Peculiarities of the crystal structure evolution of Bifeo3-batio3 ceramics across structural phase transitions

Evolution of the crystal structure of ceramics BiFeO3-BaTiO3 across the morphotropic phase boundary was analyzed using the results of macroscopic measuring techniques such as X-ray diffraction, differential scanning calorimetry, and differential thermal analysis, as well as the data obtained by local scale methods of scanning probe microscopy. The obtained results allowed to specify the concentration and temperature regions of the single phase and phase coexistent regions as well as to clarify a modification of the structural parameters across the rhombohedral-cubic phase boundary. The structural data show unexpected strengthening of structural distortion specific for the rhombohedral phase, which occurs upon dopant concentration and temperature-driven phase transitions to the cubic phase. The obtained results point to the non-monotonous character of the phase evolution, which is specific for metastable phases. The compounds with metastable structural state are characterized by enhanced sensitivity to external stimuli, which significantly expands the perspectives of their particular use. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Instituto Nacional de Ciência e Tecnologia para Excitotoxicidade e Neuroproteção, INCT-EN: UID/04564/2020, UIDB/50011/2020, UIDP/50011/2020Russian Science Foundation, RSF: 18-19-00307Funding: This work was supported by the RSF (project #18-19-00307). Investigations performed at the Center for Physics of the University of Coimbra were supported by Fundação para a Ciência e a Tecnologia (project UID/04564/2020). M.V.S. acknowledges Russian academic excellence project “5-100” for Sechenov University. Part of work done at the University of Aveiro was developed within the scope of the project CICECO-Aveiro Institute of Materials, refs. UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through the FCT/MEC

Crystal structure and magnetic properties of Bi1-xSmxFeO3 ceramics across the phase boundary: effect of high pressure

The solid solutions Bi1-xSmxFeO3 with chemical composition across the morphotropic phase boundary region specific for rhombohedral - orthorhombic structural transition were investigated by X-ray diffraction, electron microscopy and magnetometry. Structural measurements showed a concentration driven transition from the single phase rhombohedral structure to the single phase nonpolar orthorhombic structure through the formation of antipolar orthorhombic phase which coexists with the rhombohedral phase in the compounds with x < 0.15 followed by a coexistence with nonpolar orthorhombic phase in the compounds with x <= 0.18. Application external pressure provides a stabilization of the orthorhombic phase, viz. the polar rhombohedral phase diminishes and transforms to the anti-polar orthorhombic phase, while the anti-polar orthorhombic phase transforms to the non-polar orthorhombic phase. Magnetic properties of the compounds subjected to external pressure demonstrate an increase in the magnetization of the compounds having dominant rhombohedral phase, wherein coercivity significantly increases, while the spontaneous magnetization remains nearly constant. Твердые растворы Bi1-xSmxFeO3 с химическим составом в области морфотропной границы раздела фаз, характерной для ромбоэдрально-орторомбического структурного перехода, были исследованы методами рентгеновской дифракции, электронной микроскопии и магнитометрии. Структурные измерения показали обусловленный концентрацией переход от однофазной ромбоэдрической структуры к однофазной неполярной орторомбической структуре путем образования антиполярной орторомбической фазы, которая сосуществует с ромбоэдрической фазой в соединениях с x < 0,15, за которым следует сосуществование с неполярной орторомбической фазой в соединениях с x <= 0,18. Применение внешнего давления обеспечивает стабилизацию орторомбической фазы, а именно. полярная ромбоэдрическая фаза уменьшается и переходит в антиполярную орторомбическую фазу, в то время как антиполярная орторомбическая фаза переходит в неполярную орторомбическую фазу

Crystal structure and magnetic properties of (1-x)BiFeO3 - xBaTiO3 ceramics across the phase boundary

Кристаллическая структура и магнитные свойства бессвинцовой керамики (1-x)BiFeO3 - xBaTiO3 (x<0,40) приготовленной методом твердофазной реакции, были изучены в зависимости от химического состава и температура. The crystal structure and magnetic properties of lead-free ceramics (1-x)BiFeO3 - xBaTiO3 (x<0.40) prepared by solid state reaction method were studied depending on the chemical composition and temperature