The present invention provides a piezoelectric substance of single crystal or uniaxial crystal type in which three lattice lengths a, b and c of a unit lattice of the piezoelectric substance are smaller than lattice length a.sub.0, b.sub.0 and c.sub.0 of a unit lattice of a bulk state of single crystal having the same temperature and same composition, respectively, and a volume of the unit lattice of the piezoelectric substance is smaller than a volume of the unit lattice of the bulk state of single crystal having the same temperature and same composition.