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Phase Transitions in the Metastable Perovskite Multiferroics BiCrO3 and BiCr0.9Sc0.1O3: A Comparative Study
journal contribution
posted on 2020-06-09, 23:43 authored by João
Pedro Cardoso, Davide Delmonte, Edmondo Gilioli, Elena L. Fertman, Alexey V. Fedorchenko, Vladimir V. Shvartsman, Vaidotas Paukšta, Robertas Grigalaitis, Ju̅ras Banys, Dmitry D. Khalyavin, Joaquim M. Vieira, Andrei N. SalakThe
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 √6ap × √2ap × √6ap superstructure (where ap is the primitive
perovskite unit-cell parameter) under ambient conditions. At room
temperature, the unit cell volume of BiCr0.9Sc0.1O3 is ∼1.3% larger than that of BiCrO3. Both perovskites undergo a reversible structural transition into
a nonpolar GdFeO3-type phase (orthorhombic Pnma, √2ap × 2ap × √2ap) 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 Néel temperature (TN) of about 85 K as compared with TN = 110 K in BiCrO3. In contrast to BiCrO3, which exhibits a spin reorientation at Tsr ∼ 72 K, no such a transition occurs in BiCr0.9Sc0.1O3.