Piezoelectric crystal elements of shear mode and process for the preparation thereof

Abstract

Piezoelectric crystal elements are provided having preferred cut directions that optimize the shear mode piezoelectric properties. In the discovered cut directions, the crystal elements have super-high piezoelectric performance with d 15 , d 24 and d 36 shear modes at room temperature. The d 15 shear mode crystal gives a maximum d value and is free from the cross-talk of d 11 and d 16 . The d 36 mode is extremely reliable compared to other shear elements due to its ready re-poling capability. The crystal elements may be beneficially used for high-sensitive acoustic transducers.

1 . A piezoelectric element, comprising: 
 a PMN-PT structured element wherein: 
 said crystal element includes a cutting direction of xzt−22.5° (±5°) and poling along a <111> pseudo-cubic axis of said crystal element; and  
 said the crystal element having a maximum piezoelectric coefficient d, 5  greater than 5,000 pC/N at room temperature.  
   
   
   
       2 . A piezoelectric element, according to  claim 1 , wherein: 
 said crystal elements are operative in d 15  shear mode and have near zero cross talks resulting from d 16  and d 11  responses during an operation.    
   
   
       3 . A piezoelectric element, comprising: 
 a crystal element having a cutting direction zxt ±45° (±5°) (011-cut) and poling along <011> psedo-cubic axis of said crystal elements; and    said crystal element having a d 36  value up to about 2600 pC/N at room temperature.    
   
   
       4 . A piezoelectric element, according to  claim 3 , wherein: 
 said crystal element are operative in d 36  shear mode; and    said crystal element enables a ready re-polling enabled by a set of external poling electrodes being operative as a set of working electrodes.    
   
   
       5 . A free XY-cut (<111> poling 3 m) PMN-PT crystal element for d 15  mode, comprising: 
 a piezoelectric coefficient d 15  greater than 4,000 pC/N at room temperature, wherein    a d 15  value is independent from a cut direction rotating around a Z-axis.    
   
   
       6 . A Y-cut (<111> poling 3 m) PMN-PT crystal element for d 15  mode , comprising: 
 a d 15  value up to 4000 pC/N, and    said d 15  being substantially free of cross talk from d 16 .    
   
   
       7 . A shear-mode single crystal element having a composition represented by the formula:  
       PbZ y (Mg 1/3 Nb 2/3 ) 1-x-y Ti x O 3    where y is defined as 0 to 0.10;    x is defined as 0.20 to 0.35; and    Z is defined as at least one dopant element.    
   
   
       8 . A shear mode single crystal element, according to  claim 7 , wherein: 
 said at least one dopant element is selected from the group consisting of Zr, Hf, Sn, In, Sc, Tm, Nb, Ta, Zn, Yb, Lu, Sb, Bi, Mn, Ga, Ce, Ni, W, Cu, Fe, K, Na, Li, and Ba.    
   
   
       9 . A process for preparation of at least one single crystal element, comprising the steps of: 
 poling a single crystal in the direction along the <111> cubic axis under a 500 V/mm electrical field at room temperature;    said single crystal being a piezoelectric crystal element with a cutting direction of xzt−22.5° (±5°);    mechanically finishing said single crystal element with cuttings along xzt−22.5°, ±5°;    coating at least one electrode on each of a first and second X surface; and    removing poling electrodes each of a first and second Z surface.    
   
   
       10 . A process for the preparation of at least one single crystal element, comprising the steps of: 
 mechanically finishing said single crystal elements with cuttings along zxt ±45° (±5°);    coating electrodes on a pair of Z surfaces; and    poling said single crystal in the direction along a <011> cubic axis under a 500 V/mm electrical field at room temperature.