PURPOSE: To reduce dispersion of sensitivity of piezoelectric property to temperature in a bismuth layer compound.

CONSTITUTION: This bismuth layer compound is characterized by being expressed by the chemical structural formula {(M11-yPby)1-2X-M2XBi4+X}Ti4O15 [wherein M1 is alkaline earth metal; M2 is alkali metal; 0.06≤(x)≤0.44 and 0<(y)≤1.0]. Since Pb alone or an alkaline earth metal containing Pb and an alkali metal are contained in a prescribed ratio, dispersion of sensitivity of piezoelectric property to temperature becomes small, though the reason is unknown and the compound can be used in a broad temperature range. Since Pb is contained as an essential component, dependence of sensitivity of piezoelectric property to temperature can be controlled, tough the reason is also unknown.