Piezoceramic lead-free material

Abstract

The invention relates to a piezoelectric lead-free material based on bismuth sodium titanate, to a method for the production thereof, and to the use thereof.

Claims

1. A method for producing a piezoceramic lead-free bismuth sodium titanate comprising the steps of: mixing and grinding sodium bismuthate and a titanium source in water to form a mixture; and sintering the mixture to form the piezoceramic lead-free bismuth sodium titanate; wherein the piezoceramic lead-free bismuth sodium titanate consists of formula Bi.sub.0.5Na.sub.0.5TiO.sub.3.

2. The method of claim 1, wherein the aqueous system comprises water.

3. A method according to claim 1, wherein the sintering takes place in an oxygen-rich environment which prevents, minimizes, or in any case significantly reduces, the development of oxygen vacancies.

4. A method for producing a piezoceramic lead-free bismuth sodium titanate comprising the steps of: mixing and grinding sodium bismuthate with a titanium source in an aqueous system to form a mixture; and sintering said mixture to form the piezoceramic lead-free bismuth sodium titanate; wherein said aqueous system comprises water and does not contain an explosive material; and wherein the piezoceramic lead-free bismuth sodium titanate consists of formula Bi.sub.0.5Na.sub.0.5TiO.sub.3.

5. The method of claim 4, wherein the explosive material is ethanol.

6. A method according to claim 4, wherein the sintering takes place in an oxygen-rich environment which prevents, minimizes, or in any case significantly reduces, the development of oxygen vacancies.

7. A method for producing a piezoceramic material comprising the steps of: mixing and grinding sodium bismuthate with a titanium source in an aqueous system to form a mixture; and sintering said mixture to form the piezoceramic material; wherein said aqueous system comprises water and does not contain an explosive material; wherein the piezoceramic material has a lead content below 0.1-mass-%; and wherein the piezoceramic material consists of formula Bi.sub.0.5Na.sub.0.5TiO.sub.3.

8. A method according to claim 7, wherein the sintering takes place in an oxygen-rich environment which prevents, minimizes, or in any case significantly reduces, the development of oxygen vacancies.

Description

DETAILED DESCRIPTION

(1) Accordingly, a method according to the invention provides for the production of a piezoceramic lead-free material composed of bismuth sodium titanate, sodium bismuthate (NaBiO.sub.3) being used as the sodium and bismuth source.

(2) A stoichiometric compound is present in the Bi.sub.0.5.sup.3+Na.sub.0.5.sup.1+Ti.sup.4+O.sub.3.sup.2 (BNT) system. Oxygen vacancies may be created by foreign substances, i.e., impurities, or also by the calcination and sintering processes. This is prevented by the use of Na.sup.1+Bi.sup.5+O.sub.3.sup.2. In this compound, the oxygen concentration is higher compared to BNT, and is liberated during sintering due to the reduction of Bi.sup.5+ to Bi.sup.3+.

(3) Thus, the sintering advantageously takes place in an oxygen-rich environment which prevents/minimizes, or in any case significantly reduces, the development of oxygen vacancies.

(4) As a result, the sintering temperature may be lowered by as much as 50 C. A farther distance from the melting temperature, which may be approximately 1250 C., is thus provided. The method is therefore also more energy-efficient as the result of lowering the process temperature.

(5) According to one preferred refinement of the invention, the precursors of the piezoceramic material is mixed and ground in an aqueous system. This has the advantage that requirements for working with explosive materials do not apply, since ethanol is not used as solvent.

(6) Environmental standards concerning the lead content of PZT ceramics also do not apply due to the fact that the lead content is minimized; the content of lead is particularly preferably below 0.1 mass-%.

(7) A piezoceramic lead-free material according to the invention may be used, for example, in the area of sensors, in particular for measuring forces, accelerations, and pressures, and in the area of actuators, in particular positioning technology and ultrasound generation.