A dielectric film, contains: (1) Bi and Ti; (2) at least one element E1 selected from the group consisting of Na and K; and (3) at least one element E2 selected from the group consisting of Ba, Sr, and Ca. The dielectric film has a main phase containing an oxide that contains Bi, Ti, the element E1, and the element E2 and has a perovskite structure, and a subphase that contains Bi and has an oxygen concentration lower than that of the main phase. In a sectional surface of the dielectric film, a ratio RS of an area of the subphase to a sum of an area of the main phase and the area of the subphase is greater than or equal to 0.03 and less than or equal to 0.3.

A piezoelectric ceramic, which does not contain lead as a constituent element, is characterized in that: its primary component is a perovskite compound expressed by the composition formula (Bi.sub.0.5x/2Na.sub.0.5x/2Ba.sub.x)(Ti.sub.1yMn.sub.y)O.sub.3 (where 0.01x0.25, 0.001y0.020); and the coefficient of variation (CV) in grain size among the grains contained therein is 35 percent or lower. The piezoelectric ceramic presents an improved dielectric loss tangent tan .

A piezoelectric material including a perovskite-type metal oxide represented by the following general formula (1); Bi; and Mn, wherein the content of Bi is 0.1-0.5 mol % with respect to 1 mol of the metal oxide, the content of Mn is 0.3-1.5 mol % with respect to 1 mol of the metal oxide, and the piezoelectric material satisfies (L.sub.4L.sub.5)/L.sub.50.05 and (L.sub.8L.sub.9)/L.sub.90.05 when the lengths of twelve BiO bonds with Bi that is located at a 12-fold site with respect to O in a perovskite-type unit cell as a starting point are taken to be L.sub.1 to L.sub.12 in length order:
(Ba.sub.1-xM1.sub.x)(Ti.sub.1-yM2.sub.y)O.sub.3(1)
wherein 0x0.2, 0y0.1, and M1 and M2 are mutually different metal elements which have a total valence of +6 and are selected from other elements than Ba, Ti, Bi and Mn.

A piezoelectric material including a perovskite-type metal oxide represented by the following general formula (1); Bi; and Mn, wherein the content of Bi is 0.1-0.5 mol % with respect to 1 mol of the metal oxide, the content of Mn is 0.3-1.5 mol % with respect to 1 mol of the metal oxide, and the piezoelectric material satisfies (L.sub.4L.sub.5)/L.sub.50.05 and (L.sub.8L.sub.9)/L.sub.90.05 when the lengths of twelve BiO bonds with Bi that is located at a 12-fold site with respect to O in a perovskite-type unit cell as a starting point are taken to be L.sub.1 to L.sub.12 in length order:
(Ba.sub.1-xM1.sub.x)(Ti.sub.1-yM2.sub.y)O.sub.3(1)
wherein 0x0.2, 0y0.1, and M1 and M2 are mutually different metal elements which have a total valence of +6 and are selected from other elements than Ba, Ti, Bi and Mn.

A piezoelectric thin film 3 contains a metal oxide, the metal oxide contains bismuth, potassium, titanium, iron and element M, the element M is at least one of magnesium and nickel, at least a part of the metal oxide is a crystal having a perovskite structure, and a (001) plane, a (110) plane or a (111) plane of the crystal is oriented in a normal direction dn of the surface of the piezoelectric thin film 3.

A piezoelectric thin film 3 contains a metal oxide, the metal oxide contains bismuth, potassium, titanium, iron and element M, the element M is at least one of magnesium and nickel, at least a part of the metal oxide is a crystal having a perovskite structure, and a (001) plane, a (110) plane or a (111) plane of the crystal is oriented in a normal direction dn of the surface of the piezoelectric thin film 3.

There is disclosed a piezoelectric ceramic having the composition: a[PbTiO.sub.3]-b[SrTiO.sub.3]-c[BiFeO.sub.3]-d[(K.sub.xBi.sub.1-x)TiO.sub.3]; wherein 0.4<x<0.6; 0.1<a<0.4; 0.01<b0.2; c0.05; d0.01; and a+b+c+d=1 optionally comprising an A- or B-site metal dopant in an amount of up to 2 at. %.

There is disclosed a piezoelectric ceramic having the composition: a[PbTiO.sub.3]-b[SrTiO.sub.3]-c[BiFeO.sub.3]-d[(K.sub.xBi.sub.1-x)TiO.sub.3]; wherein 0.4<x<0.6; 0.1<a<0.4; 0.01<b0.2; c0.05; d0.01; and a+b+c+d=1 optionally comprising an A- or B-site metal dopant in an amount of up to 2 at. %.

The present invention relates to a method for identifying a solid solution ceramic material of a plurality of perovskite compounds which exhibits an electric field induced strain derived from a reversible phase transition, as well as a method for making such ceramic materials and ceramic materials obtainable therefrom. In particular, the present invention is directed to a method of identifying a solid solution ceramic material of at least three perovskite compounds which exhibits an electric field induced strain derived from a reversible phase transition; said method comprising the steps of: i) determining a molar ratio of at least one tetragonal perovskite compound to at least one non-tetragonal perovskite compound which, when combined to form a solid solution, provides a ceramic material comprising a major portion of a tetragonal phase having an axial ratio c/a of greater than 1.005 to 1.04; and ii) determining a molar ratio of at least one additional non-tetragonal perovskite compound to the combination of perovskite compounds from step i) at the determined molar ratio which, when combined to form a solid solution, provides a ceramic material comprising a major portion of a pseudo-cubic phase having an axial ratio c/a of from 0.995 to 1.005 and/or a rhombohedral angle of 900.5 degrees.

The present invention relates to a method for identifying a solid solution ceramic material of a plurality of perovskite compounds which exhibits an electric field induced strain derived from a reversible phase transition, as well as a method for making such ceramic materials and ceramic materials obtainable therefrom. In particular, the present invention is directed to a method of identifying a solid solution ceramic material of at least three perovskite compounds which exhibits an electric field induced strain derived from a reversible phase transition; said method comprising the steps of: i) determining a molar ratio of at least one tetragonal perovskite compound to at least one non-tetragonal perovskite compound which, when combined to form a solid solution, provides a ceramic material comprising a major portion of a tetragonal phase having an axial ratio c/a of greater than 1.005 to 1.04; and ii) determining a molar ratio of at least one additional non-tetragonal perovskite compound to the combination of perovskite compounds from step i) at the determined molar ratio which, when combined to form a solid solution, provides a ceramic material comprising a major portion of a pseudo-cubic phase having an axial ratio c/a of from 0.995 to 1.005 and/or a rhombohedral angle of 900.5 degrees.