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Samples of LaSrNiO4 were synthesised from La2O3, NiO, Sr(NO3)2 in concentrated nitric acid and investigated by solution calorimetry. Using the present data on the dissolution enthalpy of La2O3, NiO, SrCO3 and some literature data, the thermodynamic values of the reaction of LaSrNiO4 formation from: (1) La2O3, SrO, NiO; (2) La2O3, NiO, SrCO3; (3) La(OH)3, Sr(OH)2, Ni(OH)2; (4) and from La2O3, NiO, Sr(NO3)2 were calculated. The calculated values permitted to conclude that LaSrNiO4 reacted with CO2 giving a mixture of La2O3, NiO, SrCO3 and with H2O forming metal hydroxides. The formation of LaSrNiO4 from simple oxides is thermodynamically favourable. The dependence of formation enthalpies on the atomic number of transition metals (Cu, Co, Ni) was analysed. The temperatures at which reactions of LaSrNiO4 formation from La2O3, NiO, SrCO3 and from La2O3, NiO, Sr(NO3)2 became thermodynamically possible are 1918 K and 1172 K, respectively. This allows a conclusion to be made that La2O3, NiO, Sr(NO3)2 are preferable as starting reagents for the synthesis of LaSrNiO4. |
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