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Abstract
The main characteristics of ferroelectric compositions well suited to power transducers are:
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—a high value of the figure of merit Mo = (d33 /sE 33)2
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—very weak dielectric and mechanical losses under low and high electric field level.
The materials generally used are PZT compositions with oxygen vacancies produced by a lower valenced ions substitution in B cationic site.
The new PZT compositions we have developed are based on:
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—firstly a double substitution on B site with multivalenced ions such as
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—secondly a substitution of manganese ion.
The electromechanical characteristics of these materials are given and compared with standard “hard” piezoceramics:
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—the dielectric permittivity and the figure of merit are increased
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—the internal dielectric field is decreased
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—the mechanical losses are unchanged or weaker
An interpretation is given taking into account a compensation of the change of the oxidation state of manganese during cooling by a change of the valency of the substituted ions.