The piezoelectric effect is generally stronger in materials that also show pyroelectricity. (Pyroelectricity is the ability of a material to generate electricity if its temperature changes.) All pyroelectric materials are also piezoelectric. We can use these materials to convert between thermal, mechanical, and electrical energy. For instance, we can put a pyroelectrical crystal in a furnace. If we take out and let it cool without applying any force to it, it will generate a large static charge. This type of crystal is most common in motion sensors. That is because the tiny rise in temperature from a warm body entering a room is enough to produce a voltage in the crystal. A motion sensor reads that voltage and converts it to data. 