Piezo what? It sounds like a lot to take in, but it’s simple to understand. The word piezoelectric originates from the Greek word piezein, which literally means to squeeze or press. Instead of squeezing grapes to make wine, we’re squeezing crystals to make an electric current! Piezoelectricity is found in a ton of everyday electronic devices, from quartz watches to speakers and microphones. In a nutshell:
Piezoelectricity is the process of using crystals to convert mechanical energy into electrical energy, or vice versa.
Regular crystals are defined by their organized and repeating structure of atoms that are held together by bonds, this is called a unit cell. Most crystals, such as iron have a symmetrical unit cell, which makes them useless for piezoelectric purposes.
There are other crystals that get lumped together as piezoelectric materials. The structure in these crystals aren’t symmetrical but they still exist in an electrically neutral balance. However, if you apply mechanical pressure to a piezoelectric crystal, the structure deforms, atoms get pushed around, and suddenly you have a crystal that can conduct an electrical current. If you take the same piezoelectric crystal and apply an electric current to it, the crystal will expand and contract, converting electrical energy into mechanical energy.
There are a variety of piezoelectric materials that can conduct an electric current, both man-made and natural. The most well known, and the first piezoelectric material used in electronic devices is the quartz crystal. Other naturally occurring piezoelectric materials include cane sugar, Rochelle salt, topaz, tourmaline, and even bone.
As piezoelectric technology started to take off after World War I we began developing man-made materials to rival the performance of quartz. Man-made piezoelectric materials include:
PZT is made from lead zirconate titanate and can produce more voltage than quartz with the same amount of mechanical pressure.
PZT piezo ceramics used in ultrasonic sensors
Barium Titanate is a ceramic piezoelectric material that was discovered during World War II and is known for its long lasting durability.
Lithium Niobate is a material that combines oxygen, lithium, and nobium together in a ceramic material that performs similar to barium titanate.