A dielectric composition that contains a first complex oxide represented by (Bi.sub.xNa.sub.1−x)TiO.sub.3—CaTiO.sub.3 and having a perovskite structure as a main component; and at least one second complex oxide having a perovskite structure selected from the group consisting of BaZrO.sub.3, SrZrO.sub.3, CaZrO.sub.3, NaNbO.sub.3, and NaTaO.sub.3 as an auxiliary component. A tolerance factor t when the at least one second complex oxide is BaZrO.sub.3, NaNbO.sub.3, or NaTaO.sub.3 is 0.9016≤t≤0.9035, a tolerance factor t when the at least one second complex oxide is SrZrO.sub.3 is 0.9005≤t≤0.9025, and a tolerance factor t when the at least one second complex oxide is CaZrO.sub.3 is 0.9000 t<0.9020.

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.0.5−x/2Na.sub.0.5−x/2Ba.sub.x)(Ti.sub.1−yMn.sub.y)O.sub.3 (where 0.01≤x≤0.25, 0.001≤y≤0.020); 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 δ.

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.0.5−x/2Na.sub.0.5−x/2Ba.sub.x)(Ti.sub.1−yMn.sub.y)O.sub.3 (where 0.01≤x≤0.25, 0.001≤y≤0.020); 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 δ.

A composite fiber composed of at least a metal sintered body and a ceramic sintered body. In the composite fiber, the metal sintered body and the ceramic sintered body are adjacent to each other. The composite fiber having the metal sintered body and the ceramic sintered body can have a tensile strength of 5 kgf/mm.sup.2 or more.

A composite fiber composed of at least a metal sintered body and a ceramic sintered body. In the composite fiber, the metal sintered body and the ceramic sintered body are adjacent to each other. The composite fiber having the metal sintered body and the ceramic sintered body can have a tensile strength of 5 kgf/mm.sup.2 or more.

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.

The invention relates to a lead-free piezoceramic material based on bismuth sodium titanate (BST) having the following parent composition: x(Bi.sub.0.5Na.sub.0.5)TiO.sub.3-yBaTiO.sub.3-zSrTiO.sub.3 where x+y+z=1 and 0<x<1, 0<y<1, 0≤z≤0.07 or x(Bi.sub.0.5Na.sub.0.5)TiO.sub.3-yBaTiO.sub.3-zCaTiO.sub.3 where x+y+z=1 and 0<x<1, 0<y<1, 0<z≤0.05 or x(Bi.sub.0.5Na.sub.0.5)TiO.sub.3-y(Bi.sub.0.5K.sub.0.5)TiO.sub.3-zBaTiO.sub.3 where x+y+z=1 and 0<x<1, 0<y<1, 0≤z<1, characterized by addition of a phosphorus-containing material in a quantity that gives a phosphorus concentration of from 100 to 2000 ppm in the piezoceramic material.

The invention relates to a lead-free piezoceramic material based on bismuth sodium titanate (BST) having the following parent composition: x(Bi.sub.0.5Na.sub.0.5)TiO.sub.3-yBaTiO.sub.3-zSrTiO.sub.3 where x+y+z=1 and 0<x<1, 0<y<1, 0≤z≤0.07 or x(Bi.sub.0.5Na.sub.0.5)TiO.sub.3-yBaTiO.sub.3-zCaTiO.sub.3 where x+y+z=1 and 0<x<1, 0<y<1, 0<z≤0.05 or x(Bi.sub.0.5Na.sub.0.5)TiO.sub.3-y(Bi.sub.0.5K.sub.0.5)TiO.sub.3-zBaTiO.sub.3 where x+y+z=1 and 0<x<1, 0<y<1, 0≤z<1, characterized by addition of a phosphorus-containing material in a quantity that gives a phosphorus concentration of from 100 to 2000 ppm in the piezoceramic material.

Provided is a piezoelectric ceramics including crystal grains each including: a first region that is formed of a perovskite-type metal oxide having a crystal structure in which a central element of a unit cell is located at an asymmetrical position; and a second region that is formed of a perovskite-type metal oxide having a crystal structure in which a central element of a unit cell is located at a symmetrical position, and that is present inside the first region, wherein a ratio of a cross-sectional area of the second region to a cross-sectional area of the piezoelectric ceramics is 0.1% or less.