Shape-Tunable BaTiO₃ Crystals Presenting Facet-Dependent Optical and Piezoelectric Properties

Area of Science:

• Materials Science
• Nanotechnology
• Solid State Physics

Background:

• Barium titanate (BaTiO3) is a versatile perovskite material with significant ferroelectric, piezoelectric, and pyroelectric properties.
• Controlling the morphology and size of BaTiO3 crystals is crucial for tailoring their physical characteristics and device performance.
• Surface and facet-dependent properties of nanomaterials are increasingly recognized as critical factors in their functionality.

Purpose of the Study:

• To synthesize BaTiO3 crystals with controlled morphologies (octahedra, truncated cubes, cubes) and tunable sizes.
• To investigate the impact of crystal shape and size on the piezoelectric, ferroelectric, pyroelectric, and dielectric properties of BaTiO3.
• To fabricate and evaluate the performance of piezoelectric nanogenerators based on different BaTiO3 morphologies.

Main Methods:

• Solvothermal synthesis approach for BaTiO3 crystal fabrication.
• Acetic acid treatment for impurity removal (BaCO3).
• Rietveld refinement of X-ray diffraction and Raman spectroscopy for structural and phase confirmation.
• Fabrication of piezoelectric nanogenerators using synthesized BaTiO3 crystals.

Main Results:

• Successfully synthesized BaTiO3 crystals in various shapes and sizes (132–438 nm).
• Confirmed tetragonal crystal structure and identified size- and facet-dependent bandgap shifts.
• BaTiO3 octahedra demonstrated enhanced piezoelectric, ferroelectric, and pyroelectric effects compared to cubes.
• Nanogenerators using BaTiO3 octahedra exhibited superior performance, with a 30 wt.% octahedra device reaching 23 V open-circuit voltage and 324 nA short-circuit current.
• Device performance was stable, with a maximum output power of 3.9 µW at 60 MΩ, capable of powering LEDs.

Conclusions:

• The morphology of BaTiO3 crystals significantly influences their physical properties, particularly piezoelectric, ferroelectric, and pyroelectric responses.
• Octahedral BaTiO3 crystals are optimal for high-performance piezoelectric nanogenerator applications.
• This study underscores the critical role of surface dependence in determining the functional properties of semiconductor crystals.