<P> In contrast, Japanese manufacturers shared their information, quickly overcoming technical and manufacturing challenges and creating new markets . In Japan, a temperature stable crystal cut was developed by Issac Koga . Japanese efforts in materials research created piezoceramic materials competitive to the United States materials but free of expensive patent restrictions . Major Japanese piezoelectric developments included new designs of piezoceramic filters for radios and televisions, piezo buzzers and audio transducers that can connect directly to electronic circuits, and the piezoelectric igniter, which generates sparks for small engine ignition systems and gas - grill lighters, by compressing a ceramic disc . Ultrasonic transducers that transmit sound waves through air had existed for quite some time but first saw major commercial use in early television remote controls . These transducers now are mounted on several car models as an echolocation device, helping the driver determine the distance from the car to any objects that may be in its path . </P> <P> The nature of the piezoelectric effect is closely related to the occurrence of electric dipole moments in solids . The latter may either be induced for ions on crystal lattice sites with asymmetric charge surroundings (as in BaTiO and PZTs) or may directly be carried by molecular groups (as in cane sugar). The dipole density or polarization (dimensionality (C m / m)) may easily be calculated for crystals by summing up the dipole moments per volume of the crystallographic unit cell . As every dipole is a vector, the dipole density P is a vector field . Dipoles near each other tend to be aligned in regions called Weiss domains . The domains are usually randomly oriented, but can be aligned using the process of poling (not the same as magnetic poling), a process by which a strong electric field is applied across the material, usually at elevated temperatures . Not all piezoelectric materials can be poled . </P> <P> Of decisive importance for the piezoelectric effect is the change of polarization P when applying a mechanical stress . This might either be caused by a reconfiguration of the dipole - inducing surrounding or by re-orientation of molecular dipole moments under the influence of the external stress . Piezoelectricity may then manifest in a variation of the polarization strength, its direction or both, with the details depending on: 1 . the orientation of P within the crystal; 2 . crystal symmetry; and 3 . the applied mechanical stress . The change in P appears as a variation of surface charge density upon the crystal faces, i.e. as a variation of the electric field extending between the faces caused by a change in dipole density in the bulk . For example, a 1 cm cube of quartz with 2 kN (500 lbf) of correctly applied force can produce a voltage of 12500 V . </P> <P> Piezoelectric materials also show the opposite effect, called the converse piezoelectric effect, where the application of an electrical field creates mechanical deformation in the crystal . </P>

A piezoelectric crystal undergoes what process when under physical strain