SIMULTANEOUS THERMOGRAVIMETRY MASS-SPECTROMETRY FOR A SOLID OXIDE FUEL-CELL INTERCONNECT, (LA0.7CA0.32)CRO31

TG-MS simultaneous measurement on a nominally chromium deficient lanth anum calcium chromite, (La0.7Ca0.32)CrO3, has been made in a helium fl ow and the results were compared with its shrinkage behavior in air an d also with TG-DTA results on related calcium chromium oxides (n(CaO)/ n(CrOx) = 1:1 and 5:3) in air. In addition to evolution of water (320- 920 K and 1020-1120 K) and carbon dioxide (340-1120 K), four distinct oxygen evolution peaks were observed from 900 to 1600 K; this oxygen e volution can be ascribed to the successive reduction of chromium ions in second phases which were estimated as about 1 mol% of Ca-5 (CrO4)(3 ) or 2 mol% of Ca-3(CTO4)(2). With the aid of available phase diagrams , a peak of simultaneous water and oxygen evolution at 1020-1120 K was attributed to the decomposition of an intermediate reaction compound, Ca-5(CTO4)(3)OH. Similarly, the water evolution at 320-920 K and CO2 evolution can be ascribed to the decomposition of hydrated calcium chr omates, CaCrO4 . nH(2)O and calcium carbonate which were considered to be formed as reaction products of Ca-5(CrO4)(3) with water, oxygen, a nd carbon dioxide. These features were discussed in relation to the si ntering behavior of chromium deficient lanthanum calcium chromite.