Piezoelectric Materials - a brief description
The most common piezoelectric materials technically used are the single crystal materials quartz, tourmaline, gallium phosphate, lithium niobate, lithium tantalate and piezoceramics.
Depending on the specific application, the set of material properties of interest differs to a large extent. Therefore, a general comparison can only be a high level listing of properties.

Point group (32)
Main members: quartz, gallium phosphate, and langasite
Even though quartz is, after feldspar, the most common mineral found on earth, a few million tons are still synthetically produced annually. Quartz has a comparably high mechanical strength of 2-3 GPa, is almost insoluble in water and is highly resistant against most acids and alkali. Its melting point is 1710°C.

Gallium phosphate is the most promising quartz-homeotypic crystal. It shares many positive features of quartz e.g. the high mechanical strength, but outperforms it with respect to many interesting properties, in particular the higher electro-mechanical coupling and its greater piezoelectric sensitivity at temperatures up to 970°C.

Since the early 1980's when research in new piezoelectric compounds was intensified, the CGG (Ca3Ga2Ge4O14) had been developed to comprise an entire group of crystal materials with at least 40 members. The different crystals are obtained by variations of the cations of CGG. The main materials are LGS (langasite), LGG (lanthan gallium germanate), LGT (lanthan gallium tantalate), LGN (lanthan gallium niobate) and SGG (strontium gallium germanate). A general property of this group is the high temperature stability, which is much higher compared to quartz. Langasite is used for high volume BAW and SAW applications due to its high coupling and its availability in large dimensions (4 inch wafers).

Symmetry class 3m
Main members: tourmaline, LiNbO3, LiTaO3
From a chemical point of view, tourmaline is a complex aluminium-borosilicate (Na, Ca) (Mg, Fe)3 B3 Al6 Si6 (O,OH,F)31, sometimes containing Li, Mn, Ti, Fe or Cr. These elements contribute, in a large extent, to the changing colors of tourmalines, by allowing for ion charge transfers. Tourmaline has a high mechanical stability and has similar resistance, as quartz does, to many acids and alkaline solutions. Very pure tourmalines can be used beyond 900°C, the actual technical limit is 750 - 780 °C. Additionally tourmaline shows significant pyroelectricity.

Ceramics
Piezoelectric ceramics have gained increasing importance over the last years. The reason is their much higher piezoelectric constant (two orders of magnitude) than single crystal materials and are obtained in comparably simple sintering processes. Piezoceramics consist of a large number of piezoelectric crystallites, with domains where the electric dipoles are aligned. The single domains are initially randomly oriented and have to be polarized to obtain a functional piezo material. Typical materials are PZT (lead-zirkonite-titanate mixed ceramics), bismuth titanate or lead metaniobate.