Y = Yttrium.
TZP = Tetragonal Zirconia Polycrystal.
Y-TZP is a partly stabilized zirconium or Yttria-stabilized zirconium.
Pure zirconium dioxide changes from monoclinic (stable at room temperature) to tetragonal (at about 1173 °C) and then to cubic phase (at about 2370 °C).
These are 2 examples. For more, have a look in the Glossary!