Lead-free piezoceramic materials
The present invention relates to lead-free piezoelectric ceramic materials comprising crystalline (and preferably perovskite crystalline) structures of the formula Bi 1-x (RE) x FeO 3 , where RE is one or more of La, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, and 0≦x≦0.3. The materials are at or near the morphotropic phase boundary and display enhanced piezoelectric and dielectric properties.
1. A lead-free piezoelectric ceramic material having the formula:
Bi i-x RE x FeO 3
where Bi is bismuth, Fe is iron, O is oxygen, RE is one or more of: La, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, and wherein:
0.125≦x≦0.3 for La, Pr, Nd, or Pm;
0.125<x≦0.3 for Sm; and
0<x≦0.3 for Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu,
and the composition of said material has an x value that is within 0.010 of the x value of the morphotropic phase boundary of such material.
2. The lead-free piezoelectric ceramic material of claim 1 , wherein RE is Sm.
3. The lead-free piezoelectric ceramic material of claim 2 , wherein 0.13<x≦0.15.
4. The lead-free piezoelectric ceramic material of claim 1 , wherein said compound has an x value that is within 0.005 of the x value of the morphotropic phase boundary of such material.
5. The lead-free piezoelectric ceramic material of claim 4 , wherein said compound has an x value that is within 0.002 of the x value of the morphotropic phase boundary of such material.
6. A device capable of generating a mechanical force in response to a change in an electric field, wherein said device contains a lead-free piezoelectric ceramic material having the formula:
Bi 1-x RE x FeO 3
where Bi is bismuth, Fe is iron, O is oxygen, RE is one or more of: La, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, and wherein:
0.125≦x≦0.3 for La, Pr, Nd, or Pm;
0.125<x≦0.3 for Sm; and
0<x≦0.3 for Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu,
and the composition of said material has an x value that is within 0.010 of the x value of the morphotropic phase boundary of such material,
and wherein said response is a piezoresponse.
7. The device of claim 6 , wherein RE is Sm.
8. The device of claim 7 , wherein 0.13<x≦0.15.
9. The device of claim 6 , wherein said compound has an x value that is within 0.002 of the x value of the morphotropic phase boundary of such material.
10. The device of claim 6 , wherein said device is selected from the group consisting of: a piezoelectric motor, a piezoelectric relay; a piezoelectric speaker; a piezoelectric sensor; a piezoelectric ultrasound sonic generator; and a piezoelectric pump.
11. A device capable of generating a change in an electric field in response to a mechanical force, wherein said device contains a lead-free piezoelectric ceramic material having the formula:
Bi 1-x RE x FeO 3
where Bi is bismuth, Fe is iron, O is oxygen, RE is one or more of: La, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, and wherein:
0.125≦x≦0.3 for La, Pr, Nd, or Pm;
0.125<x≦0.3 for Sm; and
0<x≦0.3 for Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu;
and the composition of said material has an x value that is within 0.010 of the x value of the morphotropic phase boundary of such material,
and wherein said response is a piezoresponse.
12. The device of claim 11 , wherein RE is Sm.
13. The device of claim 12 , wherein 0.13<x≦0.15.
14. The device of claim 11 , wherein said compound has an x value that is within 0.002 of the x value of the morphotropic phase boundary of such material.
15. The device of claim 11 , wherein said device is selected from the group consisting of: a piezoelectric sensor, a piezoelectric battery, a piezoelectric transducer, and a piezoelectric microphone.