Thermodynamic characteristics of a new phase Bi sub(12.5)Ho sub(1.5)ReO sub(24.5) by solution calorimetry

Bi sub(2.5)Ho sub(1.5)ReO sub( 24.5) phase has been prepared from Bi sub(2)O sub(3), Ho sub(2)O sub(3) and NH sub(4)ReO sub(4). X-ray measurements have showed that Bi sub(12.5)Ho sub(1.5)ReO sub(24.5) has a cubic structure (Fm3m space group). The standard formation enthalpy of Bi sub(12.5)Ho sub(1.5)ReO sub(24.5) has been determined by solution calorimetry combining solution enthalpies of Bi sub(12.5)Ho sub(1.5)ReO sub(24.5), 6.25Bi sub(2)O sub(3) + 0.75Ho sub(2)O sub(3) + 0.5Re sub(2)O sub(7) mixture in 2 M HCl and literature data. The thermodynamic stability of Re, Ho-doped bismuth oxide with respect to binary oxide mixture has been determined. It has been established that the above-mentioned mixed oxide is thermodynamically stable with respect to its decomposition into binary oxides at room temperatures.