PIEZOELECTRIC CERAMIC PRODUCTION

Abstract: A piezoelectric ceramic having high electromechanical coupling factor is prepared by heat treatment, at a tempera­ ture of from 500°C to 1050°C for 0.5 to 60 hours, a sintered ceramic of the composition: I. (1-w) (PbTi 1-z Zr z O₃) + wMnO₂, wherein 0.004 ≦ w ≦ 0.06, 0.48≦ z ≦ 0.64, and up to 10 atomic % of Pb may be replaced by one or more of Sr, Ca and Ba, or II. Pb ([B₁] A Nb 1-A ) O₃-PbTiO₃-PbZrO₃ with MnO₂, Pb ([B₂] B Nb 1-B ) O₃ - Pb ([B₃] c Nb 1-c ) O₃ - PbTiO₃ - PbZrO₃ with MnO₂, Pb(Mn 1/3 Nb 2/3 ) O₃ - PbTiO₃ - PbZrO₃, or Pb ([B₄] D Nb 1-D ) O₃ - Pb (Mn ₁/₃ Nb ₂/₃ ) O₃ - PbTiO₃- PbZrO₃, wherein B₂ ≠ B₃, each of B₁,B₂,B₃ and B₄ is one or more of Mg, Zn, Cd, Sn, Fe, Co and Ni when A, B, C and D = 1 / 3, and Li and/or Cu when A, B, C and D = 1 / 4, and up to 20 atomic % of Pb may be replaced by one or more of Sr, Ca and Ba.

Description: Piezoelectric ceramic production This invention is concerned with a method of preparing piezoelectric ceramics, particularly such ceramics having high piezoelectric response for use in, for example, ultrasonic transducers and ceramic filters. Lead titanate-lead zirconate ceramics, ternary system Pb (Mg1/3Nb2/3) O3 - PbTiO3 - PbTiO3 - PbZrO3 ceramics and quaterary system Pb ( Zn1/3Nb2/3) O3 1/3 2/3 3 Pb (Sn1/3Nb2/3) O3 - PbTiO3 - PbZrO3 ceramics have been used as piezoelectric ceramics. These piezoelectric ceramics are commonly made by sintering of the appropriate ceramic composition and then. polarizing the material by applying a D.C. voltage so as to impart electromechanical transducing properties thereto. It would be desirable to provide piezoelectric ceramics of improved electromechanical coupling factor to obtain higher piezoelectric response, but it is difficult to make much imprevement by refining the composition. We have no developed a method of preparing a piezoelectric ceramic material having a high electro- mechanical coupling factor, which comprises heat treating at a temperature of from 500 C to 1050 C for 0.5 to 60 hours, a sintered ceramic material of the composltion: I. ( 1 - w) (PbTi1-zZrzO3 ) + wMnO2, wherein 0.004 # w # 0.06, 0.48 < z # 0.64, and up to 10 atomic 0A of Pb may be replaced by one or more of Sr, Ca and Ba, or II. Pb ([B1]A Nb1-A) O3-PbTiO3 Pb (B2]B Nb1-B) O3 - Pb ([B3]cNb1-c) O3 - PbtiO3 PbZrO with MnO21 3 Pb ( Mnl/3Nb2/3 ) 03 - PbTiO3 - PbZrO3, or Pb ( [ 8 D Nbl,D) O3 - Pb (Mn1/3Nb2/3 ) 03 - PbTiO3 PbZrO3, wherein B2 + B3, each of B1, B, B3 and B4 is one or more of Mg, Zn, Cd, Sn, Fe, Co and Ni when A, B, C and D = 1/3 , and Li and/or Cu when A, B, C and D = X , and up to 20 atomic ,' of Pb may be replaced by one or more of Sr, Ca and Ba. The resulting piezoelectric ceramics have much higher electromechanical coupling factors than one which have not been heat treated. The sintered ceramic material used in the method according to the invention is preferably made by mixing the ingredients in appropriate (weighed) proportions, calcining the mixture, pulverizing the calcined material, shaping the powder thus obtained, and then sintering the shaped body. Before calcining, the ingredients may be mixed in the wet in a ball mill and then filtored and dried. The calcined material may be pulverized by wet-grinding, followed by filtering and drying. The sintering may be effected without pressing cr with hot-pressing, for example, at a temperatnre of 1050 to 1300 C and a pressure of 100 to 503 kg/cm2 for 0.5 to 24 hours. Such hot-press sintering conditions are suitable for obtaining ceramics of high mechanical strength. In order that the present invention may be more fully understood, the following Examples are given by way of illustration only. In the Examples, reference will be made to the accompanying drawings, in which: Figures 1 and 2 are graphs showing the relationship between the coupling factor kt and z in ceramic compositions prepared by the method according to the invention; and Figures 3 and 4 are gripes showing the relationship between the mechanical quality factor QM and w in ceramic compositions prepared by the method according to the invention. Example 1 Ceramics of the formula E ( 1 - w ) ( PbTi1-z ZrzO3) + wMnO2 ]. wherein 0.48 # z # 0.64 and 0.004 # w # 0.06 and one or more of Sr, Ca and Ba may be replaced by up to 10 ,4 of Pb. were produced as follows. PbO, TiO2, ZrO2, MnO2 and SrCO3 were weighed in the proportions of [ 0.992 ( Pb0.95Sr0.05Ti0.44Zr0.56O3 ) + 0.008 MnO@] and [0.984 (PbTiO 44 ZrO 56O3) + 0.016 MnO@] (these being specific examples of the above formula). The mixtures were wet-mixed for 17 hours in a ball-mill and the slurries obtained were filtered, dried and then calcined at about 8500C for 2 hours. The resulting materials were wet ground, filtered, dried and then shaped into discs having a diameter of 13 mm and a thickness of 1 mm by compressing at a pressure of 500 kg/cm2. The discs were sintered for 1 hour at 12800C for the former composition and 12600C for the latter composition. The sintered discs were then heat treated at 500 to 10500C for C.5 tu 60 hours in air atmosphere and the resulting ceramic discs were polished into discs having a thickness of 0.3 mm as one kind of specimer. As another kind of specimen, the obtained ceramic discs were cut off into rods of dimensions 5 x 1 x 1 mm3. After having gold electrodes attached thereto, the specimens were subjected to a DC field of 3 to 5 kV/mm for 30 minutes in a silicone oil at a temperature of 160 0C. The resulting specimens had electromechanical coupling factors kt and k33 (measured at room temperature) as shown in Tables 1 and 2. The corresponding properties of not heat-treated specimens are also given in the Tables for comparison. Table 1 EMI5.1 <tb> Heat <SEP> treatment <SEP> Coupling <SEP> factor <tb> <SEP> Temp. <SEP> Time <SEP> kt <SEP> k33 <tb> <SEP> ( C) <SEP> (hr) <tb> <SEP> no <SEP> heat <SEP> treatment <SEP> 0.50 <SEP> 0.61 <tb> <SEP> 500 <SEP> 60 <SEP> 0.52 <SEP> 0.62 <tb> <SEP> 600 <SEP> 24 <SEP> 0.53 <SEP> 0.64 <tb> <SEP> 700 <SEP> 4 <SEP> 0.54 <SEP> 0.68 <tb> <SEP> 700 <SEP> 60 <SEP> 0.56 <SEP> 0.71 <tb> <SEP> 800 <SEP> 4 <SEP> 0.56 <SEP> 0.71 <tb> <SEP> 900 <SEP> 4 <SEP> 0.58 <SEP> 0.72 <tb> <SEP> 1000 <SEP> 0.5 <SEP> 0.57 <SEP> 0.70 <tb> <SEP> 1000 <SEP> 4 <SEP> 0.57 <SEP> 0.67 <tb> <SEP> 1050 <SEP> 0.5 <SEP> 0.55 <SEP> 0.64 <tb> Composition: 0.992 (Pb0.95Sr0.06Ti0.44Zr0.56O3) + 0.008 MnO2 Table 2 EMI5.2 <tb> <SEP> Heat <SEP> treatment <SEP> # <SEP> <SEP> Coupling <SEP> factor <tb> Temp. <SEP> Time <SEP> kt <SEP> k33 <tb> <SEP> ( C) <SEP> (hr) <tb> no <SEP> heat <SEP> treatment <SEP> 0. <SEP> 48 <SEP> 0. <SEP> 58 <tb> <SEP> 500 <SEP> 60 <SEP> 0.49 <SEP> 0. <SEP> 60 <tb> <SEP> 700 <SEP> 24 <SEP> 0. <SEP> 52 <SEP> 0. <SEP> 63 <tb> <SEP> 900 <SEP> 4 <SEP> 0. <SEP> 55 <SEP> 0. <SEP> 67 <tb> <SEP> 900 <SEP> 12 <SEP> 0.55 <SEP> 0.68 <SEP> <tb> <SEP> 1000 <SEP> 1 <SEP> 0.53 <SEP> 0.65 <tb> <SEP> 1050 <SEP> 0.5 <SEP> !).52 <SEP> 0.62 <tb> Composition: 0.984(PbTi0.44Zr0.56O3) + 0.016 MnO2 To examine the influence of the values of z on the coupling factor kt, various ceramics of the formula [0.002 (Pb0.95 Ba0.05Til-zZrzO3) + 0.008 MnO2] were prepared with different values of z. The ceram were sintered at 1280 C and then heat treated at 900 for 4 hours, as described above. The relation between the coupling factor k and the value of z of the resulting specimens is illustrated in Figure 1, from which it can be seen that kt has a maximum value when z = 0.56 and a relatively high value when z is from o.48 to 0.64. To examine the influence of the value of w on the mechanical quality factor QM, ceramics of the formula C ( 1 - w ) ( Pb0.9Ca0.1Ti0.4Zr0.6O3 ) + wMnO2 ] were prepared with different values of w. The ceramics were sintered at 1280 C and heat treated at 9000C for 4 hours as described above. The relation between the mechanical quality factor QM and the value of w of the resulting specimens is illustrated in Figure 3, from which it can be seen that QM has a maximum value when w = 0.02 and is more than 200 when w is from 0.004 to 0.06. When Sr, Ba or Ca replaced more than 10 atomic of of the Pb, the kt value decreased remarkably, Example 2 Ceramics having the same formulae as in Example 1 i.e., EO.992 ( Pb0.95Sr0.05Ti0.44Zr0.56O3) + 0.008MnO@] and [0.984 (PbTi@ 44Zr@ @@O@) + 0.016MnO@ ] were produced. The raw materials were wet-mixed for 17 hours in a ball mill and the slurries obtained were filtered, dried and then calcined at about 8500C for 2 hours. The resulting materials were wet-ground, filtered and dried and ther shaped into discs having a diameter of 30 mm and thickness of 17 mm under a 2 pressure of 500 kg/cm . The discs were hot-press sintered at a temperature of 1250 0C and a pressure of 2 200 kg/cm for 4 hours. The sintered discs were cut into discs of diameter 8 mm and thickness 0.3 mm and rods having the dimensions of 5 x 1 x 1 mm3. These discs and rods were heat treated at 500 to 1500C for 0.5 to 60 hours. Gold electrodes were attached thereto and the samples were subjected to a DC field of 3 to 5 kV/mm for 30 minutes in a silicone oil at a temperature of 160 C. The resulting specimens had electromechanical coupling factors k and k33 (measured at room temperature) as shown in Tables 3 and 4. The corresponding properties of not heat-treated specimens are also given in the Tables for comparison. Table 3 EMI8.1 <tb> <SEP> Heat <SEP> Treatment <tb> Temp. <SEP> ( C) <SEP> Time <SEP> (hr) <SEP> kt <SEP> k33 <tb> <SEP> 500 <SEP> 60 <SEP> 0. <SEP> 53 <SEP> 0. <SEP> 63 <tb> <SEP> 600 <SEP> 24 <SEP> 0. <SEP> 54 <SEP> 0. <SEP> 65 <tb> <SEP> 700 <SEP> 4 <SEP> 0. <SEP> 54 <SEP> 0. <SEP> 64 <SEP> <tb> <SEP> 700 <SEP> 60 <SEP> 0. <SEP> 56 <SEP> 0. <SEP> 68 <tb> <SEP> 800 <SEP> 4 <SEP> 0.56 <SEP> 0.71 <tb> <SEP> 900 <SEP> 4 <SEP> 0.57 <SEP> 0.71 <tb> <SEP> 1000 <SEP> 0.5 <SEP> 0.57 <SEP> 0.70 <tb> <SEP> 1000 <SEP> 4 <SEP> 0.56 <SEP> 0.69 <tb> <SEP> 1050 <SEP> 0.5 <SEP> 0.53 <SEP> 0.64 <tb> no <SEP> heat <SEP> treatment <SEP> 0. <SEP> 51 <SEP> 0. <SEP> 62 <tb> Composition: 0.992 (Pb0.95Sr0.05Ti0.44Zr0.56O3) + 0.008MnO2 Table 4 EMI8.2 <tb> <SEP> Heat <SEP> Treatment <tb> Temp. <SEP> ( C) <SEP> Time <SEP> (hr) <SEP> kt <SEP> k33 <tb> <SEP> 500 <SEP> 60 <SEP> 0.49 <SEP> C. <SEP> 57 <SEP> <tb> <SEP> 700 <SEP> 24 <SEP> 0.51 <SEP> 0.59 <tb> <SEP> 900 <SEP> 4 <SEP> 0. <SEP> 54 <SEP> 0. <SEP> 64 <tb> <SEP> 900 <SEP> 12 <SEP> 0.54 <SEP> 0.65 <tb> <SEP> 1000 <SEP> 1 <SEP> 0.52 <SEP> 0.62 <tb> <SEP> 1050 <SEP> 0.5 <SEP> 0.50 <SEP> 0.59 <tb> no <SEP> heat <SEP> treatment <SEP> 0.48 <SEP> 0.56 <tb> Composition: 0.984 (PbTi0.44Zr0.56O3) + 0.016MnO2 To examine the influence of the values of z on the coupling factor kt, various ceramics of the formula [0.992 (Pb0.95Ba0.95Ti@.@Zr@O3) + 0.008MnO@] were prepared with different values of z. The ceramics wee were hot-press sintered at 1250 C and a pressure of 200 kg/cm2 for 4 hours and then heat treated at 900 C for 4 hours, as described above, The relation between the coupling factor kt and the value of z is illustrated in Figure 2, from which it can be seen that kt has a maximum value when z = 0.56 and a relatively high value when z is in the range from 4.8 to 0.64. To examine the influence of the value of w or the mechanical quality factor SIX ceramics of the formula [ (1 - w) (Pb@ @Ca@ @Ti@.4Zr@6O3) + wMnO2] were prepared with different values of w. The ceramics were hot-press sintered at 1250 C and a pressure of 200 kg/cm2 for 4 hours ad then heat treated at 900 C for 4 hours, as described above. The relation between the mechanical quality factor Qm and the value of w of thc resulting specimens is illustrated in Figure 4, from which it can be seen that QM has a maximum value when w = 0.02 and is more than 200 when w is from 0.004 to 0.06. When Sr, Ca or Ba replaced more than 10 atomic % of the Pb, the kt value decreased remarkably. Example 3 As raw inaterials, PbO, TiO2, ZrO2, MnO2, SrCO3, BaCO3, MgO, ZnO, NiO, CoO, SnO2, Li2CO3 and Nb2O5 were weighed respectively according to the compositions as indicated in Table 5. Each mixture was wet-mixed, filtered, clried and then calcined at about 8500C for 2 hours. The calcined materials were pulverized and shaped into discs of diameter 13 mm and thickness of 1 mm and also into discs of diameter 30 mm and thickness 17 mm. Then the former discs were sintered at 1250 to 100C for 60 minutes without pressure, and the latter discs wore hot-press sintered at 1250 0C and a pressure of 2 200 kg/cm for 4 hours. All the ceramic discs were then heat treated at 500 to 1050 C for 0.5 to 60 hours. After the heat treatment, the former discs (which were not presssintered) were polished to a thickness of 0.3 mm and the latter discs (which wc-re hot-press sintered) were cut into discs of diameter 8 mm and thickness 0.3 mm. Gold electrodes were attached thereto and a DC field of 3 to 5 kVjmm was applied for 30 minutes in a silicone oil at a temperature of 100 C. The resulting specimens had electromechanical coupling factors k and kt (measured p kt at room temperature) as shown in Table 5. The corres po:idin properties of not heat-treated specimens are also given in the Table for comparison. EMI11.1 ----------------------------------------------------------------------------------------------------------- <SEP> Compositons <SEP> Sintering <SEP> Conditions <SEP> Heat <SEP> Tratment <tb> <SEP> ------------------------------------------------------------------- <SEP> Temp. <SEP> Pressure <SEP> Time <SEP> Temp. <SEP> Time <tb> <SEP> ( C) <SEP> (Kg/cm2) <SEP> (hr) <SEP> ( C) <SEP> (hr) <SEP> kp <SEP> kt <tb> ----------------------------------------------------------------------------------------------------------- Pb <SEP> (Mg1/3Nb2/3)0.06Ti0.46Zr0.48O3 <SEP> 1250 <SEP> - <SEP> 1 <SEP> no <SEP> trentment <SEP> 0.55 <SEP> 0.46 <tb> + <SEP> 0.5 <SEP> Wt%MnO2 <SEP> -------------------------------- <SEP> 900 <SEP> 4 <SEP> 0.57 <SEP> 0.49 <tb> ----------------------------------------------------------------------------------------------------------- Pb0.95Sr0.05 <SEP> (Zn1/3Nb2/3)0.09 <SEP> (Sn1/3Nb2/3)0.09- <SEP> no <SEP> treatment <SEP> 0.55 <SEP> 0.48 <tb> Ti0.42Zr0.40O3 <SEP> + <SEP> 0.25 <SEP> wt <SEP> % <SEP> MnO2 <SEP> --------------------------------- <SEP> 1280 <SEP> - <SEP> 1 <SEP> 500 <SEP> 60 <SEP> 0.56 <SEP> 0.49 <tb> <SEP> --------------------------------- <SEP> 700 <SEP> 24 <SEP> 0.57 <SEP> 0.51 <tb> <SEP> ---------------------------------- <SEP> 900 <SEP> 4 <SEP> 0.59 <SEP> 0.52 <tb> <SEP> ---------------------------------- <SEP> 1050 <SEP> 0.5 <SEP> 0.57 <SEP> 0.50 <tb> ------------------------------------------------------------------------------------------------------------ Pb <SEP> (Zn1/3Nb2/3)0.06 <SEP> (Mn1/3Nb2/3) <SEP> 0.06Ti0.44- <SEP> 1250 <SEP> - <SEP> 1 <SEP> no <SEP> treatment <SEP> 0.55 <SEP> 0.48 <tb> Zr0.44O3 <SEP> ---------------------------------- <SEP> 800 <SEP> 8 <SEP> 0.58 <SEP> 0.51 <tb> ------------------------------------------------------------------------------------------------------------ Pb0.9Sr0.1 <SEP> (Li1/4Nb3/4)0.08Ti0.46Zr0.48O3 <SEP> + <SEP> no <SEP> treatment <SEP> 0.58 <SEP> 0.48 <tb> 0.5 <SEP> wt. <SEP> % <SEP> MnO2 <SEP> ----------------------------------- <SEP> 1250 <SEP> 200 <SEP> 4 <SEP> 1000 <SEP> 1 <SEP> 0.59 <SEP> 0.50 <tb> ------------------------------------------------------------------------------------------------------------- Pb <SEP> (Zn1/3Nb2/3) <SEP> 0.125Ti0.435Zr0.440O3 <SEP> + <SEP> 1250 <SEP> 200 <SEP> 4 <SEP> no <SEP> treatment <SEP> 0.48 <SEP> 0.44 <tb> 1 <SEP> wt. <SEP> %MnO2 <SEP> ----------------------------------- <SEP> 700 <SEP> 60 <SEP> 0.50 <SEP> 0.47 <tb> ------------------------------------------------------------------------------------------------------------- Pb <SEP> (Mn1/3Nbn2/3)0.06Ti0.4Zr0.48O3 <SEP> 1250 <SEP> 200 <SEP> 4 <SEP> no <SEP> treatment <SEP> 0.57 <SEP> 0.49 <tb> <SEP> ----------------------------------- <SEP> 900 <SEP> 4 <SEP> 0.59 <SEP> 0.51 <tb> ------------------------------------------------------------------------------------------------------------- Pb0.9Ba0.1 <SEP> (Ni1/3Nb2/3) <SEP> 0.06(Co1/3Nb2/3)0.06- <SEP> no <SEP> treatment <SEP> 0.54 <SEP> 0.45 <tb> <SEP> ------------------------------------ Ti0.44Zr0.4403 <SEP> + <SEP> 0.5 <SEP> wt. <SEP> % <SEP> MnO2 <SEP> 1250 <SEP> 200 <SEP> 4 <SEP> 900 <SEP> 4 <SEP> 0.56 <SEP> 0.47 <tb> ------------------------------------------------------------------------------------------------------------- Table 5 As apparent from Examples 1 to 3, the coupling factors kt and k33 of piezoelectric ceramics are remarkably increased by heat treatment at 500 to 1050 C for 0.5 to 60 flours after sinterinSX Such effects of increasing coupling factor are especially remarkable in tlae case of lead titanate-lead zirconate ceramics modified with MnO2. Heat treatment at a temperature of less than 500 0C or above 1050 C, or for less than 0.5 hours does not improve the piezoelectricity, while heat treatment for mere than 6C hours produces not so much increase of effect and results in a low productivity.

Claims: CLAIMS 1. A method of preparing a piezoelactric ceramic material, characterised by heat treating at a temperature of from 5000C to 10500C for 0.5 to 60 hours, a sintered ceramic material of the composition: I. ( 1 - w ) (pBTil-zZrzO3 ) + wMnO2, wherein o.OC4 # 0.06, 0.48 # z#0.64, and up to 10 atomic % of Pb may be replaced by one or more of Sr, Ca and Ba, or II. Pb ([B1]A 1-A)O3 - PhTiO3 - PbZrO3 with MnO2, Pb ([B2]B Nbl-B)O3 - Pb ([B3]cNb1-C) O3 - PbTiO3 - PbZrO3 with MnO2, Pb (Mn1/3Nb2/3) O3 - PbTiO3 - PbZrO3, or Pb ; D Nbl-D) 03 - Pb (Mn1/3Nb2/3 ) 03 - PbTiO3 - PbZrO3, wherein B2 ; B3, each of Bz, B2, B3 and B4 is one or more of Mg, Zn, Cd, Sn, Fe, Co and Ni when A, B, C and D = 1/3 , and Li and/or Cu when A, B, C and D = X , and up to 20 atomic % of Pb may be replaced by one or more of Sr, Ca and Ba. 2. A method according to claim 1, characterised in that the sintered ceramic material is prepared by mixing ingredients in appropriate proportions, calcining the mixture, pulverizing the calcined material, shaping the powder thus obtained and then sinterinS said shaped body. 3. A method according to claim 1 or 2, in which the sintering is carried out for 0.5 to 24 hours at a temperature of 1050 to 1300 0C and a pressure of 100 to 500 kg/cm2.

Inventors: KAWASHIMA, SYUNICHIRO, NISHIDA, MASAMITSU, OUCHI, HIROMU, UEDA, ICHIRO
Applicants: MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1979
Main classification: C04B35
IPC codes: H01L41, C04B35