The functional properties of ferroelectric materials are strongly influenced by their spontaneous polarization and the crystallographic phase. The most known ferroelectric, barium titanate, suffers three phase transitions when increasing the temperature, which are also accompanied by enhancements in dielectric, ferroelectric, piezoelectric or pyroelectric properties. Among all phase transitions, the closest to the room temperature and the most promising to be exploited is the orthorhombic-tetragonal phase transition. The structural phases of barium titanate were generally investigated in thin films and single crystals, but more recent studies in ceramics showed that the phase transitions do not occur at certain temperature values, but rather in a range of temperatures characterized by phase superpositions. Another advantageous ceramic effect is that the application of an electric field can induce the transformation of many grains in orthorhombic phase, which is characterized by larger values of polarization. The main objective of this project is to investigate the role of phase superposition on the functional properties of ferroelectric ceramics by a combined experimental-modeling approach. After understanding this mechanism, the project aims to design other barium titanate-based ceramic materials (with controlled compositions and morphologies) with appropriate phase superpositions and improved functional properties.

The project aims to demonstrate that polymorphic phase superposition in BaTiO₃-based ferroelectric ceramics can be intentionally controlled and exploited to design materials with enhanced dielectric, piezoelectric, and pyroelectric properties at room temperature. The approach integrates Landau–Ginzburg–Devonshire (LGD) theory with advanced 3D Finite Element Method (FEM) simulations, enabling predictive modeling of phase coexistence under realistic microstructural, electrical, and mechanical conditions.

Objective O1 – Identify conditions that favor phase superposition.
The project examines how small homovalent substitutions (e.g. Zr, Sn, Hf, Ce), porosity level, and microstructural constraints shift and broaden the orthorhombic–tetragonal (O–T) transition near room temperature. Dense, porous, and composite BaTiO₃-based ceramics will be synthesized, while a new combined FEM–LGD modeling framework will map the parameters that stabilize mixed-phase states.

Objective O2 – Evaluate the impact of phase superposition on functional properties.
Selected compositions exhibiting O–T coexistence will be analysed to determine how the polymorph ratio affects permittivity, tunability, hysteresis, and high-field responses. A specific focus is placed on understanding how poling conditions (field amplitude, sequence, temperature) induce or suppress phase transformations, and how these transformations correlate with improvements in piezoelectric and pyroelectric coefficients.

Objective O3 – Design new ceramics with optimized phase coexistence.
Based on the insights from O1 and O2, the FEM–LGD model will be used to design materials and composite architectures that intentionally exploit phase superposition to maximize performance. The most promising predicted systems will be fabricated and experimentally validated.

Publications in ISI journals:

1. Grain size effects in BaTi₉₀Hf_0.10O₃ceramics with phase coexistence: the influence of nanostructuring and of the internal stress on the functional properties, Journal of Materials Research and Technology, E. M. Soare, C.-A. Stanciu, R. E. Patru, V.-A. Surdu, L. Padurariu, N. Horchidan, A.-I.¸ Nicoara, L. Trupina , B. S. Vasile, R. D. Trusca, L. Mitoseriu , A.-C. Ianculescu, 38 (2025) 5389–5408

Participation to international conferences:

1. Padurariu, The impact of phase superposition in barium titanate- based ceramics on the functional properties, 8th International Conference on MATERIALS SCIENCE & NANOTECHNOLOGY, June 25-26, 2025 at Prague, Czech Republic (virtual plenary)
2. Leontin Padurariu, Radu S. Stirbu, Alexandru V. Lukacs, Nadejda Horchidan, Cristina E. Ciomaga, and Liliana Mitoseriu, Finite Element Method for describing functional properties, 16th ECerS Conference for Young Scientists in Ceramics, Novi Sad, Serbia, 15-18.10.2025 (Invited talk)
3. Cristina E. Ciomaga, Leontin Padurariu, Nadejda Horchidan, Radu-Stefan Stirbu, Felicia Gheorghiu, Alexandru-Vlad Lukacs, and Liliana Mitoseriu, Engineering porosity in BaTiO₃-based ceramics for tunable functional properties and energy harvesting applications, 15th EMF and PLU7, Katowice, Poland, 31.08-5.09.2025 (Invited talk)
4. Radu Stefan Stirbu, Leontin Padurariu, Fereshteh Falah Chamasemani, Roland Brunner, Vlad A. Lukacs, Cristina Elena Ciomaga, Liliana Mitoseriu, Local vs. macroscopic dielectric and ferro/piezoelectric responses in porous BaTiO3 ceramics determined on the basis of 3D reconstructed ceramic microstructures, FEMS2025 EUROMAT, Granada, Spain, 14-19.09.2025 (oral presentation)
5. Cristina E. Ciomaga, Felicia Gheorghiu, Anda Oajdea, Nadejda Horchidan, Alexandru-Vlad Lukacs, Leontin Padurariu, and Liliana Mitoseriu, Exploring the effect of phase superposition in BaTiO₃- solid solution ceramics for enhanced functional properties, FEMS2025 EUROMAT, Granada, Spain, 14-19.09.2025 (poster presentation)
6. Felicia Gheorghiu, Nadejda Horchidan, Viorica Vasilache, Ionut Topală and Cristina Elena Ciomaga, Exploring multifunctional properties of BaTiO₃ –based ceramics by addition of multi-walled carbon nanotubes, FEMS2025 EUROMAT, Granada, Spain, 14-19.09.2025 (poster presentation)

The cognitive impact of the SUPERFER project is related to the advancement of fundamental knowledge on the mechanisms that control phase superposition in ferroelectric ceramics and on the way this phenomenon can be used to improve functional properties. The project addresses BaTiO₃-based ceramics, where the coexistence of different crystallographic polymorphs, especially the orthorhombic and tetragonal phases, may strongly influence dielectric, ferroelectric, piezoelectric and pyroelectric responses. By investigating the relationships between composition, microstructure, local polarization, internal electric fields, mechanical stress and phase stability, the project contributes to a deeper understanding of the physical origin of enhanced functional properties in lead-free ferroelectric materials.
A major scientific contribution of the project is the development of an integrated modelling approach that combines the Finite Element Method with the Landau–Ginzburg–Devonshire theory. This FEM–LGD framework allows the description of local electric fields, depolarizing effects, stress/strain distributions, polarization states and crystallographic phase stability in realistic polycrystalline ferroelectric ceramics. In this way, the project extends the local field engineering concept toward a broader strategy in which phase superposition becomes a controllable design parameter rather than only a structural observation. The first-stage results have already shown that phase coexistence can be influenced by chemical substitution, temperature, grain size, porosity, internal stress and electrical or mechanical boundary conditions.
The project also contributes to the transition from empirical materials optimization toward predictive and physically grounded materials design. Instead of relying exclusively on trial-and-error experimental approaches, the numerical models developed within the project can guide the selection of promising compositions and microstructures before experimental validation. In the first stage, Ba(ZrₓTi₁₋ₓ)O₃ compositions with low Zr content were identified as relevant systems for stabilizing orthorhombic–tetragonal phase coexistence near room temperature. The synthesis and characterization of BaTiO₃ and Ba(ZrₓTi₁₋ₓ)O₃ ceramics provided experimental support for the theoretical predictions, including the formation of perovskite phases, the occurrence of tetragonal–orthorhombic coexistence and the sensitivity of dielectric properties to small compositional and microstructural changes.
From a socio-economic perspective, the project has relevance for the medium- and long-term development of advanced functional materials used in microelectronics, sensors, actuators, transducers, capacitors, tunable components, energy harvesting systems and energy-efficient devices. Although the project is primarily fundamental and exploratory, improving the understanding and predictability of ferroelectric and piezoelectric properties may support the future development of more efficient, reliable and application-oriented lead-free materials. The modelling-guided design strategy may also reduce the consumption of raw materials, energy and experimental time by limiting the number of compositions and processing routes that need to be tested experimentally.
The project further contributes to the consolidation of research capacity at UAIC by strengthening expertise in computational physics, electroceramics, numerical modelling and advanced functional materials. It supports the training of young researchers in interdisciplinary methods that combine physics, materials science, numerical simulation, ceramic processing and electrical characterization. Through scientific publications, international conference presentations and dissemination activities, the project increases the visibility of the research team and contributes to the international recognition of Romanian research in the field of ferroelectric and multifunctional materials.

Reports:

2025

2026

2027