The piezoelectric effect was discovered by 2 French physicists,
Pierre Curie (Younger brother 1859-1906)
and Jacques Curie (Older brother 1856-1941).
It is said that they discovered this phenomenon when they were conducting an experiment on crystallization of crystals.
Many think that they also
discovered the pyroelectric effect but this phenomenon had been discovered
a long time before them.
The pyroelectric effect was reported by Epinus in his paper on Electronic stones at Memoirs of the Berlin Academyn.
It went through Becquerel/Thomson's experiment and then it was finally formulated by Riecke in 1885.
The pyroelectric was not discovered by Curie brothers.
It is said that the brothers discovered the piezoelectric effect
when they were conducting an experiment on the already known pyroelectric effect.