Lead-Free Piezoelectric Material for High Curie Temperature
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing lead-free piezoelectric materials face challenges in achieving both high piezoelectric performance and high Curie temperature, with previous attempts either compromising on performance or temperature, and there is a need for materials suitable for high-temperature device operations without using lead.
Innovation Solution
A piezoelectric material with a perovskite-type metal oxide structure expressed by the formula xBaTiO3-yBiFeO3-zBi(M0.5Ti0.5)O3, where M represents Mg or Ni, with specific ratios of x, y, and z, achieving a diffuse phase transition structure and high Curie temperature, is developed, allowing for both high piezoelectric performance and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If barium titanate is used as a lead-free piezoelectric material, then environmental safety is improved, but Curie temperature is limited to 125°C
Solution Approach 1:
The patent creates a composite piezoelectric material by forming a solid solution between barium titanate (BaTiO3) and bismuth ferrite (BiFeO3). This composite approach combines the environmental safety of lead-free barium titanate with the high Curie temperature characteristic of bismuth ferrite, achieving both goals simultaneously. The solid solution structure allows atomic-level mixing of the two materials, creating a new phase with properties superior to either parent material alone.
Solution Approach 2:
The patent systematically varies the compositional parameters (mole ratios of BaTiO3 and BiFeO3) to optimize the Curie temperature while maintaining piezoelectric performance. By controlling the concentration of bismuth ferrite in the solid solution, the invention achieves a Curie temperature of 200°C or higher, representing a 75°C increase over pure barium titanate while retaining lead-free composition.
2Temperature
If bismuth ferrite is added to increase Curie temperature, then Curie temperature is improved, but piezoelectric performance is conspicuously decreased
Solution Approach 1:
The patent identifies and controls the optimal compositional range, specifying that the mole ratio of BiFeO3 (y) should be 0.1 to 0.4. Within this precisely defined parameter range, the invention achieves both high Curie temperature (200°C or higher) and satisfactory piezoelectric performance (piezoelectric constant d33 of 50 pm/V or more). This parameter optimization prevents the conspicuous decrease in piezoelectric performance that occurs when bismuth ferrite content is too high.
Solution Approach 2:
The patent replicates the successful compositional ratios and processing conditions through detailed specification of manufacturing parameters. By copying the optimal solid solution composition (xBaTiO3-yBiFeO3 with x=0.6-0.8, y=0.1-0.4) and sintering conditions, the invention ensures consistent reproduction of both high Curie temperature and good piezoelectric performance across production batches.
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 material achieves high piezoelectric performance and Curie temperature, enabling applications such as liquid discharge heads, ultrasonic motors, and dust removing devices with performance comparable to or exceeding those using lead-containing materials.
Implementation Method 1
a commonly used piezoelectric material is an ABO3-type perovskite metal oxide such as lead titanate zirconate (hereinafter, referred to as 'PZT')
Data Source
AI summary
Provided is a piezoelectric material that achieves both high piezoelectric performance and high Curie temperature. In addition, provided are a piezoelectric element, a liquid discharge head, an ultrasonic motor, and a dust removing device, which use the piezoelectric material. The piezoelectric material includes a perovskite-type metal oxide that is expressed by the following general formula (1): xBaTiO3-yBiFeO3-zBi(M0.5Ti0.5)O3 (1), where M represents at least one type of element selected from the group consisting of Mg and Ni, x satisfies 0.25≦x≦0.75, y satisfies 0.15≦y≦0.70, z satisfies 0.05≦z≦0.60, and x+y+z=1 is satisfied.