WO2000026924A1

WO2000026924A1 - PREPARATION METHOD FOR LOW-TEMPERATURE-SINTERABLE Pb-BASED PEROVSKITE DIELECTRIC POWDERS

Info

Publication number: WO2000026924A1
Application number: PCT/KR1998/000347
Authority: WO
Inventors: Kyoung Ran Han; Sojin Kim; Hee Jin Koo
Original assignee: Korea Institute Of Science And Technology
Priority date: 1998-10-31
Filing date: 1998-10-31
Publication date: 2000-05-11

Abstract

There is disclosed a preparation method for a perovskite PMN dielectric powder, including: mixing PbO powder with Nb2O5 powder; adding a solution in which Mg2+ is dissolved to a slurry of the mixture; obtaining a PMN (Pb(Mg¿1/3?Nb2/3)O3) precursor by removing the solvent from the above solution; and calcining the precursor powder at 800°-950 °C and sintering the calcined powder. Also disclosed is a preparation method for a perovskite PMN-PT dielectric powder, including: mixing PbO with Nb2O5 powder; adding a solution in which Mg?2+¿ is dissolved to a slurry of the mixture; obtaining a PMN (Pb(Mg¿1/3?Nb2/3)O3) precursor by removing the solvent from the solution; obtaining a PMN-PT (0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3) precursor by mixing the above PMN precursor with PbTiO3 powder and drying the mixture; and calcining the PMN-PT precursor powder at 750°-950 °C and sintering the calcined powder. Further disclosed is a preparation method for a perovskite PMN-PT dielectric powder, including: mixing PbO, Nb2¿O¿5 and TiO2 powder; adding a solution in which Mg2+ is dissolved to a slurry of the mixture; obtaining a PMN-PT precursor powder by removing the solvent from the solution; and calcining the precursor powder at 800°-950 °C and sintering the calcined powder.

Description

PREPARATION METHOD FOR LOW-TEMPERATURE-SINTERABLE Pb-BASED PEROVSKITE DIELECTRIC POWDERS

TECHNICAL FIELD The present invention relates to low-temperature-sinterable Pb-based perovskite dielectric powders, and more particularly to preparation methods for (1-x)[Pb(Mg_1/3Nb_2/3)O₃] - x(PbTiO₃)[(1-x) PMN-xPT) (wherein, x = 0 - 0.1 ).

BACKGROUND ART Preparation methods for PMN or PMN-PT used for multi-layered ceramic capacitors (MLCC) or relaxors, which have been generally applied so far, are a mixed-oxide method of PbO, MgO and Nb₂O₅ and a sol-gel method which uses organometalic compounds.

Since the conventional mixed-oxide method is always accompanied by the unwanted cubic pyrochlore phase because the reaction of PbO with Nb₂O₅ occurs prior to the reaction of MgO, a modified method which is commercially in use includes the steps of preparation of a precursor with the columbite structure by reacting MgO with Nb₂O₅ and reacting the precursor with PbO. More specifically, in order to inhibit the reaction between PbO and Nb₂O₅ which provides the undesirable pyrochlore phase in the method which undergoes via the columbite precursor, first, MgNb₂O₆ which is the columbite precursor is obtained by reacting MgO with Nb₂O₅ at a temperature of 1100°-1200°C, and then PMN with >95% of the perovskite phase is prepared by reacting MgNb₂O₆ with PbO at a temperature of 800°-900°C. The perovskite single phase PMN-PT powder can be prepared by mixing the above PMN powder with PbTiO₃ which has been obtained by mixing PbO and TiO₂ in the molar ratio of 1 :1 and heat- treating the mixture at a temperature of 800°C.

Since the perovskite phase PMN and PMN-PT powders are usually required to be sintered at temperatures of 1100°-1200°C to have >95% relative density, many studies have been focused on reducing the sintering temperature below 1100°C to be used for MLCC, so that low-cost Pd-Ag can be applied for the metal internal electrodes.

U.S. Patent No. 5,004,715 discloses that when adding CuO to PMN or PMN-PT powder, the sintering temperature can be reduced to 950°-975°C, so that low-cost Cu internal electrodes can be used, besides the bending strength thereof can be improved >1000 Kg/cm². It is shown that the compound according to the reference, which has a dielectric constant of 11000-13000 at 20°C, a specific resistivity of ~10¹² Ω-cm, a 1.5-3% loss of dielectric constant and >97% of relative density, can be prepared by which appropriate amounts of PbO, MgO, Nb₂O₅, TiO₂ and 3-10 mol% of CuO are placed in a polypropylene bottle, mixed with CaO-stabilized ZrO balls, calcined at 800°C for 2 hours and then sintered at 950°-975°C. Further, U.S. Patent No. 5,680,291 discloses that a preparation method for low-temperature-sinterable PMN-PT is provided by adding PbO, CuO and CaO to PMN or PMN-PT using the columbite method. According to the reference, first, PMN is prepared from a mixture of the MgNb₂O₆ columbite precursor, obtained by ball-milling MgO and Nb₂O₅ and heat-treating the mixture at 1100°-1200°C, and reacting the columbite precursor with PbO at 900°C, and then with PbTiO₃, prepared by mixing PbO and TiO₂ in the molar ratio of 1 :1 and calcining at a temperature of 800°C, and PbO, CaO and CuO are added thereto, and calcination at a temperature of 750°-850°C follows whereby, thus the low-temperature-sinterable PMN-PT powder is prepared. The above PMN- PT powder that is sintered at 845°-950° has a dielectric constant of 13000-

16000 at 20°C, a specific resistivity of ~10¹¹ Ω cm and a 1.2-1.8% loss of dielectric constant. However, the reference does not disclose the sintered density and bending strength.

The above-mentioned references suggest the possibility of using Cu electrodes for the fabrication of a MLCC. However, the first reference with the simple one-step calcination process which is applied to the mixed-oxide method requires relatively high sintering temperatures of 950°-975°C, and the second reference has the cost problem due to the four calcination-milling processes for the powder preparation, though having low sintering temperatures of 845°- 950°C.

DISCLOSURE OF THE INVENTION

Accordingly, an object of the present invention is to provide a method for preparing PMN and PMN-PT powders with a pure perovskite phase via one- step calcination process to prevent a pyrochlore phase being formed due to the reaction between Nb₂O₅ with PbO prior to the reaction of MgO.

To achieve the above object, an embodiment according to the present invention provides a preparation method for perovskite PMN dielectric powder, which includes ball-milling PbO and Nb₂O₅ in alcohol to form a slurry, adding an aqueous solution in which Mg²⁺ is dissolved to the above slurry, obtaining a PMN(Pb(Mg_1/3Nb_2/3)O₃) precursor by removing the solvent from the slurry, and performing calcination of the PMN precursor powder at a temperature of 800°- 950°C and sintering the resultant powder.

Another embodiment according to the present invention provides a preparation method for perovskite PMN-PT dielectric powder, which includes compounding PbO and Nb₂O₅, adding an aqueous solution in which Mg²⁺ is dissolved to an alcoholic slurry of PbO and Nb₂O₅, obtaining a PMN (Pb(Mg_1/3Nb_2/3)O₃) precursor by removing the solvent from the solution, obtaining a PMN-PT (0.9Pb(Mg_1/3Nb_2/3)O₃-0.1 PbTiO₃)precursor by mixing and drying the PMN precursor and PbTiO₃, and performing calcination of the PMN- PT precursor powder at a temperature of 750°-950°C and sintering the resultant powder. Wherein, it is desirable that the PbTiO₃ is in the form of a single-phase tetragonal powder prepared by precipitating an aqueous TiCI₄ solution with ammonia over a slurry of PbO, wherein the precipitate is filtered, washed and dried, which is followed by calcination at 500°-600°C.

In addition, another embodiment according to the present invention provides a preparation method for a perovskite PMN-PT dielectric powder, which includes ball-milling of PbO, Nb₂O₅ and TiO₂ powder in alcohol to form a slurry, adding an aqueous solution in which Mg²⁺ is dissolved to the alcoholic slurry, obtaining a PMN-PT precursor by removing the solvent from the slurry, and performing calcination of the PMN-PT precursor powder at temperatures of 800°-950°C and sintering the resultant powder.

Additionally, in the above method, a solution in which Cu²⁺(2-5 mol%) is dissolved can be added before or after calcining the PMN-PT precursor. MODES FOR CARRYING OUT THE PREFERRED EMBODIMENTS

According to the present invention, a PMN precursor was prepared by adding Mg(NO₃)₂ which is soluble in water or alcohol, instead of MgO which has been used for conventional mixed-oxide methods, to an alcoholic slurry of PbO and Nb₂O₅ and removing the solvent. The PMN precursor was calcined at

950°C for 2 hours to have the pure perovskite phase. The PMN powder that was sintered at 900°-1100°C had a dielectric constant of 13700-14400 at 20°C, a specific resistivity of ~10¹⁰ Ω-cm, 0.05-0.4% loss of dielectric constant and >95% relative density. The above PMN precursor is mixed with crystalline PT, which was prepared via precipitation of titanium hydroxide from an aqueous TiCI₄ solution over PbO powder, the precipitate being filtered, washed and dried, which was followed by calcination at 600°C, and the resultant mixture was calcined at temperatures of 750°-950°C to thereby prepare a PMN-PT powder with a pure perovskite phase. The PMN-PT powder that was sintered at 850°-1200°C had a dielectric constant of 13000-25000, a specific resistivity of ~10¹⁰ Ω-cm, a 1.5- 7% loss of dielectric constant and 92-98% of relative density.

Additionally, a PMN-PT precursor was prepared by compounding PbO, Nb₂O₅ and TiO₂ with ball milling, adding Mg(NO₃)₂ thereto and drying the resultant. The precursor was calcined once at 850°-950°C, whereby a PMN-PT powder with a single perovskite phase was prepared. The PMN-PT powder that was sintered at 850°-1000°C had a dielectric constant of 14400-19000, a specific resistivity of ~10¹¹ Ω-cm, a 1-4% loss of dielectric constant and 94-98% of relative density. Further, 2-3 mol% of Cu(NO₃)₂, which had been dissolved in water or alcohol solution, instead of CuO, was added to the PMN-PT powders before or after calcination, whereby the sintering temperature could be reduced to 825°C. Such sintered powders had a dielectric constant of -15000, a specific resistivity of ~10¹¹ Ω-cm, and >98% relative density. Here, it is to be noted that the heating rate of the calcination or sintering process was 5°C/min., and the calcination or sintering proceeded for 10min-2hrs only within a closed alumina crucible so as to restrain the volatilization of PbO, without applying embedding powder, and then the furnace was cooled down. In addition, the dielectric constant and dielectric loss were measured at 20°C, 1 kHz and O.δVrms, and the electrical resistivity was measured after 1 min. since 25V DC has been applied.

Example 1

PbO(0.30mol:99.9% purity, Aldrich Chemical Co., USA) and Nb₂O₅(0.10mol: 99.9% purity, Aldrich Chemical Co., USA) were placed with isopropanol in a polypropylene bottle and ball milled with zirconia balls of 5mm diameter for 24 hrs, and an aqueous solution of Mg(NO₃)₂6H₂O (0.105mol: 98% purity, Aldrich Chemical Co., USA)was added thereto and then the mixture was additionally ball milled for 2 hrs and dried. The preformed powder was heat- treated at 900°C for 2 hrs to thereby obtain the PMN powder having the 100% pure perovskite phase, studied by using X-ray diffractometry (XRD). The powder which had been calcined was added to 0.5 wt% of PVA 217 (Kurari Co., Japan) and ball milled with ZrO₂ balls in distilled water in a polypropylene bottle for 24 hrs and then dried. The dried powder was sieved through a 100 mesh sieve and pressed into pellets under a pressure of 800kg/cm² using a mold having a diameter of 10 mm. The pellets were sintered at a temperature of 850°-1200°C for 2 hrs. The results of the sintered pallets are shown in Table 1. Here, it is noted that the grain size of the powder sintered at 950°C was 2-4 μm.

Table 1

Effect of Sintering Temperature on Density and Dielectric Properties of PMN

Example 2

PbTiO₃ with a tetragonal phase was prepared by precipitating titanium hydroxide from an aqueous TiCI₄ solution with ammonia at pH 9.5 over PbO powder in distilled water, the precipitate being filtered, washed and dried, which was followed by calcination at 600°C for 1 hr. The PbTiO₃ powder(0.03mol) and the PMN precursor powder(0.27mol) which had been prepared in Example 1 were placed with isopropanol in a polypropylene bottle and ball milled with ZrO₂ balls for 24 hrs and dried. When the mol% of MgO was varied at 98, 100, 105 and 110%, the volume of the perovskite phase of the resultant PMN-PT powder which had been formed after 2hr-calcination at 950°C showed 95.6, 98.7, 100 and 100%, respectively. Thus, 105 mol% of MgO was selected. When heat- treating the PMN-PT precursor powder prepared with such composition at 730°C for 2 hrs, the perovskite phase of 17.2% was developed, but when the preformed powder was calcined at 750°C and 950°C, respectively, for 2 hrs, the powder had the pure perovskite phase. Both calcined powders were bail milled with 0.5 wt% of PVA 217 and ZrO₂ balls in distilled water in a polypropylene bottle for 24 hrs and dried. The dried powder was sieved through a 100 mesh sieve and pressed into pellets under a pressure of 800kg/cm² using a mold having a diameter of 10 mm. The pellets were sintered at temperatures of 850°- 1200°C for 2 hrs. The results of the sintered pallets are shown in Table 2.

Table 2

Effect of Calcination Temperature on Density and Dielectric Properties of

0.9PMN-0.1 PT Powder

Example 3

PbO(1.0mol:99.9% purity, Aldrich Chemical Co., USA), Nb₂O₅(0.3mol: 99.9% purity, Aldrich Chemical Co., USA) and TiO₂ (0.1mol: anatase 99.9% purity, Aldrich Chemical Co., USA) were placed with isopropanol in a polypropylene bottle and ball milled with zirconia balls having a diameter of 5mm for 24 hrs, and an aqueous solution of Mg(NO₃)₂6H₂O (0.315mol: 98% purity, Aldrich Chemical Co., USA) was added thereto and then the mixture was additionally ball milled for 2 hrs and dried. The resultant powder was preformed and heat-treated at 950°C for 2 hrs to thereby obtain the PMN-PT powder having the 100% pure perovskite phase, studied by using XRD. The powder which had been calcined was treated in accordance with the method performed in Example 2 and sintered at 850°-950°C for 2 hrs. The properties of the sintered pellets are shown in Table 3.

Table 3

Effect of Single-step Calcination(950°C, 2hrs) on Density and Dielectric

Properties of 0.9PMN-0.1 PT Dielectrics

Example 4

PbO(1.0mol:99.9% purity, Aldrich Chemical Co., USA), Nb₂O₅(0.3mol: 99.5% purity, Aldrich Chemical Co., USA), TiO₂ (0.1 mol: anatase 99.9% purity,

Aldrich Chemical Co., USA) and Mg(NO₃)₂6H₂O (0.315mol: 98% purity, Aldrich Chemical Co., USA) were placed with isopropanol in a polypropylene bottle and ball milled with zirconia balls having a diameter of 5mm for 24 hrs and distilled water (2.5 mol) was added thereto, and then the mixture was additionally ball milled for 2 hrs and dried. The resultant powder was preformed and heat- treated at 850°C for 2 hrs to thereby obtain the PMN-PT powder having the 100% pure perovskite phase, studied by using XRD. The powder which had been calcined was treated in accordance with the method performed in Example 2 and sintered at 850°-950°C for 2 hrs. Single phase perovskite powders of 0.95PMN-0.05PT composition were prepared by the same procedure as the above. The properties of the sintered pellets are shown in Table 4.

Table 4

Effect of Single-step Calcination(950°C, 2hrs) on Density and Dielectric

Properties of different composition of (l-x)PMN-xPT

0.9PMN - 0.1 PT

Example 5

A PMN-PT precursor powder was preformed according to the same method as in Example 3 and calcined at 950°C for 2 hrs, for thus having the 100% pure perovskite phase. The resultant powder was added to an aqueous solution of Cu(NO₃)₂3H₂ O (3.0 mol%: 99% purity, Junsei Chemical Co., Japan), and then the mixture was ball milled with zirconia balls and isopropanol for 4 hrs and dried. The dried powder was sieved through a 100 mesh sieve and pressed into pellets under a pressure of 800kg/cm² using a mold having a diameter of 10 mm. The pellets were sintered at temperatures of 825°-900°C for 2 hrs. The properties of the sintered powder are shown in Table 5.

Table 5

Effect of CuO(3 mol%) Addition on Density and Dielectric Properties of Calcined

(1-x)PMN - xPT powder

(0.9 PMN - 0.1 PT)

Example 6

A PMN-PT precursor powder preformed according to the same method as in Example 3 was calcined at 850°C for 2 hrs, for thus having 98% of the perovskite phase. The resultant powder was added to an aqueous solution of Cu(NO₃)₂3H₂O (2.0 mol%), and then the mixture was ball milled with PbO of 2.0 mol%, zirconia balls and isopropanol for 4 hrs and dried. The dried powder which had been preformed was sieved through a 100 mesh sieve and pressed into pellets under a pressure of 800kg/cm² using a mold having a diameter of 10 mm. The pellets were sintered at temperatures of 850°-950°C for 2 hrs. Different compositions of (l-x)PMN-xPT were also prepared in the same way as the above. The properties of the sintered pellets are shown in Table 6.

Table 6

Effect of Sintering Temperature on Density and Dielectric Properties of Calcined

0.9PMN-0.1 PT Powder with additive CuO(2 mol%)

Example 7

A PMN-PT precursor powder preformed according to the same method as in Example 3 was calcined at 850°C for 2 hrs, for thus having 100% of the perovskite phase. The resultant powder was added to an aqueous solution of Cu(NO₃)₂3H₂O (3.0 mol%: 99% purity, Junsei Chemical Co., Japan), and then the mixture was ball milled with PVA, zirconia balls and isopropanol for 4 hrs and dried. The dried powder was sieved through a 100 mesh sieve and pressed into pellets under a pressure of 800kg/cm² using a mold having a diameter of 10 mm. The pellets were sintered at a temperature of 825°-900°C for 2 hrs. The properties of the sintered powder are shown in Table 7.

Table 7

Effect of Sintering Temperature on Density and Dielectric Properties of One

Step-Calcined 0.9PMN-0.1 PT Powder With Additive CuO(3 mol%)

Example 8

A PMN-PT precursor powder preformed according to the same method as in Example 2 was calcined at 850°C for 2 hrs, for thus having 100% of the perovskite phase. The resultant powder was added to an aqueous solution of Cu(NO₃)₂3H₂O (3.0 mol%: 99% purity, Junsei Chemical Co., Japan), and then the mixture was ball milled with 0.5 wt% of PVA, zirconia balls in isopropanol for 4 hrs and dried. The dried powder was sieved through a 100 mesh sieve and pressed into pellets under a pressure of 800kg/cm² using a mold having a diameter of 10 mm. The pellets were sintered at temperatures of 825°-900°C for 2 hrs. The properties of the sintered pellets are shown in Table 8. Table 8

Effect of Sintering Temperature on Density and Dielectric Properties of Two

Step-Calcined 0.9PMN-0.1PT Powder With Additive CuO(3 mol%)

It will be apparent to those skilled in the art that various modifications and variations can be made in the preparation method for the low-temperature- sinterable Pb-based perovskite dielectric powder of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims

1. A preparation method for perovskite PMN dielectric powder, comprising: mixing PbO powder with Nb₂O₅ powder; 5 adding a solution in which Mg²⁺ is dissolved to a slurry of the resultant mixture; obtaining a PMN (Pb(Mg_1/3Nb_2/3)O₃) precursor powder by removing the solvent from the above solution; and calcining the precursor powder at 800°-950°C and sintering the calcined o powder.

2. The method according to claim 1 , wherein the solution is an aqueous solution or alcoholic aqueous solution.

5 3. A preparation method for perovskite PMN-PT dielectric powder, comprising: mixing PbO with Nb₂O₅ powder; adding a solution in which Mg²⁺ is dissolved to a slurry of the resultant mixture; 0 obtaining a PMN (Pb(Mg_1/3Nb_2/3)O₃) precursor powder by removing the solvent from the above solution; obtaining a PMN-PT [(1-x)Pb(Mg_1/3Nb_2/3)O₃-xPbTiO₃] precursor powder by mixing the above PMN precursor with PbTiO₃ powder and drying the mixture; and 5 calcining the PMN-PT precursor powder at 750°-950°C and sintering the calcined powder.

4. The method according to claim 3, wherein x ranges up to 0.1.

0 5. The method according to claim 3, wherein the solution is an aqueous solution or alcoholic aqueous solution.

6. The method according to claim 3, wherein the PbTiO₃is in the form of a single-phase tetragonal powder obtained by precipitating an aqueous solution of TiCI₄ over a slurry of PbO, and filtering, washing and drying the precipitate, and then heat-treating the dried precipitate at 500°-600°C.

7. The method according to claim 3, wherein after calcining the PMN-PT precursor powder a solution in which 2-5 mol% of Cu²⁺ is dissolved is added to the calcined powder.

8. The method according to claim 3, wherein a solution in which 2-5 mol% of Cu²⁺ is dissolved is added before calcining the PMN-PT precursor powder.

9. The method according to claim 7, wherein the solution is an aqueous solution or alcoholic solution.

10. The method according to claim 8, wherein the solution is an aqueous solution or alcoholic solution.

11. A preparation method for perovskite PMN-PT dielectric powder, comprising: mixing PbO, Nb₂O₅ and TiO₂ powder; adding a solution in which Mg ⁺ is dissolved to a slurry of the resultant mixture; obtaining a PMN-PT precursor powder by removing the solvent from the solution; and calcining the precursor powder at 800°-950°C and sintering the calcined powder.

12. The method according to claim 11 , wherein the solution is an aqueous solution or alcoholic solution.

13. The method according to claim 11 , wherein after calcining the PMN- PT precursor powder a solution in which 2-5 mol% of Cu²⁺is dissolved is added to the calcined powder.

14. The method according to claim 11 , wherein a solution in which 2-5 mol% of Cu²⁺ is dissolved is added before calcining the PMN-PT precursor powder.

15. The method according to claim 13, wherein the solution is an aqueous solution or alcoholic solution.

16. The method according to claim 14, wherein the solution is an aqueous solution or alcoholic solution.

AMENDED CLAIMS

[received by the International Bureau on 21 February 2000 (21 .02 .00); original claims 1, 3 and 11 amended ; remaining claims unchanged (3 pages)]

1. A preparation method for perovskite PMN dielectric powder, comprising: mixing PbO powder with Nb₂O₅ powder; adding a solution in which Mg²⁺ is dissolved to a slurry of the resultant mixture; obtaining a PMN (Pb(Mg₁3Nb2/3)O₃) precursor powder by removing the solvent from the above solution; and calcining the precursor powder at 800°C-950°C and sintering the calcined powder at 850°C-950°C.

3. A preparation method for perovskite PMN-PT dielectric powder, comprising: mixing PbO with Nb₂O₅ powder; adding a solution in which Mg²⁺ is dissolved to a slurry of the resultant mixture; obtaining a PMN (Pb(Mgι 3Nb₂/3)0₃) precursor powder by removing the solvent from the above solution; obtaining a PMN-PT [(1-x)Pb(Mgι_/3Nb_2/3)θ₃-xPbTi0₃] precursor powder by mixing the above PMN precursor with PbTiO₃ powder and drying the mixture; and calcining the PMN-PT precursor powder at 750°C-950°C and sintering the calcined powder at 825°C-950°C.

4. The method according to claim 3, wherein x ranges up to 0.1.

5. The method according to claim 3, wherein the solution is an aqueous solution or alcoholic aqueous solution.

6. The method according to claim 3, wherein the PbTiO₃ is in the form of a single-phase tetragonal powder obtained by precipitating an aqueous solution of TiCU over a slurry of PbO, and filtering, washing and drying the precipitate, and then heat-treating the dried precipitate at at 500°C-600°C.

7. The method according to claim 3, wherein after calcining the PMN-PT precursor powder a solution in which 2-5 mol% of Cu ⁺ is dissolved is added to the calcined powder.

11. A preparation method for perovskite PMN-PT dielectric powder, comprising: mixing PbO, Nb₂0₅ and TiO₂ powder; adding a solution in which Mg²⁺ is dissolved to a slurry of the resultant mixture; obtaining a PMN-PT precursor powder by removing the solvent from the solution; and calcining the precursor powder at at 800°C-950°C and sintering the calcined powder at 825°C-950°C.

13. The method according to claim 11 , wherein after calcining the PMN-PT precurs 3oorr ppoowwddeerr aa ssolution in which 2-5 mol% of Cu²⁺ is dissolved is added to the calcined powder.

14. The method according to claim 11 , wherein a solution in which 2-5

mol% of Cu²⁺ is dissolved is added before calcining the PMN-PT precursor powder.

AMENDED SHEETφflTTClJ.: 19) STATEMENT UNDER ARTICLE 19 (1)

This application contains sixteen (16) claims, currently claims 1-16 are pending in this application. The International Search Report cited three documents as relevant to the present application: two documents were cited in the "X" and "Y" category, one in the "X" category.

In view of cited references US 5,030,604(cited in the "X" and "Y" category) and JP 2- 252,623 (cited in the "X" category), claims 1, 3, and 11 are amended to distinguish the present invention over the cited references. US 5,030,604 relates to a preparation process for PMZN which requires calcining in twice and sintering temperatures of 950°C -1200°C. JP 2-252,623 relates to a preparation process for PMN-PT which further comprises the steps of precipitating, filtering and cleansing, and requires sintering temperatures of 900°C -1300°C. In the present invention, a simple process for preparing PMN and PMN-PT is provided and the step of sintering is performed at lower temperatures of 825°C to 950°C.

The detailed description of US 5,011,803(cited in the "X" and "Y" category) only discloses a process which comprises the steps of slurring, milling, drying, calcining, additional slurring and milling, fabricating into sheets, and sintering, while the present invention recites a simple process comprising the steps of slurring, milling, drying, calcining, and sintering.

Accordingly, it is believed the amendments to the claims will distinguish the present claims from the cited references. In addition, the present invention will not be invented in view of the cited references by a person of ordinary skill in the art.