- Email: [email protected]
3)O3–0.45Pb(Zr0.3Ti0.7)O3 ceramics
Materials Letters 66 (2012) 153–155
Contents lists available at SciVerse ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Effects of Fe2O3 doping on the microstructure and piezoelectric properties of 0.55Pb (Ni1/3Nb2/3)O3–0.45Pb(Zr0.3Ti0.7)O3 ceramics Jianzhou Du, Jinhao Qiu ⁎, Kongjun Zhu, Hongli Ji, Xuming Pang, Jun Luo State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China
a r t i c l e
i n f o
Article history: Received 23 May 2011 Accepted 13 August 2011 Available online 26 August 2011 Keywords: Fe2O3 doping 0.55PNN-0.45PZT Ceramics Microstructure Electrical properties
a b s t r a c t 0.55Pb(Ni1/3Nb2/3)O3–0.45Pb(Zr0.3Ti0.7)O3(PNN–PZT) ceramics with different concentration of xFe2O3 doping (where x = 0.0, 0.8, 1.2, 1.6 mol%) were synthesized by the conventional solid state sintering technique. X-ray diffraction analysis reveals that all specimens are a pure perovskite phase without pyrochlore phase. The density and grain size of Fe-doped ceramics tend to increase slightly with increasing concentration of Fe2O3. Comparing with the undoped ceramics, the piezoelectric, ferroelectric and dielectric properties of the Fe-doped PNN–PZT specimens are significantly improved. Properties of the piezoelectric constant as high as d33 ~ 956 pC/N, the electromechanical coupling factor kp ~ 0.74, and the dielectric constant εr ~ 6095 are achieved for the specimen with 1.2 mol% Fe2O3 doping sintered at 1200 °C for 2 h. © 2011 Elsevier B.V. All rights reserved.
1. Introduction Lead-based piezoelectric ceramics with typical perovskite structures, represented by Pb(Zr,Ti)O3 (PZT), have been widely used as sensors, actuators, electrostrictive transducers due to their excellent piezoelectric properties [1,2]. Lead nickel niobate Pb(Ni1/3Nb2/3) (PNN) has been studied by many researchers since its discovery by Smolenskii and Agranovskaya in 1958. The crystal symmetry for pure PNN at room temperature is cubic symmetry Pm3m with a lattice parameter of a = 0.403 nm [3]. Recently, many piezoelectric ceramics compositions have been developed from ternary solid solution systems, such as Pb (Ni1/3Nb2/3)O3–Pb(Zr,Ti)O3 (PNN–PZT), Pb(Zn1/3Nb2/3)O3–Pb(Zr,Ti)O3, Pb(Mg1/3Nb2/3)O3–Pb(Zr,Ti)O3. By comparison, PNN–PZT ceramics materials received more attention because of better piezoelectric and electromechanical properties [4–7]. The PNN-PZT ceramics system has an ABO3 perovskite structure, where lead is located at the A sites and niobium, nickel, zirconium, and titanium are randomly distributed over the B sites [8]. For PZT-based ceramics, the proper element additive is an effective approach to enhance material properties for special application. The donor dopants such as La3+, Cd2+, Bi3+ (occupy A-site) or the acceptor dopants such as Fe3+, Mg 2+, Ni2+, Cu2+, Zn2+, In3+ (occupy B-site) can improve electrical properties of the PZT-based ceramics in the previous works [9–15]. Fe2O3 is one of the most interesting additives. Weston [16] and Li Jin [17] investigated the effects of the addition of iron oxide on the microstructure and electric properties of PZT ceramics.
⁎ Corresponding author. Tel./fax: + 86 25 84891123. E-mail address: [email protected] (J. Qiu). 0167-577X/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2011.08.038
They found that dielectric constant decreased and the mechanical quality factor increased with the concentration of iron oxide. The electromechanical and piezoelectric properties of Fe-doped PLZT, PMN-PZT, and BSPT ceramics have also been studied [9,18,19]. However, the effects of Fe2O3 doping on the physical properties of PNN–PZT ceramics have not been reported in the literature. In this work, the microstructures, piezoelectric, and ferroelectric properties of 0.55Pb(Ni1/3Nb2/3)O3–0.45Pb (Zr0.3Ti0.7)O3 with different concentrations of Fe2O3 doping were systematically investigated. 2. Experimental procedure Reagent-grade powders of PbO, NiO, Nb2O5, ZrO2, TiO2, and Fe2O3 were utilized as the raw materials, the 0.55Pb(Ni1/3Nb2/3)O3–0.45Pb (Zr0.3Ti0.7)O3–xFe2O3 (x =0.0, 0.8, 1.2, 1.6 mol%) ceramics were synthesized by a conventional solid state sintering technique. 1 wt.% PbO excess was taken to prevent the formation of pyrochlore phase during sintering process. After ball milling for 12 h, the dried mixtures were precalcined at 1050 °C for 4 h. The obtained powders were reground, pressed into disks with a diameter of 15 mm at 300 MPa, and sintered at 1200 °C for 2 h in a sealed alumina crucible. The bulk density of the ceramics was measured by the Archimedes method. After all specimens were polished, silver paste was fired on two major as electrodes. The samples were poled in 50 °C silicone oil bath by applying a DC electric field of 2 kV/mm for 30 min. The microstructure was observed by a scanning electron microscope (SEM, JMS-5610LV, Japan). The crystal structure was analyzed by an X-ray diffraction (XRD, D8 Advance, Bruker, Germany) with a Cu Kα radiation. The piezoelectric constant (d33) was measured by a quasi-static d33 meter (ZJ-3A, China). The ferroelectric and piezoelectric properties
154
J. Du et al. / Materials Letters 66 (2012) 153–155 Table 1 Electrical properties of the 0.55PNN–0.45PZT–xFe2O3 ceramics.
Fig. 1. XRD patterns of the 0.55PNN–0.45PZT–xFe2O3 ceramics.
were obtained by a ferroelectric analyzer system (TF2000, Germany) and a precision impedance analyzer (HP4294A, Japan), respectively.
3. Results and discussion Fig. 1 shows the XRD patterns of the 0.55PNN–0.45PZT–xFe2O3 ceramics (x = 0.0, 0.8, 1.2, 1.6 mol%) sintered at 1200 °C for 2 h. It can be seen that all specimens are a pure perovskite structure without pyrochlore phase or second phase. The XRD data show that the splitting of (200) peak is not observed, indicating that the major phase is pure PNN–PZT with pseudocubic symmetry. With increasing the concentration of Fe2O3x from 0.0 to 1.6 mol%, the (200) diffraction peaks slightly shift to a higher 2θ angle. The slight contraction of crystal grain can be deduced by Bragg's equation (2dsin θ = λ), the reason could be summarized as the ion substitute model. Fe ion exists mainly in the state of Fe3+ with ionic radius of 64.5 pm, which entered into ABO3 pervoskite structure of BO6 octahedron to substitute for the B-site ions (where, B = Ni3+, Nb 5+, Ti4+, Zr4+ with ionic radius of 69 pm, 69 pm, 60.5 pm, and 72 pm, respectively). The ionic radius of
x (mol)
Ec (kV/cm )
Pr (μC/cm2)
Np (Hz⋅m)
d33 (pC/N)
d31 (pC/N)
kp
εr
tanδ
0.0 0.8% 1.2% 1.6%
3.89 4.08 4.30 4.51
24.9 24.5 26.9 25.5
2013 1960 1933 1942
802 873 956 941
− 333 − 367 − 400 − 408
0.68 0.70 0.74 0.71
5362 5691 6095 6834
2.9% 2.8% 2.6% 2.8%
Fe 3+ is different from B-site ions, which can bring a litte distortion of the octahedron. Fig. 2 shows the SEM micrographs of 0.55PNN–0.45PZT ceramics with different concentration of Fe2O3 doping. The results indicate that the average grain size (d) gradually increases in the range of 2.5–6 μm with the increase of Fe2O3 content from x = 0.0 to 1.2 mol%, and the d decreases slightly with further increase of Fe2O3 content. The density reaches maximum value of 7.97 g/cm 3 for the sample with 1.2 mol% Fe2O3 doping. This phenomenon may be due to the improvement of sinterability and ‘size effect’ with the increase of Fe2O3 content. The ferroelectric polarization versus electric field (P–E) loops of 0.55PNN–0.45PZT–xFe2O3 ceramics were measured by TF2000 ferroelectric analyzer system at 10 Hz. Compared with the undoped sample, the Fe2O3-doped PNN–PZT specimens show the larger remanent porization (Pr) and coercive field (Ec) with the increase concentration of Fe2O3 as shown in Table 1. The specimen with 1.2 mol% addition shows higher values of Ec ~ 4.3 kV/cm, Pr ~26.9 μC/cm 2. This is probably due to the oxygen vacancies caused by the substitution of Fe3+ ions in the B-sites (acceptor dopant), which lead to an increase of internal bias field. This result is similar to that in the Fe-doped Pb(Zr,Ti)O3–Pb (Y2/3 W1/3)O3 ceramics [20]. Fig. 3 shows the temperature dependence of the relative permittivity (εr) for the 0.55PNN–0.45PZT–xFe2O3 (x = 0.0–1.6 mol%) ceramics at 1 kHz. As it can be seen, the Curie temperature (Tc) of pure 0.55PNN-0.45PZT is 113 °C, which is reasonable when considering that the Tc of PNN(− 120 °C), PZ(230 °C) and PT (490 °C). The results also show that the Tc increase (106 °C, 108 °C, and 120 °C)
Fig. 2. SEM micrographs of the 0.55PNN–0.45PZT–xFe2O3 ceramics.
J. Du et al. / Materials Letters 66 (2012) 153–155
155
for 2 h. All ceramics have the pure perovskite phase, and no pyrochlore phase or second phases detected. The addition of Fe2O3 is not only an effective sintering aid for improving the sinterability, but also an acceptor dopant for improving the piezoelectric properties of PNN–PZT ceramics. The optimized amount of Fe2O3 is x = 1.2 mol%, the values of ρ, d33, kP, εr, tanδ, Tc, and Pr are 7.97 g/cm3, 956 pC/N, 0.74, 6095, 2.6%, 108 °C, 26.9 μC/cm2, respectively. The high performance indicates that the Fe-doped PNN–PZT ceramics has potential applications as actuators or sensors.
Acknowledgment
Fig. 3. Temperature dependence of the relative permittivity for the 0.55PNN–0.45PZT– xFe2O3 ceramics.
with increasing Fe2O3 content (x = 0.8–1.6 mol%). The piezoelectric constants (d33, d31), frequency constant (Np), electromechanical coupling coefficient (kp), and dielectric constants (εr) are summarized in Table 1. The Np decreases firstly from 2013 to 1933 and then increases to 1942. The variation of d33 are in agreement with the trend of kp, the maximum values of d33 ~ 956 pC/N and kp ~ 0.74 are achieved in the sample with 1.2 mol% Fe2O3, which is significantly improved compared with the pure 0.55PNN–0.45PZT ceramics with d33 ~ 802 pC/N and kp ~ 0.68. Hence, it is clear that the addition of Fe ions softens the materials and improves the coupling constant. Besides, the d31 and εr increase largely with the addition of Fe2O3, the maximum value of εr ~ 6834, d31 ~ −408 pC/N at x = 1.6 mol%. The tanδ of all samples are very low (b3%), the sample with x = 1.2 mol% shows the lowest value of 2.6%. The variation of the electrical properties is due to the complex effects of phase evolution, grain size, and oxygen vacancy caused by the addition of Fe2O3. 4. Conclusions This work investigated the effects of small amount xFe2O3 (x= 0.0– 1.6 mol%) additions on the microstructures and electrical properties of 0.55Pb(Ni1/3Nb2/3)O3–0.45Pb(Zr0.3Ti0.7)O3 ceramics sintered at 1200 °C
This work was supported by the 863 project (2007AA03Z104), the PAPD, NSFC (90923029), NSF of Jiangsu Province (BK2009020), the Program for Changjiang Scholars and Innovative Research Team in University (IRT0968), the Funding of Jiangsu Innovation Program for Graduate Education (CXZZ11-0194), the Funding for Outstanding Doctoral Dissertation in NUAA (BCXJ11-02), and NUAA Research Fund for Fundamental Research.
References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20]
Jaffe B, Roth RS, Marzullo S. J Appl Phys 1954;25:809–10. Bove T, Wolny W, Ringgaard E, Pedersen A. J Eur Ceram Soc 2001;21:1469–72. Smolenskii GA, Agranovskaya AI. Sov Phys Tech Phys 1958;2:1380–2. Wagner S, Kahraman D, Kungl H, Hoffmann MJ. J Appl Phys 2005;98:024102. Qiu J, Tani J, Yanada N, Kobayashi Y, Takahashi H. J Intell Mater Syst Struct 2004;15:643–53. Vittayakorn N, Rujijanagul G, Tan X, Marquardt MA, Cann DP. J Appl Phys 2004;96: 5103–9. Cao R, Li G, Zeng J, Zhao S, Zheng L, Yin Q. J Am Ceram Soc 2010;93:737–41. Cho JH, Park IK, Kim HG. J Am Ceram Soc 1997;80:1523–34. Rai R, Mishra S, Singh NK. J Alloy Comp 2009;487:494–8. Zhu XH, Xu J, Meng ZY. J Mater Sci 1997;32:4275–82. Gan BK, Yao K. Ceram Int 2009;35:2061–7. Liu J, Zhu J, Li X, Wang M, Zhu X, Zhu J, et al. Mater Lett 2011;65:948–50. Kim MS, Jeon S, Jeong SJ, Kim IS, Song JS. Electron Mater Lett 2008;4:189–92. Nahm CW. Mater Lett 2011;65:1299–301. Miclea C, Tanasoiu C, Miclea CF, Amarande L, Gheorghiu A, Sima FN. J Eur Ceram Soc 2005;25:2397–400. Weston TB, Webster AH, Mcnamara VM. J Am Ceram Soc 1969;52:253–7. Jin L, He Z, Damjanovic D. Appl Phys Lett 2009;95:012905. Chen CY, Lin HL. Ceram Int 2004;30:2075–9. Winotai P, Udomkan N, Meejoo S. Sens Actuators A 2005;122:257–63. Yoon SJ, Joshi A, Uchino K. J Am Ceram Soc 1997;80:1035–9.
Contents lists available at SciVerse ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Effects of Fe2O3 doping on the microstructure and piezoelectric properties of 0.55Pb (Ni1/3Nb2/3)O3–0.45Pb(Zr0.3Ti0.7)O3 ceramics Jianzhou Du, Jinhao Qiu ⁎, Kongjun Zhu, Hongli Ji, Xuming Pang, Jun Luo State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China
a r t i c l e
i n f o
Article history: Received 23 May 2011 Accepted 13 August 2011 Available online 26 August 2011 Keywords: Fe2O3 doping 0.55PNN-0.45PZT Ceramics Microstructure Electrical properties
a b s t r a c t 0.55Pb(Ni1/3Nb2/3)O3–0.45Pb(Zr0.3Ti0.7)O3(PNN–PZT) ceramics with different concentration of xFe2O3 doping (where x = 0.0, 0.8, 1.2, 1.6 mol%) were synthesized by the conventional solid state sintering technique. X-ray diffraction analysis reveals that all specimens are a pure perovskite phase without pyrochlore phase. The density and grain size of Fe-doped ceramics tend to increase slightly with increasing concentration of Fe2O3. Comparing with the undoped ceramics, the piezoelectric, ferroelectric and dielectric properties of the Fe-doped PNN–PZT specimens are significantly improved. Properties of the piezoelectric constant as high as d33 ~ 956 pC/N, the electromechanical coupling factor kp ~ 0.74, and the dielectric constant εr ~ 6095 are achieved for the specimen with 1.2 mol% Fe2O3 doping sintered at 1200 °C for 2 h. © 2011 Elsevier B.V. All rights reserved.
1. Introduction Lead-based piezoelectric ceramics with typical perovskite structures, represented by Pb(Zr,Ti)O3 (PZT), have been widely used as sensors, actuators, electrostrictive transducers due to their excellent piezoelectric properties [1,2]. Lead nickel niobate Pb(Ni1/3Nb2/3) (PNN) has been studied by many researchers since its discovery by Smolenskii and Agranovskaya in 1958. The crystal symmetry for pure PNN at room temperature is cubic symmetry Pm3m with a lattice parameter of a = 0.403 nm [3]. Recently, many piezoelectric ceramics compositions have been developed from ternary solid solution systems, such as Pb (Ni1/3Nb2/3)O3–Pb(Zr,Ti)O3 (PNN–PZT), Pb(Zn1/3Nb2/3)O3–Pb(Zr,Ti)O3, Pb(Mg1/3Nb2/3)O3–Pb(Zr,Ti)O3. By comparison, PNN–PZT ceramics materials received more attention because of better piezoelectric and electromechanical properties [4–7]. The PNN-PZT ceramics system has an ABO3 perovskite structure, where lead is located at the A sites and niobium, nickel, zirconium, and titanium are randomly distributed over the B sites [8]. For PZT-based ceramics, the proper element additive is an effective approach to enhance material properties for special application. The donor dopants such as La3+, Cd2+, Bi3+ (occupy A-site) or the acceptor dopants such as Fe3+, Mg 2+, Ni2+, Cu2+, Zn2+, In3+ (occupy B-site) can improve electrical properties of the PZT-based ceramics in the previous works [9–15]. Fe2O3 is one of the most interesting additives. Weston [16] and Li Jin [17] investigated the effects of the addition of iron oxide on the microstructure and electric properties of PZT ceramics.
⁎ Corresponding author. Tel./fax: + 86 25 84891123. E-mail address: [email protected] (J. Qiu). 0167-577X/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2011.08.038
They found that dielectric constant decreased and the mechanical quality factor increased with the concentration of iron oxide. The electromechanical and piezoelectric properties of Fe-doped PLZT, PMN-PZT, and BSPT ceramics have also been studied [9,18,19]. However, the effects of Fe2O3 doping on the physical properties of PNN–PZT ceramics have not been reported in the literature. In this work, the microstructures, piezoelectric, and ferroelectric properties of 0.55Pb(Ni1/3Nb2/3)O3–0.45Pb (Zr0.3Ti0.7)O3 with different concentrations of Fe2O3 doping were systematically investigated. 2. Experimental procedure Reagent-grade powders of PbO, NiO, Nb2O5, ZrO2, TiO2, and Fe2O3 were utilized as the raw materials, the 0.55Pb(Ni1/3Nb2/3)O3–0.45Pb (Zr0.3Ti0.7)O3–xFe2O3 (x =0.0, 0.8, 1.2, 1.6 mol%) ceramics were synthesized by a conventional solid state sintering technique. 1 wt.% PbO excess was taken to prevent the formation of pyrochlore phase during sintering process. After ball milling for 12 h, the dried mixtures were precalcined at 1050 °C for 4 h. The obtained powders were reground, pressed into disks with a diameter of 15 mm at 300 MPa, and sintered at 1200 °C for 2 h in a sealed alumina crucible. The bulk density of the ceramics was measured by the Archimedes method. After all specimens were polished, silver paste was fired on two major as electrodes. The samples were poled in 50 °C silicone oil bath by applying a DC electric field of 2 kV/mm for 30 min. The microstructure was observed by a scanning electron microscope (SEM, JMS-5610LV, Japan). The crystal structure was analyzed by an X-ray diffraction (XRD, D8 Advance, Bruker, Germany) with a Cu Kα radiation. The piezoelectric constant (d33) was measured by a quasi-static d33 meter (ZJ-3A, China). The ferroelectric and piezoelectric properties
154
J. Du et al. / Materials Letters 66 (2012) 153–155 Table 1 Electrical properties of the 0.55PNN–0.45PZT–xFe2O3 ceramics.
Fig. 1. XRD patterns of the 0.55PNN–0.45PZT–xFe2O3 ceramics.
were obtained by a ferroelectric analyzer system (TF2000, Germany) and a precision impedance analyzer (HP4294A, Japan), respectively.
3. Results and discussion Fig. 1 shows the XRD patterns of the 0.55PNN–0.45PZT–xFe2O3 ceramics (x = 0.0, 0.8, 1.2, 1.6 mol%) sintered at 1200 °C for 2 h. It can be seen that all specimens are a pure perovskite structure without pyrochlore phase or second phase. The XRD data show that the splitting of (200) peak is not observed, indicating that the major phase is pure PNN–PZT with pseudocubic symmetry. With increasing the concentration of Fe2O3x from 0.0 to 1.6 mol%, the (200) diffraction peaks slightly shift to a higher 2θ angle. The slight contraction of crystal grain can be deduced by Bragg's equation (2dsin θ = λ), the reason could be summarized as the ion substitute model. Fe ion exists mainly in the state of Fe3+ with ionic radius of 64.5 pm, which entered into ABO3 pervoskite structure of BO6 octahedron to substitute for the B-site ions (where, B = Ni3+, Nb 5+, Ti4+, Zr4+ with ionic radius of 69 pm, 69 pm, 60.5 pm, and 72 pm, respectively). The ionic radius of
x (mol)
Ec (kV/cm )
Pr (μC/cm2)
Np (Hz⋅m)
d33 (pC/N)
d31 (pC/N)
kp
εr
tanδ
0.0 0.8% 1.2% 1.6%
3.89 4.08 4.30 4.51
24.9 24.5 26.9 25.5
2013 1960 1933 1942
802 873 956 941
− 333 − 367 − 400 − 408
0.68 0.70 0.74 0.71
5362 5691 6095 6834
2.9% 2.8% 2.6% 2.8%
Fe 3+ is different from B-site ions, which can bring a litte distortion of the octahedron. Fig. 2 shows the SEM micrographs of 0.55PNN–0.45PZT ceramics with different concentration of Fe2O3 doping. The results indicate that the average grain size (d) gradually increases in the range of 2.5–6 μm with the increase of Fe2O3 content from x = 0.0 to 1.2 mol%, and the d decreases slightly with further increase of Fe2O3 content. The density reaches maximum value of 7.97 g/cm 3 for the sample with 1.2 mol% Fe2O3 doping. This phenomenon may be due to the improvement of sinterability and ‘size effect’ with the increase of Fe2O3 content. The ferroelectric polarization versus electric field (P–E) loops of 0.55PNN–0.45PZT–xFe2O3 ceramics were measured by TF2000 ferroelectric analyzer system at 10 Hz. Compared with the undoped sample, the Fe2O3-doped PNN–PZT specimens show the larger remanent porization (Pr) and coercive field (Ec) with the increase concentration of Fe2O3 as shown in Table 1. The specimen with 1.2 mol% addition shows higher values of Ec ~ 4.3 kV/cm, Pr ~26.9 μC/cm 2. This is probably due to the oxygen vacancies caused by the substitution of Fe3+ ions in the B-sites (acceptor dopant), which lead to an increase of internal bias field. This result is similar to that in the Fe-doped Pb(Zr,Ti)O3–Pb (Y2/3 W1/3)O3 ceramics [20]. Fig. 3 shows the temperature dependence of the relative permittivity (εr) for the 0.55PNN–0.45PZT–xFe2O3 (x = 0.0–1.6 mol%) ceramics at 1 kHz. As it can be seen, the Curie temperature (Tc) of pure 0.55PNN-0.45PZT is 113 °C, which is reasonable when considering that the Tc of PNN(− 120 °C), PZ(230 °C) and PT (490 °C). The results also show that the Tc increase (106 °C, 108 °C, and 120 °C)
Fig. 2. SEM micrographs of the 0.55PNN–0.45PZT–xFe2O3 ceramics.
J. Du et al. / Materials Letters 66 (2012) 153–155
155
for 2 h. All ceramics have the pure perovskite phase, and no pyrochlore phase or second phases detected. The addition of Fe2O3 is not only an effective sintering aid for improving the sinterability, but also an acceptor dopant for improving the piezoelectric properties of PNN–PZT ceramics. The optimized amount of Fe2O3 is x = 1.2 mol%, the values of ρ, d33, kP, εr, tanδ, Tc, and Pr are 7.97 g/cm3, 956 pC/N, 0.74, 6095, 2.6%, 108 °C, 26.9 μC/cm2, respectively. The high performance indicates that the Fe-doped PNN–PZT ceramics has potential applications as actuators or sensors.
Acknowledgment
Fig. 3. Temperature dependence of the relative permittivity for the 0.55PNN–0.45PZT– xFe2O3 ceramics.
with increasing Fe2O3 content (x = 0.8–1.6 mol%). The piezoelectric constants (d33, d31), frequency constant (Np), electromechanical coupling coefficient (kp), and dielectric constants (εr) are summarized in Table 1. The Np decreases firstly from 2013 to 1933 and then increases to 1942. The variation of d33 are in agreement with the trend of kp, the maximum values of d33 ~ 956 pC/N and kp ~ 0.74 are achieved in the sample with 1.2 mol% Fe2O3, which is significantly improved compared with the pure 0.55PNN–0.45PZT ceramics with d33 ~ 802 pC/N and kp ~ 0.68. Hence, it is clear that the addition of Fe ions softens the materials and improves the coupling constant. Besides, the d31 and εr increase largely with the addition of Fe2O3, the maximum value of εr ~ 6834, d31 ~ −408 pC/N at x = 1.6 mol%. The tanδ of all samples are very low (b3%), the sample with x = 1.2 mol% shows the lowest value of 2.6%. The variation of the electrical properties is due to the complex effects of phase evolution, grain size, and oxygen vacancy caused by the addition of Fe2O3. 4. Conclusions This work investigated the effects of small amount xFe2O3 (x= 0.0– 1.6 mol%) additions on the microstructures and electrical properties of 0.55Pb(Ni1/3Nb2/3)O3–0.45Pb(Zr0.3Ti0.7)O3 ceramics sintered at 1200 °C
This work was supported by the 863 project (2007AA03Z104), the PAPD, NSFC (90923029), NSF of Jiangsu Province (BK2009020), the Program for Changjiang Scholars and Innovative Research Team in University (IRT0968), the Funding of Jiangsu Innovation Program for Graduate Education (CXZZ11-0194), the Funding for Outstanding Doctoral Dissertation in NUAA (BCXJ11-02), and NUAA Research Fund for Fundamental Research.
References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20]
Jaffe B, Roth RS, Marzullo S. J Appl Phys 1954;25:809–10. Bove T, Wolny W, Ringgaard E, Pedersen A. J Eur Ceram Soc 2001;21:1469–72. Smolenskii GA, Agranovskaya AI. Sov Phys Tech Phys 1958;2:1380–2. Wagner S, Kahraman D, Kungl H, Hoffmann MJ. J Appl Phys 2005;98:024102. Qiu J, Tani J, Yanada N, Kobayashi Y, Takahashi H. J Intell Mater Syst Struct 2004;15:643–53. Vittayakorn N, Rujijanagul G, Tan X, Marquardt MA, Cann DP. J Appl Phys 2004;96: 5103–9. Cao R, Li G, Zeng J, Zhao S, Zheng L, Yin Q. J Am Ceram Soc 2010;93:737–41. Cho JH, Park IK, Kim HG. J Am Ceram Soc 1997;80:1523–34. Rai R, Mishra S, Singh NK. J Alloy Comp 2009;487:494–8. Zhu XH, Xu J, Meng ZY. J Mater Sci 1997;32:4275–82. Gan BK, Yao K. Ceram Int 2009;35:2061–7. Liu J, Zhu J, Li X, Wang M, Zhu X, Zhu J, et al. Mater Lett 2011;65:948–50. Kim MS, Jeon S, Jeong SJ, Kim IS, Song JS. Electron Mater Lett 2008;4:189–92. Nahm CW. Mater Lett 2011;65:1299–301. Miclea C, Tanasoiu C, Miclea CF, Amarande L, Gheorghiu A, Sima FN. J Eur Ceram Soc 2005;25:2397–400. Weston TB, Webster AH, Mcnamara VM. J Am Ceram Soc 1969;52:253–7. Jin L, He Z, Damjanovic D. Appl Phys Lett 2009;95:012905. Chen CY, Lin HL. Ceram Int 2004;30:2075–9. Winotai P, Udomkan N, Meejoo S. Sens Actuators A 2005;122:257–63. Yoon SJ, Joshi A, Uchino K. J Am Ceram Soc 1997;80:1035–9.