The pressure-induced crystal structure transformations in the high-pressure annealed Bi1 − x Tb x FeO3 compounds ( x   =  0.05, 0.1, and 0.3)

The substitution of Bi by rare-earth ions is one of the common approaches for improving the electrical, magnetic, and multiferroic properties of the most studied multiferroic material BiFeO3. In this work, Bi1−xTbxFeO3 compounds with x = 0.05, 0.1, and 0.3 were synthesized using a two-step process: standard solid-state synthesis and high-pressure annealing. The obtained samples were studied by means of x-ray diffraction at normal pressure and neutron powder diffraction at high pressure. It was shown that high-pressure annealing could increase the Tb solubility limit to 10 at. %. It is proposed that the maximum solubility limit is even higher and could be achieved with high-pressure annealing in bulk samples. The transition from the R3c phase to the Pnma phase for the compounds with x = 0.05, 0.1 occurs through a two-phase region and starts at P≈4.4 and 1.7 GPa, respectively. The Pnma phase is stable in the compound with x = 0.3 up to P≈3.2 GPa. The values of Fe magnetic moments decrease with an increase in the Tb concentration or with external pressure for the compounds with x=0.05,0.3 in one-phase regions. The results will help to optimize the synthesis of multiferroic materials with improved magnetoelectric coupling for use in technological applications.