A SIMPLE APPROACH TO UNDERSTAND SOLID STATE CHEMISTRY WITH THE EXAMPLE OF A PIEZOELECTRIC MATERIAL INCORPORATED IN A BIRTHDAY CARD SPEAKER

Advanced solid materials are present in a large quantity of fields of our quotidian live. All the electronic devices surrounding us, such as mobile phones, computers or appliances are made up of many different materials: ceramics, metals, polymers, etc. The recent development of advanced ceramic materials to be applied in electronic devices, which require high performances as well as relatively economic syntheses and environmentally friendly characteristics, is a wide field in Materials Chemistry. It is important to motivate students to this area, so that, they can understand the importance of the chemistry and the material science in our society. In the present contribution, we would like to relate our experience giving a comprehensive laboratory sessions intended for all undergraduate chemistry students.

Piezoelectric compounds can be defined as materials that produce some electric charge when a mechanical stress is applied (direct effect) or suffer a mechanical deformation when an electric field is applied (reverse effect). These materials are used in several devices such as lighters, speakers, sensors or sonars. Lead zirconate titanate [Pb(Ti1-x,Zrx)O3] (PZT) is the most studied and commercialized ceramic piezoelectric material due to their excellent characteristics. Relation between structure-composition-properties of this material and its easy preparation makes it suitable to use in low value added devices.

In this work, we propose an example for understanding this technology based on the components of a speaker of a musical birthday card, in particular the piezoelectric component, including the chemistry that is involved in these types of devices. Two common characterization techniques in Solid State chemistry are also introduced to the students: X-Ray Diffraction and Electronic Microscopy. Moreover, the discovery by the students of the presence of this type of material in this simple device offers a possibility to motivate them to learn these sciences, and allow them to know the importance of the Solid State Chemistry and the Materials Science in our society.

Different educational methodologies may be used to study and understand these materials with piezoelectric properties. Problem Based Learning (PBL) is a widely applied approach intended to encourage students to learn through the structured exploration of a research problem. Currently this particular system has become a valid teaching method in high schools, where students are encouraged to develop a real research project. The PBL methodology used in this work represents an improvement in the content of the knowledge while simultaneously it fosters the development of communication, problem-solving, and self-directed learning skills.

This work can also be interesting for teachers of inorganic chemistry and material science and undergraduate students owing to its pedagogical character.