Piezoelectric transducer, manufacturing process pertaining thereto, and resonant ultrasound spectroscopy device

Patent metadata

Field	Value
Publication number	US-10859537-B2
Application number	US-201716341491-A
Country	US
Kind code	B2
Filing date	Sep 21, 2017
Priority date	Oct 13, 2016
Publication date	Dec 8, 2020
Grant date	Dec 8, 2020

Abstract

Disclosed is a piezoelectric transducer of the type including a stack of a contact piece, a piezoelectric pellet and a support of very great stiffness. Specifically, the contact piece forms tips, the respective apex of which constitutes contact points that are spatially isolated from one another. Also disclosed is a process for the manufacture of such a contact piece as well as a resonant ultrasound spectroscopy device including one or more of such piezoelectric transducers.

First claim

The invention claimed is:

1. A piezoelectric transducer ( 9 , 9 a , 9 b ) comprising:
a piezoelectric pellet ( 2 ); and
a contact piece ( 1 ) stacked on the piezoelectric pellet ( 2 ),
wherein the contact piece ( 1 ) forms tips ( 10 ),
the respective apex of the tips ( 10 ) constituting contact points ( 11 ) spatially isolated from one another, and
wherein the contact piece is arranged in order to establish a mechanical contact, by at least one of the contact points ( 11 ), with a sample (E 1 ) to be analyzed,
wherein the contact points ( 11 ) are distributed over a convex surface (S 1 ).

2. The piezoelectric transducer according to claim 1 , wherein the tips ( 10 ) have a height (D 2 ) comprised between 1 μm and 10 mm.

3. The piezoelectric transducer according to claim 1 , wherein the contact points ( 11 ) are regularly spaced apart with a pitch (D 1 ) comprised between 1 μm and 10 mm.

4. The piezoelectric transducer according to claim 1 , wherein the contact piece ( 1 ) is made from a material the ratio √{square root over (E c )}/d c of which is greater than 1 GPa 1/2 *cm 3 /g, with E c the Young's modulus and d c , the density of this material.

5. The piezoelectric transducer according to claim 1 , wherein the contact piece ( 1 ) comprises or consists of polycrystalline diamond and/or polycrystalline cubic boron nitride and/or beryllium and/or aluminium and/or magnesium.

6. The piezoelectric transducer according to claim 1 , wherein, in a transverse plane, the contact piece ( 1 ) forms a radially truncated disk.

7. The piezoelectric transducer according to claim 1 , further comprising a support ( 3 , 3 b ) and wherein the piezoelectric pellet ( 2 ) is mounted between the support ( 3 , 3 b ) and the contact piece ( 1 ).

8. The piezoelectric transducer according to claim 7 , wherein the support ( 3 , 3 b ) is made from a material the ratio √{square root over (E s )}/d s of which is greater than 3 GPa 1/2 *cm 3 /g, with E s the Young's modulus and d s , the density of this material.

9. The piezoelectric transducer according to claim 7 , wherein the support ( 3 , 3 b ) comprises or consists of polycrystalline diamond and/or polycrystalline cubic boron nitride and/or beryllium and/or silicon carbide and/or aluminium.

10. The piezoelectric transducer according to claim 7 , wherein the support ( 3 ) is axisymmetric.

11. The piezoelectric transducer according to claim 10 , wherein the support ( 3 ) is a cylindrical support ( 3 ) and the cylindrical support ( 3 ) has a ratio h/d s comprised between 0.3 and 2, with h the height and d s the diameter of this cylindrical support.

12. The piezoelectric transducer according to claim 10 , wherein the support ( 3 , 3 b ) is a sphere ( 3 b ) truncated axially so as to form a mounting surface, and wherein the piezoelectric pellet ( 2 ) is mounted on the mounting surface.

13. The piezoelectric transducer according to claim 7 , further comprising:
a bearing element ( 7 , 7 a , 7 b ), and
one or more positioning elements ( 41 , 42 , 43 ),
this or these positioning elements ( 41 , 42 , 43 ) linking the support and the bearing element ( 7 , 7 a , 7 b ) and being made from a material the stiffness of which is less than 200 Mpa.

14. The piezoelectric transducer according to claim 13 , wherein the positioning element(s) ( 41 , 42 , 43 ) is (are) arranged in order to filter the frequencies of acoustic waves greater than 5 kHz.

15. The piezoelectric transducer according to claim 1 , wherein the piezoelectric transducer is arranged in order to transmit or receive acoustic waves having frequencies comprised between 5 kHz and 1 Mhz.

16. The piezoelectric transducer according to claim 1 , wherein the contact piece ( 1 ) comprises at least nine tips ( 10 ).

17. A resonant ultrasound spectroscopy device comprising at least one piezoelectric transducer ( 9 , 9 a , 9 b ) according to claim 1 .

18. The resonant ultrasound spectroscopy device according to claim 17 , comprising two of the piezoelectric transducers ( 9 a , 9 b ), wherein the directions in which the tips of one ( 9 a ) of said piezoelectric transducers extend are:
parallel, or
intersect with the directions in which the tips of the other ( 9 b ) one of said two piezoelectric transducers extend, the points of intersection of said directions being situated in the direction in which the tips extend from their base to the contact points.

19. A piezoelectric transducer ( 9 , 9 a , 9 b ) comprising:
a piezoelectric pellet ( 2 ); and
a contact piece ( 1 ) stacked on the piezoelectric pellet ( 2 ),
wherein the contact piece ( 1 ) forms tips ( 10 ),
the respective apex of the tips ( 10 ) constituting contact points ( 11 ) spatially isolated from one another,
wherein the contact piece is arranged in order to establish a mechanical contact, by at least one of the contact points ( 11 ), with a sample (E 1 ) to be analyzed, and
wherein the contact points ( 11 ) are distributed such that no geometrical plane passes less than 0.5 μm from more than three of said contact points.

20. A process for the manufacture of a contact piece ( 1 ) for a piezoelectric transducer ( 9 , 9 a , 9 b ) comprising a piezoelectric pellet ( 2 ) and a contact piece ( 1 ) stacked on the piezoelectric pellet ( 2 ), wherein the contact piece ( 1 ) forms tips ( 10 ), the respective apex of the tips ( 10 ) constituting contact points ( 11 ) spatially isolated from one another, and wherein the contact piece is arranged in order to establish a mechanical contact, by at least one of the contact points ( 11 ), with a sample (E 1 ) to be analyzed, the process comprising a step of machining the tips ( 10 ) by wire electrical discharge machining.

21. The process according to claim 20 , wherein the step of machining the tips ( 10 ) comprises:
a first series of lines cut by electroerosion of the contact piece ( 1 ), parallel to a first axis of erosion,
a second series of lines cut by electroerosion of the contact piece ( 1 ), parallel to a second axis of erosion,
the first axis of erosion not being parallel to the second axis of erosion.

Assignees

• Univ Sorbonne
• Centre Nat Rech Scient
• Inst Nat Sante Rech Med

Inventors

• Dargent Pascal
• Grimal Quentin

Classifications

• G01N2291/265

  Spherical objects · CPC title

• G01N2291/269

  Various geometry objects · CPC title

• G01H13/00

  Measuring resonant frequency · CPC title

• G01N29/28

  providing acoustic coupling {, e.g. water (impedance matching G10K11/02)} · CPC title

• G01N2203/0075

  Strain-stress relations or elastic constants · CPC title