Piezoelectric Element Stress Control via Orientation Layer
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Solution Overview
Problem
Piezoelectric elements in liquid ejection heads experience internal stress accumulation and cracking due to temperature during the formation of the piezoelectric layer, particularly in complex oxides like potassium, sodium, and niobium-based materials.
Innovation Solution
A piezoelectric element design incorporating a piezoelectric layer with a perovskite structure containing potassium, sodium, and niobium, where X-ray diffraction is used to measure asymmetric reflection, separating peaks to determine lattice constants, and ensuring a slope of less than 0.002 in the approximate straight line to minimize tensile stress, and includes an orientation control layer with bismuth, iron, and titanium to control orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a piezoelectric layer made of perovskite type complex oxide containing potassium, sodium, and niobium is formed at high temperature, then the piezoelectric properties are improved, but internal stress accumulates and cracks occur in the layer
Solution Approach 1:
The patent applies parameter changes by precisely controlling the oxygen partial pressure (10^-5 to 10^-2 Pa) and temperature (600-800°C) during the formation process of the piezoelectric layer. This controlled parameter approach allows the layer to achieve desired piezoelectric properties while minimizing internal stress and preventing cracks, thus resolving the contradiction between improving piezoelectric properties and maintaining layer integrity.
Solution Approach 2:
The patent implements local quality by creating an orientation control layer with specific crystal orientation (c-axis perpendicular to substrate) that serves as a template for the piezoelectric layer. This localized structural control in the orientation layer propagates to the piezoelectric layer, enabling it to achieve good piezoelectric properties without accumulating excessive internal stress, thereby resolving the contradiction between layer strength and piezoelectric performance.
2Power
If the piezoelectric layer is made thicker to improve performance, then the piezoelectric effect is enhanced, but internal stress causes cracking in the layer
Solution Approach 1:
The patent uses parameter changes by controlling the formation temperature (600-800°C) and oxygen partial pressure (10^-5 to 10^-2 Pa) to enable the formation of thicker piezoelectric layers without crack formation. These optimized parameters allow stress management during layer growth, permitting increased thickness for enhanced piezoelectric effect while maintaining layer integrity.
Solution Approach 2:
The patent applies preliminary action by first forming an orientation control layer with proper crystal orientation before depositing the piezoelectric layer. This preliminary structural preparation ensures that subsequent piezoelectric layer growth proceeds with controlled stress distribution, enabling thicker layers to be formed without cracking while maintaining good piezoelectric properties.
3Manufacturing precision
If the piezoelectric layer is formed at high temperature to achieve good crystal structure, then the piezoelectric properties are improved, but tensile stress increases causing cracks
Solution Approach 1:
The patent resolves this contradiction by changing the formation parameters to a specific temperature range (600-800°C) and oxygen partial pressure (10^-5 to 10^-2 Pa). This optimized parameter combination enables the piezoelectric layer to develop good crystal structure with reduced tensile stress, preventing crack formation while achieving desired piezoelectric properties.
Solution Approach 2:
The patent uses an orientation control layer as an intermediary between the substrate and the piezoelectric layer. This intermediate layer with controlled crystal orientation (c-axis perpendicular to substrate) serves as a stress buffer and template, allowing the piezoelectric layer to form with good crystal structure at lower temperatures (600-800°C) without accumulating excessive tensile stress that would cause cracking.
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
Reduces tensile stress and minimizes cracking in the piezoelectric layer, enabling thicker layers without defects, thereby enhancing the reliability and durability of the piezoelectric element.
Implementation Method 1
a piezoelectric element provided with a first electrode and a second electrode, and a piezoelectric layer including a plurality of layers containing a complex oxide having a perovskite type structure containing potassium, sodium, and niobium
Implementation Method 2
an X-ray diffraction method is used to measure asymmetric reflection of the piezoelectric layer in a range in which sin2Ψ is 0 or more and 0.7 or less
Data Source
AI summary
A piezoelectric element includes: a first electrode; a second electrode; and a piezoelectric layer provided between the first electrode and the second electrode and including a plurality of layers containing a complex oxide having a perovskite type structure containing potassium, sodium, and niobium, in which an X-ray diffraction method is used to measure asymmetric reflection of the piezoelectric layer in a range in which sin2Ψ is 0 or more and 0.7 or less, Ψ being a tilt angle, an obtained peak is separated into a high-angle-side peak and a low-angle-side peak, a lattice constant in a thickness direction of the piezoelectric layer is obtained based on the low-angle-side peak, and in a case where a plurality of the lattice constants are plotted for the range, when a plurality of plots are linearly approximated by a least squares method, a slope of an approximate straight line is 0.002 or less.