Compositions for high power piezoelectric ceramics
Piezoelectric compositions of the formula Pb (1-z) M z (Mg 1/3 Nb 2/3 ) x (Zr y Ti 1-y ) 1-x O 3 where M can be either Sr or Ba or both, x is between about 0.35 and about 0.40, y is between about 0.36 and about 0.42, and z is between about 0.04 and about 0.08. The piezoelectric ceramic is provided as a composite perovskite structure. Additional materials or dopants can be added to the piezoelectric ceramic of the present invention. Example of dopants that can be added to the piezoelectric ceramic include, but are not limited to: MnO 2 , Ni 2 O 3 , TeO 3 , TeO2, MoO 3 , Nb 2 O 5 , Ta 2 O 5 , CoCO 3 , and Y 2 O 3 . The piezoelectric ceramics of the present invention can be used to fabricate piezoelectric elements for a wide variety of devices that can be fabricated to exhibit high power applications including miniaturized displacement elements, buzzers, transducers, ultrasonic sensors and ultrasonic generators, and the like.
1. A piezoelectric ceramic composition made by combining Pb, Sr, Ba, Mg, Nb, Zr, and Ti, precursor materials according to the base formula:
Pb (1-z) M z (Mg 1/3 Nb 2/3 ) x (Zr y Ti 1-y ) 1-x O 3
wherein M is selected to be either Sr or Ba, x is between about 0.35 and about 0.40, y is between about 0.36 and about 0.42, and z is between about 0.04 and about 0.08;
wherein said composition additionally includes a MnO 2 dopant in an amount between 0.2 wt% and 0.4 wt%.
and further wherein said composition additionally comprises between about 0.01 and 2.0 wt % Nb 2 O 5 as a dopant.
2. A composition according to claim 1 where x is between 0.37 and 0.38, y is between 0.38 and about 0.39, and z is between 0.05 and 0.07.
3. A composition according to claim 1 , wherein said composition additionally comprises one or more additional dopants provided by adding one or more dopant precursors selected from the group consisting of: Fe 2 O 3 , CeO 2 , Sb 2 O 3 , Sm 2 O 3 , CuO, CdO, Ti 2 O 3 , MoO 3 , Nd 2 O 3 , Yb 2 O 3 , Ta 2 O 5 , Y 2 O 3 , In 2 O 3 , Tm 2 O 3 , RuO 2 , Ni 2 O 3 , TeO 2 , and CoCO 3 , and mixtures thereof.
4. The composition of claim 1 wherein M is Ba.
5. The composition of claim 1 wherein M is Sr.
6. A piezoelectric element comprising a composition according to claim 1 and having at least two electrodes formed thereon.
7. A composition according to claim 1 , wherein said composition has a mechanical quality factor Q m of between about 900 and about 2000.
8. A composition according to claim 1 , wherein said composition has a relative permittivity (∈) of between about 2000 and about 4000 F/m.
9. A composition according to claim 1 , wherein said composition has a piezoelectric strain constant (d 33 ) of between about 250 and about 500 PC/N.