resumo
The temperature behavior of the crystal structure as well as dielectric and magnetic properties of the perovskite bismuth chromate ceramics with the 10 mol % Cr3+-to-Sc3+ substitution were studied and compared with those of the unmodified compound. Using a high-pressure synthesis, BiCrO3 and BiCr0.9Sc0.1O3 were obtained as metastable perovskite phases which are monoclinic C2/c with the root 6a(p) x root 2a(p) x root 6a(p) superstructure (where a(p) is the primitive perovskite unit-cell parameter) under ambient conditions. At room temperature, the unit cell volume of BiCr0.9Sc0.1O3 is similar to 1.3% larger than that of BiCrO3. Both perovskites undergo a reversible structural transition into a nonpolar GdFeO3-type phase (orthorhombic Pnma, root 2a(p) x 2a(p) x root 2a(p)) in the temperature ranges of 410-420 K (BiCrO3) and 470-520 K (BiCr0.9Sc0.1O3) with a relative jump of the primitive perovskite unit cell volume of about -1.6 and -2.0%, respectively. Temperature dependences of the complex dielectric permittivity demonstrate anomalies in the phase transition ranges. The Pnma-to-C2/c crossover in BiCrO3 is accompanied by a decrease in the direct current (dc) conductivity, while in BiCr0.9Sc0.1O3 the conductivity increases. The onset of an antiferromagnetic order in BiCr0.9Sc0.1O3 is observed at the Neel temperature (TN) of about 85 K as compared with T-N = 110 K in BiCrO3. In contrast to BiCrO3, which exhibits a spin reorientation at T-sr similar to 72 K, no such a transition occurs in BiCr0.9Sc0.1O3.
palavras-chave
DIELECTRIC-RELAXATION; MAGNETIC-PROPERTIES; CRYSTAL
categoria
Chemistry
autores
Cardoso, JP; Delmonte, D; Gilioli, E; Fertman, EL; Fedorchenko, AV; Shvartsman, VV; Pauksta, V; Grigalaitis, R; Banys, J; Khalyavin, DD; Vieira, JM; Salak, AN
nossos autores
Andrei Salak
Investigador Principal
João Pedro Veleirinho Cardoso
Estudante de doutoramentoagradecimentos
J.P.C. acknowledges FCT - Fundacao para a Ciencia e Tecnologia, Portugal, for Ph.D. grant SFRH/BD/145281/2019. The research performed in the University of Aveiro was developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through the FCT/MEC and when appropriate cofinanced by FEDER under the PT2020 Partnership Agreement.