Negative thermal expansion of Ca<sub>2</sub>RuO<sub>4</sub> with oxygen vacancies

Negative thermal expansion of Ca₂RuO₄ with oxygen vacancies

Xu Sen¹, Hu Yangming¹, Liang Yuan^{2, †}, Shi Chenfei³, Su Yuling³, Guo Juan¹, Gao Qilong¹, Chao Mingju¹, Liang Erjun^{1, ‡}

Thermal expansion property: (a) relative length change of ceramic cylinders measured by dilatometry; (b)–(e) changes of lattice constants, lattice volume, and (f) the Ca–Ru distance for (b) Ca₂RuO_4.09, (c) Ca₂RuO_3.87, and (d) Ca₂RuO_3.73 with temperature. The insert shows the octahedron rotation about the c-axis and tilt about an axis in the Ru–O(1) plane.