Ferroelectric ceramics, electronic component and manufacturing method of ferroelectric ceramics
Ferroelectric ceramics including: a Pb(Zr 1-B Ti B )O 3 seed crystal film formed on a foundation film; and a Pb(Zr 1-x Ti x )O 3 crystal film, wherein: the seed crystal film is formed by sputtering while the foundation film is being disposed on an upper side of a sputtering target and the foundation film is being made to face the sputtering target; in the seed crystal film, a Zr/Ti ratio on the crystal film side from the center in the thickness direction thereof is larger than a Zr/Ti ratio on the foundation film side from the center in the thickness direction thereof; the crystal film is crystallized by coating and heating a solution containing, in an organic solvent, a metal compound wholly or partially containing ingredient metals of the crystal film and a partial polycondensation product thereof; and the B and the x satisfy formulae 2 and 3, respectively, below, 0.1< B <1 formula 2 0.1< x <1 formula 3.
1. Ferroelectric ceramics comprising:
a foundation film;
a Pb(Zr 1-A Ti A )O 3 film formed on the foundation film;
a Pb(Zr 1-B Ti B )O 3 seed crystal film formed, by sputtering, on the Pb(Zr 1-A Ti A )O 3 film; and
a Pb(Zr 1-x Ti x )O 3 crystal film formed on the Pb(Zr 1-B Ti B )O 3 seed crystal film, wherein:
the foundation film is a Pt film oriented to (100), or the foundation film is a double-layer film comprising a Pt film oriented to (100) and a SrRuO 3 film formed on the Pt film and oriented to (001);
the Pb(Zr 1-A Ti A )O 3 film is in contact with the foundation film;
the Pb(Zr 1-x Ti x )O 3 crystal film is crystallized by coating and heating a solution containing, in an organic solvent, a metal compound wholly or partially containing ingredient metals of the Pb(Zr 1-x Ti x )O 3 crystal film and a partial polycondensation product thereof;
a Zr/Ti ratio in the Pb(Zr 1-x Ti x )O 3 crystal film in the thickness direction thereof becomes gradually smaller or decreases in steps with increase in distance from the Pb(Zr 1-B Ti B )O 3 seed crystal film;
a Zr/Ti ratio in the Pb(Zr 1-B Ti B )O 3 seed crystal film in the thickness direction thereof becomes gradually larger with increase in distance from the Pb(Zr 1-A Ti A )O 3 film toward the Pb(Zr 1-x Ti x )O 3 crystal film;
the Pb(Zr 1-x Ti x )O 3 crystal film comprises a Pb(Zr 0.70 Ti 0.30 )O 3 film formed on the Pb(Zr 1-B Ti B )O 3 seed crystal film, a Pb(Zr 0.65 Ti 0.35 )O 3 film formed on the Pb(Zr 0.70 Ti 0.30 )O 3 film, and a plurality of PZT films stacked and formed on the Pb(Zr 0.65 Ti 0.35 )O 3 film;
a Zr/Ti ratio in each of the Pb(Zr 0.70 Ti 0.30 )O 3 film, the Pb(Zr 0.65 Ti 0.35 )O 3 film, and the plurality of PZT films in the thickness direction thereof becomes gradually smaller with increase in distance from the Pb(Zr 1-B Ti B )O 3 seed crystal film;
a polarization direction of the Pb(Zr 1-B Ti B )O 3 seed crystal film is identical to a polarization direction of the Pb(Zr 1-x Ti x )O 3 crystal film;
the Pb(Zr 1-B Ti B )O 3 seed crystal film and the Pb(Zr 1-x Ti x )O 3 crystal film are oriented to (001); and
the A, the B and the x satisfy formulae 1 to 3, respectively,
0≤ A≤ 0.1 formula 1
0.1< B< 1 formula 2
0.1< x< 1 formula 3.
2. The ferroelectric ceramics according to claim 1 , wherein:
the Pb(Zr 1-B Ti B )O 3 seed crystal film is formed by sputtering while the Pb(Zr 1-A Ti A )O 3 film is being disposed on an upper side of a sputtering target and the Pb(Zr 1-A Ti A )O 3 film is being made to face the sputtering target.
3. The ferroelectric ceramics according to claim 1 , wherein a ratio of Pb to (Zr+Ti) in each of the Pb(Zr 1-B Ti B )O 3 seed crystal film and the Pb(Zr 1-x Ti x )O 3 crystal film satisfies formula 5 below,
Pb/(Zr+Ti)<1.06 formula 5.
4. The ferroelectric ceramics according to claim 1 , wherein:
the B is 0.42;
the x is 0.4; and
the thickness of the Pb(Zr 1-x Ti x )O 3 crystal film, in which the Zr/Ti ratio becomes gradually smaller or decreases in steps with increase in distance from the Pb(Zr 1-B Ti B )O 3 seed crystal film, is 12 times larger than the thickness of the Pb(Zr 1-B Ti B )O 3 seed crystal film, in which the Zr/Ti ratio becomes gradually larger with increase in distance from the Pb(Zr 1-A Ti A )O 3 film toward the Pb(Zr 1-x Ti x )O 3 crystal film.
5. An electronic component comprising the ferroelectric ceramics according to claim 1 .
6. A method of manufacturing the ferroelectric ceramics according to claim 1 , comprising the steps of:
forming a Pb(Zr 1-B Ti B )O 3 seed crystal film, by sputtering, on a Pb(Zr 1-A Ti A )O 3 film;
coating a solution containing a metal compound wholly or partially containing, in an organic solvent, ingredient metals of the Pb(Zr 1-B Ti B )O 3 seed crystal film and a partial polycondensation product thereof onto the Pb(Zr 1-B Ti B )O 3 seed crystal film to thereby form a noncrystalline precursor film; and
heating the Pb(Zr 1-B Ti B )O 3 seed crystal film and the noncrystalline precursor film in an oxygen atmosphere to thereby oxidize and crystallize the noncrystalline precursor film and to thereby form a Pb(Zr 1-x Ti x )O 3 crystal film, wherein:
formation of the Pb(Zr 1-B Ti B )O 3 seed crystal film is performed by sputtering while the Pb(Zr 1-A Ti A )O 3 film is being disposed on an upper side of a sputtering target and the Pb(Zr 1-A Ti A )O 3 film is being made to face the sputtering target; and
the A, the B and the x satisfy formulae 1 to 3, respectively, below,
0≤ A≤ 0.1 formula 1
0.1< B< 1 formula 2
0.1< x< 1 formula 3.
7. The manufacturing method of ferroelectric ceramics according to claim 6 , wherein a polarization direction of the Pb(Zr 1-B Ti B )O 3 seed crystal film immediately after forming the Pb(Zr 1-B Ti B )O 3 seed crystal film by sputtering is identical to a polarization direction of a Pb(Zr 1-x Ti x )O 3 crystal film immediately after forming the Pb(Zr 1-x Ti x )O 3 crystal film by oxidizing and crystallizing the noncrystalline precursor film.
8. The manufacturing method of ferroelectric ceramics according to claim 6 , wherein:
the noncrystalline precursor film is formed by coating a plurality of times the solutions on the Pb(Zr 1-B Ti B )O 3 seed crystal film; and
in the solutions that are coated the plurality of times, a Zr/Ti ratio in a solution that is coated onto the Pb(Zr 1-B Ti B )O 3 seed crystal film from the center of the noncrystalline precursor film in the thickness direction is larger than a Zr/Ti ratio in a solution that is coated onto the side opposite to the Pb(Zr 1-B Ti B )O 3 seed crystal film from the center of the noncrystalline precursor film in the thickness direction.
9. The manufacturing method of ferroelectric ceramics according to claim 8 , wherein, in the solutions that are coated the plurality of times, a Zr/Ti ratio in each of the solutions for the noncrystalline precursor film in the thickness direction thereof becomes gradually smaller with increase in distance from the Pb(Zr 1-B Ti B )O 3 seed crystal film.
10. The manufacturing method of ferroelectric ceramics according to claim 6 , wherein, in the Pb(Zr 1-B Ti B )O 3 seed crystal film, a Zr/Ti ratio on the Pb(Zr 1-x Ti x )O 3 crystal film side from the center in the thickness direction thereof is larger than a Zr/Ti ratio on the Pb(Zr 1-A Ti A )O 3 film side from the center in the thickness direction thereof.
11. The manufacturing method of ferroelectric ceramics according to claim 6 , wherein a ratio of Pb to (Zr+Ti) in each of the Pb(Zr 1-B Ti B )O 3 seed crystal film and the Pb(Zr 1-x Ti x )O 3 crystal film satisfies a formula 5 below,
Pb/(Zr+Ti)<1.06 formula 5.