期刊
ACS APPLIED ELECTRONIC MATERIALS
卷 2, 期 10, 页码 3211-3220出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsaelm.0c00559
关键词
high-entropy oxides; hydrothermal synthesis; multicomponent equiatomic perovskites; quenching; antiferromagnetic semiconductor
资金
- EU Project [POWR.03.02.00-00-I004/16]
- National Science Centre, Poland [UMO-2017/27/N/ST5/01635]
- PLGrid Infrastructure
Single-phase multicomponent perovskite-type cobalt oxide containing five cations in equiatomic amounts on the A-site, namely, (Gd0.2Nd0.2La0.2Sm0.2Y0.2)CoO3, has been synthesized via the modified coprecipitation hydrothermal method. Using an original approach for heat treatment, which comprises quenching utilizing liquid nitrogen as a cooling medium, a single-phase ceramic with high configuration entropy, crystallizing in an orthorhombic distorted structure was obtained. It reveals the anomalous temperature dependence of the lattice expansion with two weak transitions at approx. 80 and 240 K that are assigned to gradual crossover from the low- via intermediate- to high-spin state of Co3+. The compound exhibits weak ferromagnetism at T <= 10 K and signatures of antiferromagnetic correlations in the paramagnetic phase. Ab initio calculations predict a band gap Delta = 1.18 eV in the ground-state electronic structure with the dominant contribution of O_p and Co_d orbitals in the valence and conduction bands, respectively. Electronic transport measurements confirm the negative temperature coefficient of resistivity characteristic to a semiconducting material and reveal a sudden drop in activation energy at T similar to 240 K from E-a similar to 1 eV in the low-temperature phase to E-a similar to 0.3 eV at room temperature. The possibility of fine tuning of the semiconducting band gap via a subtle change in A-site stoichiometry is discussed.
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