A piezoelectric material for a combustion pressure sensor, a method for producing the piezoelectric material, and a combustion pressure sensor using the piezoelectric material are provided. The piezoelectric material of the present invention includes a single crystal containing Ca, Ta, an element M (M is Al or Ga), Si, and O, the single crystal has the same crystal structure as the crystal structure of langasite represented by La.sub.3Ga.sub.5SiO.sub.14, and at least the content of the element M is insufficient for the stoichiometric composition represented by Ca.sub.3TaM.sub.3Si.sub.2O.sub.14. Preferably, in a case where the element M is Ga, each content of the Ca and the Si is excessive for the stoichiometric composition, and in a case where the element M is Al, the content of the Ca is excessive for the stoichiometric composition, and the content of the Ta is insufficient for the stoichiometric composition.

According to embodiment, a piezoelectric transducer includes a polarized single crystal piezoelectric body comprising a lead complex perovskite compound containing niobium oxide and at least one of magnesium oxide and indium oxide and including a first plane whose crystal orientation is [100] and a second plane which faces the first plane and whose crystal orientation is [100], and first electrode provided on the first plane side of the body and a second electrode provided on the second plane side of the body. A ratio of a second FWHM of diffracted X-rays at the Miller index (400) of the body to a first FWHM of diffracted X-rays at the miller index (400) of the body which is unpolarized or has undergone depolarization processing is not less than 0.22 and not more than 0.4.

A method for producing a piezoelectric film includes forming a metal film, recrystallizing a portion of the metal film by heating, forming an amorphous film of piezoelectric material on the metal film; and heating the amorphous film at a position of the recrystallized portion of the metal film.