High frequency piezoelectric crystal composites, devices, and methods for manufacturing the same
Inventors
Han, Pengdi • Tian, Jian • Meneou, Kevin • Stone, Brandon
Assignees
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Publication Number
US-10230040-B2
Publication Date
2019-03-12
Expiration Date
Abstract
The present invention generally relates to high frequency piezoelectric crystal composites, devices, and method for manufacturing the same. In adaptive embodiments an improved imaging device, particularly a medical imaging device or a distance imaging device, for high frequency (>20 MHz) applications involving an imaging transducer assembly is coupled to a signal imagery processor. Additionally, the proposed invention presents a system for photolithography based micro-machined piezoelectric crystal composites and their uses resulting in improved performance parameters.
Core Innovation
A piezoelectric PMN-PT based crystal composite is described with a crystal composition represented by a formula including Pb(B’1/2B’’1/2)O3−y·PbTiO3−(1−x−y)·Pb(Mg1/3Nb2/3)O3, where x and y are molar % values each defined as 0.00 to 0.50. The composite further defines B’ as Indium (In), Ytterbium (Yb), Scandium (Sc), Zirconium (Zr), or Iron (Fe), and B’’ as Niobium (Nb) or Tantalum (Ta).
The document focuses on a high-frequency piezoelectric PMN-PT based crystal composite system operating at greater than 20 MHz and described as enabling operation up to 100+ MHz. The composite system targets thickness electromechanical coupling k_t in a range of 0.65–0.90 and is directed to improving bandwidth, axial resolution, and imaging depth for ultrasound imaging.
Fabrication is described using photolithography-based micromachining with deep reactive ion etching to form kerfs and a hybrid discontinuous post array structure, including 1-3 hybrid and related 2-2/1-3 discontinuous post arrays. The composite also addresses detrimental lateral epoxy clamping effects by selecting crystal cuts and poling directions, including (001)<001> and (011)<011>, with kerf or polymer fill line orientations about ±32.5° (+/−22.5°) away from specified crystallographic directions.
Claims Coverage
The independent claims define a piezoelectric PMN-PT based crystal composite by a specific crystal-composition formula with defined molar % ranges and element selections. The claim set further includes performance constraints, a medical imaging device for operative ultrasound imaging, and a crystal cut/poling configuration with zero-strain direction behavior.
Compositional formula for PMN-PT crystal composite
A piezoelectric PMN-PT based crystal composite having a crystal composition represented by the formula x*Pb(B’1/2B’’1/2)O3−y*PbTiO3−(1−x−y)*Pb(Mg1/3Nb2/3)O3, wherein x and y are each 0.00 to 0.50 molar %, B’ is Indium (In), Ytterbium (Yb), Scandium (Sc), Zirconium (Zr), or Iron (Fe), and B’’ is Niobium (Nb) or Tantalum (Ta).
Thickness electromechanical coupling range
A piezoelectric crystal composite having a thickness electromechanical coupling factor (k_t) in the range of about 0.65 to 0.90.
High-frequency operability threshold
A piezoelectric crystal composite that is operable at a frequency of at least 80 MHz.
Medical imaging device for operative ultrasound imaging
A piezoelectric crystal composite, in combination with a medical imaging device configured for operative ultrasound imaging.
Crystal cut and poling for zero-strain direction
A piezoelectric crystal composite that is (001) cut and <011> poled such that it provides zero strain in the direction +/-2.5° away from the <011> direction, using the coordinate rotation d31 relationship.
Across the independent claims, the main inventive elements are the specified PMN-PT composition formula with defined molar % ranges and element choices, together with quantitative performance constraints, use in a medical imaging device for operative ultrasound imaging, and a specific crystal cut/poling configuration that provides a zero-strain direction defined via a coordinate-rotation d31 relationship.
Stated Advantages
Enables operation up to 100+ MHz.
Achieves thickness electromechanical coupling k_t of 0.65–0.90.
Improves bandwidth and axial resolution.
Improves imaging depth.
Reduces detrimental lateral epoxy clamping effects by selecting crystal cuts/poling and kerf or polymer fill line orientation to provide strain-free directions.
Documented Applications
Medical ultrasound imaging using a medical imaging device configured for operative ultrasound imaging, including dermatology, ophthalmology, laparoscopy, intracardiac, intravascular, intracranial, and intra-cavity/intra-luminal ultrasound.
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