Effect of Oxide Additives on Sintering of LaMnO₃ Bodies

Abstract

The effects of oxide additives on the sintering of LaMnO₃ have been discussed on the basis of the isothermal shrinkage, bulk density and grain size at 1300-1450°C for 0.25-70 hr in air. The lattice constants of LaMnO₃ with various oxide additives were measured by X-ray diffraction analysis with the internal standard of 99.99% Si.
The results were summarized as follows; (1) It was shown that sintering was markedly promoted by the addition of ZrO₂, ZnO and BaO, while it was not promoted by the addition of Fe₂O₃ and TiO₂ in low temperature range. (2) The results of shrinkage measurement of pure LaMnO₃ and modified LaMnO₃ with various oxide additives indicated that a constant value of m obtained in the initial stage was about 0.50. (3) The rate of grain growth was found to be followed by the equation Dⁿ-D₀ⁿ=kt; the values of time exponent n for pure LaMnO₃ with TiO₂ and CaO additives of 5 mol% were about 2.5, 2.3 and 2.6, and the values of the activation energy were estimated to be 76, 63 and 78 kcal/mol, respectively. (4) LaMnO₃ and LaMnO₃ with oxide (ZrO₂, ZnO and BaO) additives were determined to be perovskite type with orthorhombic unit cell by X-ray diffraction analysis. It was recognized that lattice constants of LaMnO₃ were varied by oxide additives up to 10 mol%.