“True” negative thermal expansion in Mn-doped LaCu3Fe4O12 perovskite oxides

摘要

Negative and zero thermal expansion near room temperature have been achieved in a cubic A-site ordered perovskite oxide LaCuFeMnO. A discontinuous volume change in the parent material LaCuFeO, owing to a first-order intermetallic charge transfer transition (3Cu+ 4Fe ⇄ 3Cu+ 4Fe), is efficiently relaxed to a second-order-type negative thermal expansion with a linear thermal expansion coefficient (α) of −2.2(1) × 10K between 300 and 340 K at x = 0.75, followed by an almost zero thermal expansion [α of −1.1(2) × 10K] at x = 1 in a wide temperature range (240–360 K) including room temperature. Magnetic susceptibility measurements display substantial broadenings of the antiferromagnetic transition when x increases, supporting the relaxation of first-order electronic phase transition of the parent material. These findings indicate that the significant adjustability of thermal expansion properties can be achieved in first-order intermetallic charge-transfer transition.