Research and development of lead-free piezoelectric materials are presently the hottest topics in the field of piezoelectricity. Also a huge advantage of PZT and related systems, is that this one family, with minor modifications, is suitable for nearly all applications.
Environmental and health issues related to Pb-based materials are obvious. According to RoHS, any homogeneous component containing more than 0.1 weight % of lead is subjected to restrictions ; and hence, the fact that the best piezoelectric materials contain lead up to 60 weight %, may in the future, seriously hamper their use in everyday applications.
my question is that "why people looking for replacement for PZT ( lead zirconat titanate ) which contain Pb up to 60% of weight because Pb is considered toxic or dangerous for life . While the alternative lead free piezoelectric KNN, BNT , BNN , BST , BT , BZT , all these alternatives also might contain toxic or hazard element for example Barium is toxic and dangerous for environment "
Why people want to replace lead? The alternative are toxic also? so why the replacement of hazard element with another hazard one ?
Content of lead in one film is not so dangerous, but dangerous is production of lead-containing ceramics and films due to PbO evaporation into the atmosphere.
Barium is less toxic but also not envirometally friendly element.
Niobate ferroelectrics is good alternative, but they are much more expensive ...
@Yu. I. Yuzyuk
The Restriction of Hazardous Substances Directive( RoHS ) considered any homogeneous component containing more than 0.1 weight % of lead is subjected to restrictions ( because more than 0.1 % is dangerous for the environment and hazard )
but the alternative ( for example one of the alternative is BCT-BZT " (Ba,Ca)TiO3-Ba(Zr,Ti)O3 " ) contain Barium .
Barium compound also consider dangerous and hazard for environment .
Now , why the replacement of PZT ( the best piezoelectric material for different application like actuator , Detector , Sonar senser , Energy harvester ) with another alternative material ( KNN , BNT , BCT-BZT , etc. ) which are also either hazard for environment or much more expansive than PZT .
You can see our publication (see attached file) to estimate some piezoelectric properties of rocks and minerals.
PZT is indeed frequently prepared by reaction of individual oxides at high temperature, among them PbO. As the latter is indeed volatile, as mentioned in the first answer, an excess has to be introduced as part of the PbO is lost. This is indeed a serious problem. The other compounds present in PZT are not so easily leached in solution nor are volatile as PbO is.
Alain
@Alain Celzard
as i mentioned "(According to RoHS, any homogeneous component containing more than 0.1 weight % of lead is subjected to restrictions ; and hence, the fact that the best piezoelectric materials contain lead up to 60 weight %, may in the future, seriously hamper their use in everyday applications.)"
The problem is not in manufacturing or preparation but the problem is in marketing of this product .
Also the problem is after marketing so the RoHS put restriction
also the problem of recycling .
And one can solve the problem of generation of PbO at the preparation of PZT by using ventilation or evacuated room to prevent the diffusion of PbO to the environment .
Is there any other reasons to PZT from microwave applications? What about the microwave loss of PZT?
Piezoelectric materials based on lead have held several applications such as automobiles, microphones, sonar, resonators, medical imaging/diagnostics, printers, ultrasonic motors, wearable devices, smart structures, medical implants, etc.) for over 50 years. The dominance of PZT-based ceramics is due to their superior piezoelectric response, which ultimately ensures an unmatched efficiency in the direct interconversion of electrical and mechanical energy. Beyond this superior piezoelectric response, lies a level of toxicity that threatens the position of PZT as the leading piezoelectric ceramic, and has sparked urgent global efforts to identify environmentally benign substitutes. A fundamental issue that emerges with the recognition of lead toxicity is the need to find surrogate materials in the myriad of products in which PZT plays a major functional role. Potassium sodium niobate (K x Na1−x NbO3 or KNN hereafter) is a potential Pb-free replacement for PZT, and for room temperature applications, in particular, looks promising. Material replacement in existing products has many obstacles, such as substitution costs, price ratio, and in some instance the end user's propensity to change. Consequently, for material substitution to be viable: (i) the benefit of implementing a novel and untested material must be worth the risk of abandoning the well-established current materials; (ii) the cost of substitution must not exceed the overall benefits; (iii) the costs of renovating production equipment and processes is acceptable; (iv) the implications of substitution are manageable in a wider systems context; and (v) institutional, legal, social, and environmental consequences can be overcome.
For more information, you can read this article.
Ibn-Mohammed, T., et al. "Are lead-free piezoelectrics more environmentally friendly?." MRS Communications 7.1 (2017): 1-7.
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