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Equimolar powder mixtures and multilayer pellets of single‐phase Sr‐doped lanthanum manganite perovskite materials Lay‐xSrxMnO3 with La content y = 1 and 0.95 and Sr content 0 ≤ x ≤ 0.5 were annealed in air with 8 mol% Y2O3‐ZrO2 at 1470 K, up to 400 h and at 1670 K. up to 200 h. X‐ray diffraction and electron probe microanalysis confirmed the formation of La2Zr2O7 or SrZrO3 depending on the composition of the perovskites. No reaction products could be detected for La0.95‐xSr xMnO3 with 0.2 ≤ x ≤ 0.4 after annealing for 400 h at 1470 K, and for the perovskite La0.65Sr0.3MnO3 even after annealing for 200 h at 1670 K. The results demonstrate the improved chemical compatibility of La‐deficient perovskites against reaction with zirconia and can provide a basis for the selection of a sufficiently chemically stable material for the air electrode of solid oxide fuel cells.

The low-temperature specific heat and electrical resistivity of the polycrystalline non-stoichiometric manganites La 0.95−x Sr x MnO 3 have been investigated in the doping region x = 0.00-0.30. The specific heat has terms proportional to T and T 3 . The resistivity of the samples decreases as T 1/2 with increasing temperature, goes through a minimum and then increases proportionally to T 3 . The temperature T min , corresponding to the minimum of the resistivity, shifts with Sr content as T min ∼ x −2/5 .

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The resistivity minimum in manganites is still under debate. Recent publications discussed two possible scenarios: (i) electron–electron interaction in weak disordered systems and (ii) charge carriers tunnelling between antiferromagnetic coupled grains. In order to resolve this puzzle, we present a systematic study on the electrical resistivity, ρ(T), which was carried out in ceramic samples of La0.75Sr0.20MnO3 and La0.75Sr0.20Mn1−cCocO3 manganites over the temperature ranges 0.4–60 K and 4–60 K respectively. All compounds show a minimum in the resistivity at a characteristic temperature Tmin, which in the Co-doped samples shifts towards higher temperatures as the Co concentration increases. Tmin varies approximately as c1/3. The application of an external magnetic field shows that the Tmin decreases linearly as the field increases, and above 0.7 T remains field independent. In magnetic fields, where Tmin is constant, Tmin varies as . For temperatures below Tmin the resistivity data can be fitted either with a or with a −lnT function, while for temperatures above the minimum the resistivity follows both a T3 and a T5/2 dependence. We believe that there is a crossover between a ‘Kondo-like’ scattering process and the 3D electron–electron interaction effects enhanced by disorder.