Piezoelectric Actuator Phase Transition Strain Saturation
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Solution Overview
Problem
Conventional piezoelectric devices face limitations in achieving significant strain due to their design, particularly when thickness is reduced, as they rely solely on the piezoelectric effect, leading to insufficient performance in applications like inkjet recording heads where increased electric field strength results in reduced strain and saturated output.
Innovation Solution
A piezoelectric device with a monocrystalline film of an inorganic crystalline compound that undergoes phase transition from a first ferroelectric crystal to a second ferroelectric crystal under specific electric field conditions, utilizing both the piezoelectric effect and crystal structure change to achieve greater strain, with the electric field strengths optimized to ensure stable phase transition and enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thickness of the piezoelectric body is reduced to decrease device size, then the device size is reduced, but the electric field strength increases excessively causing the piezoelectric effect to saturate and strain magnitude to decrease
Solution Approach 1:
The patent changes the crystal structure parameter of the piezoelectric body from a conventional perovskite structure to a tungsten bronze structure. This structural parameter change enables the material to maintain high piezoelectric performance even under high electric field conditions, preventing saturation. The tungsten bronze structure's unique atomic arrangement allows for greater ion displacement and higher strain output despite the increased electric field strength caused by reduced thickness.
Solution Approach 2:
The patent employs a composite approach by combining the tungsten bronze crystal structure with specific compositional elements (such as Pb1-xLaxZr1-yTiyO3 system with specific x and y ratios). This composite material design creates a piezoelectric body that leverages both the structural advantages of tungsten bronze and the compositional tuning to optimize piezoelectric coefficients, achieving high strain output in thin-film configurations.
2Device complexity
If only the conventional piezoelectric effect is utilized to simplify device design, then the device design is simplified, but the strain magnitude is limited and cannot meet increasing demands
Solution Approach 1:
The patent fundamentally changes the material parameter from conventional perovskite to tungsten bronze crystal structure. This parameter change enables the material to exhibit enhanced piezoelectric coefficients and higher strain capacity. The tungsten bronze structure's distorted octahedral framework and off-center cation positions create stronger piezoelectric response, allowing the device to achieve greater strain without adding operational complexity.
3Manufacturing precision
If the electric field strength is increased to compensate for reduced piezoelectric performance in thin devices, then the performance is maintained, but the device cannot operate beyond the saturation point Ex
Solution Approach 1:
The patent changes the material's intrinsic parameters by adopting the tungsten bronze crystal structure, which has higher piezoelectric coefficients and different electro-mechanical coupling characteristics. This parameter change shifts the saturation point to higher electric field strengths and extends the linear operating range. The material can now operate effectively at electric field strengths above the conventional Ex limit while maintaining proportional strain response.
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 device achieves stable and significant strain across various electric field ranges, effectively addressing the limitations of conventional devices by leveraging both piezoelectric and structural changes, even when thickness is reduced, thereby improving performance in applications like inkjet recording heads.
Implementation Method 1
phase transition of at least a portion of the first ferroelectric crystal to a second ferroelectric crystal occurs when the strength of the electric field is at or above a predetermined level E1
Implementation Method 2
the piezoelectric body expands and contracts according to increase and decrease in the strength of an electric field applied from the electrodes to the piezoelectric body along a predetermined direction
Data Source
AI summary
A piezoelectric device constituted by a piezoelectric body and electrodes. The piezoelectric body is a monocrystalline piezoelectric film formed, above a substrate, of an inorganic crystalline compound containing a first ferroelectric crystal when no electric field is applied to the piezoelectric film, and having a characteristic that phase transition of at least a portion of the first ferroelectric crystal to a second ferroelectric crystal occurs when the electric field strength applied to the piezoelectric film is at or above a predetermined level E1, the first and second ferroelectric crystals correspond to different crystal systems, and the piezoelectric device is driven under a condition that the minimum strength Emin, the maximum strength Emax, and the predetermined level E1 of the applied electric field satisfy the inequalities, Emin<E1<Emax.