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All electronics technology is built upon a foundation of materials technology which itself is built upon the physics of condensed materials and quantum mechanics. The educational foundation for understanding electronic devices is the assumption of linearity in all devices except for those, like transistors, where non-linear equations simplified from condensed matter physics are utilized. The typical electrical engineer's only exposure to non-linear capacitors is with power by-pass capacitors that have very wide capacitance tolerances and/or high temperature coefficients. He or she may think the wide variations in the specified capacitance values of these capacitors arise because they are cheaply made. In reality, most non-precision capacitors are fabricated with PZT or a related material to achieve extremely high capacitance density in small volumes. Without PZT, 1µF surface mount capacitors would not exist! Trillions of surface mount capacitors are fabricated every year to service mankind's ever growing thirst for electronics. The acronym PZT stands for Lead Zirconate Titanate, a solid solution or cystal of the given metal oxides that has strong non-linear electrical properties. The capacitance value of a device fabricated with PZT or Barium Titanate or Strontium Titanate or Lead Manganate Niobate or any of the thousands of other non-linear dielectric materials is different at each voltage that may be forced across it. That forces the manufacturers to specify wide capacitance value tolerances. These capacitors do not have remanent hysteresis because that property has been killed by the addition of dopants. Their pyroelectric property, also suppressed in manufacturing by the addition of dopants, still causes them to change their capacitance significantly over electronic operating temperatures. People who do this type of research are materials scientists and they utilize the test equipment Radiant manufactures to characterized their materials.
The discrete ferroelectric capacitors offered by Radiant are also PZT but they are not doped. They maintain their pristine ferroelectric, piezoelectric, and pyroelectric properties. For the first, time, such capacitors made with ferroelectric films less than one micron thick are avaiable for use in electronic circuits. If you are not familiar with non-linear materials and their electrical properties, the following five lessons on capacitance will be useful to help you understand ferroelectric capacitors.
In addition, there are two slide presentations referenced in the lessons above that explain capacitance and the origin of piezoelectricity and pyroelectricity in simple terms.
These seven documents are from the lesson plan provided with the Radiant EDU. The Radiant EDU documentation includes these tutorials and more plus a series of experiments that may be executed on Type AB or Type AL capacitors with the EDU. Go to this link to learn more. | 
