Core-Shell Piezoelectric Composition for High d33
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional piezoelectric compositions, such as those based on bismuth ferrite, face challenges in achieving high piezoelectric constants (d33) and stability under electric fields, with existing lead-free alternatives like barium titanate-bismuth ferrite compositions exhibiting low d33 values and high anisotropy.
Innovation Solution
A piezoelectric composition comprising bismuth, iron, barium, titanium, and oxygen with a core-shell structure, where the bismuth content is lower in the core than in the shell, and the proportion of core-shell particles is between 0.10 to 1.00, enhancing the piezoelectric constant d33 to 200 pC/N or more when an electric field of 0.1 to 2.0 kV/mm is applied.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If lead-free piezoelectric compositions are used to eliminate environmental harm, then environmental safety is improved, but piezoelectric performance (d33 constant) deteriorates
Solution Approach 1:
The invention uses a composite structure consisting of a core region and a shell region with different chemical compositions. The core contains barium titanate and bismuth ferrite in a specific ratio, while the shell contains bismuth ferrite and bismuth magnesate titanate, creating a composite material that achieves both environmental safety and high piezoelectric performance
Solution Approach 2:
The invention applies local quality by creating regions with different compositions within the same crystal particle. The core has a specific BaTiO3-BiFeO3 composition ratio optimized for piezoelectric properties, while the shell has a different composition with added Bi-Mg-Ti phase to control anisotropy and leakage current, allowing each region to contribute different functional properties
2Temperature
If bismuth ferrite is used to achieve high Curie temperature, then thermal stability is improved, but leakage current increases and piezoelectric performance deteriorates
Solution Approach 1:
The shell region specifically addresses the leakage current issue by incorporating Bi-Mg-Ti phase that forms a protective layer at the grain boundaries, reducing leakage current while the core region maintains the high Curie temperature through its BaTiO3-BiFeO3 composition
Solution Approach 2:
The Bi-Mg-Ti phase in the shell acts as an intermediary between the high-Curie-temperature core and the external environment, mediating the electrical properties by reducing leakage current at grain boundaries while preserving the thermal stability of the core
3Temperature
If binary compound of barium titanate and bismuth ferrite is used to achieve high Curie temperature, then thermal stability is improved, but anisotropy increases and piezoelectric performance deteriorates
Solution Approach 1:
The invention creates a composite structure where the shell region contains Bi-Mg-Ti phase that forms a protective layer, reducing the harmful effects of anisotropy while maintaining the high Curie temperature properties of the BaTiO3-BiFeO3 core
Solution Approach 2:
The Bi-Mg-Ti phase in the shell acts as an intermediary that mitigates the anisotropy problem by forming a protective layer at grain boundaries, allowing the core to maintain its high Curie temperature without suffering from excessive anisotropy
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The core-shell structure improves the piezoelectric characteristics by facilitating easier polarization reversal, resulting in a higher piezoelectric constant d33 and enhanced performance in piezoelectric devices, even under lower electric field strengths compared to conventional BiFeO3-based devices.
Implementation Method 1
a piezoelectric composition comprising a plurality of crystal particles, wherein the piezoelectric composition includes bismuth, iron, barium, titanium and oxygen
Data Source
AI summary
A piezoelectric composition comprises a plurality of crystal particles, wherein the piezoelectric composition includes bismuth, iron, barium, titanium, and oxygen; the crystal particles include a core and a shell covering the core; the average value of the contents of bismuth in the cores is expressed as CCORE % by mass, the average value of the contents of bismuth in the shells is expressed as CSHELL % by mass, and the CCORE is lower than the CSHELL; and the number of all the particles comprised in the piezoelectric composition is expressed as N, the number of the crystal particles including the core and the shell is expressed as n, and n/N is 0.10 to 1.00.