Papers by Keyword: LaCrO₃

Abstract: The equilibrium structures of orthorhombic LaCrO₃ (O-LaCrO₃) and rhombohedral LaCrO₃ (R-LaCrO₃) crystals were investigated by using the plane-wave self consistent field (PWSCF) method based on density functional theory (DFT). The optimized lattice parameters for both phases are in accordance with experimental results reported in literature, confirming the reliability of LSDA+U scheme used in the calculations. We have quantificationally investigated the binding energies and electronic properties of these two types of LaCrO₃ crystals. The negative total energy and binding energies indicate the ground state property and the good structrual stability of O-LaCrO₃ crystal, which is important for the preparation of nano materials, the synthesis of ceramic materials made of doped O-LaCrO₃ crytals, as well as their applications in high technology fields, and predict the metastable property of R-LaCrO₃ crystal. Furthermore, the band structures show that O-LaCrO₃ is a direct semiconductor with wide energy gap, while R-LaCrO₃ is an indirect semiconductor with narrow energy gap. The interaction between Cr and O atoms in O-LaCrO₃ crystal possesses the character of covalent bonding.

Abstract: Effect of different blending amount of LaCrO₃, a composite additive, on the hydration resistance and crystallization properties of magnesia-calcium refractory were studied by measuring hydration rate, using X-ray diffraction and scanning electron microscopy. The results show that the LaCrO₃ at a low addition (≤1%) can significantly decrease the hydration resistance of the MgO-CaO material when the burning temperature is 1550°C, and the hydration rate is only 0.183%. LaCrO₃ can promote the growth of the CaO, while it has little effect on MgO. The Cr₂O₃ and CaO can melt into CaO·Cr₂O₃ in a high temperature. The CaO·Cr₂O₃ can not only promote sintering but also wrap on the CaO, which is negative for the grain to contact with water, and consequently improve the hydration resistance of magnesia-calcium refractory.