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.

Reports:

2025

2026

2027