HEAT-CAPACITY AND THERMODYNAMIC PROPERTIES OF LAFEO3 AND LACOO3 FROM T = 13 K TO T = 1000 K

The heat capacities of LaFeO3 and LaCoO3 have been determined by adiab atic calorimetry from T = (13 to 900) K, and from T = (13 to 1000) K, respectively. Both compounds undergo electronic transitions; LaFeO, a magnetic order-disorder (AF to para) transition at T approximate to 73 5 K; LaCoO3 a continuous low to intermediate to high-spin transition w hich gives rise to heat capacity maxima at T approximate to 60 K, and at T approximate to 530 K. Energetic aspects of the transitions are di scussed. The thermodynamic properties have been evaluated, and the val ues of the molar heat capacities, entropies, and enthalpies for LaFeO3 and LaCoO3 at T = (298.15, 900, 298.15, and 1000) K, respectively, ar e:[GRAPHICS] (C) 1998 Academic Press Limited.