Preparation and Thermochemical Properties of BaNiO2+x

✍ Scribed by Joseph DiCarlo; Iman Yazdi; Allan J. Jacobson; Alexandra Navrotsky

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 209 KB
• Volume: 109
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1994.1096

✦ Synopsis

Single crystals of (\mathrm{BaNiO}{3}) have been synthesized in molten (\mathrm{KOH}). The enthalpies of formation from the component oxides at (25^{\circ} \mathrm{C}) of (\mathrm{BaNiO}{2}, \mathrm{BaNiO}{2.63}), and (\mathrm{BaNiO}{3}) have been measured using high temperature reaction calorimetry. As the value of (x) increases in (\mathrm{BaNiO}{2+x}), the enthalpy of formation becomes more exothermic. From the enthalpy of formation data, an enthalpy of oxidation of (-196 \pm 20 \mathrm{~kJ} /\left(\right.) mole (\left.\mathrm{O}{2}\right)) was obtained. This value is very similar to the values of (-202 \pm 18) and (-220 \pm 50 \mathrm{~kJ} /\left(\right.) mole (\left.{2}\right)) obtained for (\mathrm{YBa}{2} \mathrm{Cu}{3} \mathrm{O}{7-y}) and (\mathrm{La}{2-x} \mathrm{Ba}{x} \mathrm{CuO}_{4-y}), respectively (\mathrm{Z}). Zhou, and A. Navrotsky, J. Mater. Res. 7(11), 2920 (1992); J. DiCarlo, J. Bularzik, and A. Navrotsky, J. Solid State Chem. 96, 381 (1992). Energetic and structural data are discussed in terms of a model in which the holes have significant oxygen character [A. Mehta, J. DiCarlo, and A. Navrotsky, J. Solid State Chem. 101, 173 (1992).] O 1994 Academic Press, Inc.