Temperature Dependent Crystal Structure of Nd2CuTiO6: An In Situ Low Temperature Powder Neutron Diffraction Study

Herein we reported the crystal structure and crystal chemistry of orthorhombic perovskite type Nd2CuTiO6 in between 2 K and 290 K as observed from the in situ temperature-dependent powder neutron diffraction (PND) studies. It is observed that the cations in octahedral sites are statistically occupied, and the ambient temperature orthorhombic structure is retained throughout the temperature range of the study. Absence of any long-range magnetic ordering down to 2 K is confirmed by both low-temperature PND and magnetization studies. The lattice shows strong anisotropic thermal expansion with increasing temperature, viz. almost no or feeble negative expansion along the a-axis while appreciably larger expansion along the other two axes (alpha(b) = 10.6 x 10(-6) K-1 and alpha(c) = 9.8 x 10(-6) K-1). A systematic change in the rotation of octahedral units with temperature was observed in the studied temperature range, while the expansion of unit cells is predominantly associated with the polyhedral units around the Nd(3)Ions. The temperature-dependent relative change in unit cell parameters as well as coefficients of axial thermal expansion show anomalous behavior at lower temperatures, and that seems to be related to the electronic contributions to lattice expansion.

Automated summary

In this study, the crystal structure and crystal chemistry of orthorhombic perovskite type Nd2CuTiO6 were analyzed using in situ temperature-dependent powder neutron diffraction (PND) studies. It was found that the cations in octahedral sites are statistically occupied and the orthorhombic structure remains stable across the entire temperature range. No long-range magnetic ordering was observed at temperatures as low as 2 K. The lattice exhibited strong anisotropic thermal expansion, with almost no or very little negative expansion along the a-axis but significant expansion along the other two axes. The rotation of octahedral units varied systematically with temperature, while the expansion of unit cells was mainly associated with the polyhedral units around the Nd(3) ions. The temperature-dependent changes in unit cell parameters and axial thermal expansion coefficients showed anomalous behavior at lower temperatures, which may be attributed to the electronic contributions to lattice expansion.