) and K2U4O13(s) in the K-U-O system up to 1200 K was established, The EMF measurements over the above phase fie ld were carried out using a calciastabilized zirconia solid electrolyt e galvanic cell in the temperature range 1053 to 1222 K. The equilibri um oxygen partial pressure above the phase fields was calculated to be lnp(O-2) kPa +/- 0.09 = -31452/T + 25.065. The enthalpy increment val ues of K2U4O12(s) and K2U4O13(s) were measured using a high temperatur e Calvet calorimeter by drop method and the thermodynamic values were suggested for the compounds. (C) 1997 Academic Press.