GUO Lin, QIAO Xianji, LI Xiuzhi, LONGXifa, HE Chao

Dielectric, Ferroelectric and Piezoelectric Properties of Pb(In1/2Nb1/2)O3-Pb(Ni1/3Nb2/3)O3-PbTiO3Ternary Ceramics near Morphotropic Phase Boundary

GUO Lin1,2, QIAO Xianji2, LI Xiuzhi2, LONGXifa2, HE Chao2

(1. College of Chemistry and Materials Science, Fujian Normal University, Fuzhou 350117, China; 2. Key Laboratory of Optoelectric Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China)

Lead-based complex perovskite ferroelectric materials have been widely used as electromechanical sensors, actuators, and transducers. Among them, Pb(Ni1/3Nb2/3)O3-PbTiO3(PNN-PT) based solid solution has been drawn much attentions of scientists for its excellent dielectric and piezoelectric properties near morphotropic phase boundary (MPB) region. However, the relatively high dielectric loss andlow Curie temperature near MPB region limited its application in high temperature and high power devices. In this work, Pb(In1/2Nb1/2)O3(PIN) was introduced into PNN-PT ceramics for improving their electrical properties and Curie temperature. The ternary ferroelectric ceramicsPb(In1/2Nb1/2)O3-Pb(Ni1/3Nb2/3)O3-PbTiO3were successfully prepared by a two-step synthesis process. All samples exhibited pure perovskite phase without any secondary phase. The structure transferred from rhombohedral to tetragonal phase with increasing PT content. The MPB phase diagram of ternary system at room temperature was established based on XRD results. The values of Curie temperature were improved significantly after PIN added into PNN-PT system. Importantly, the introduction of PIN into PNN-PT system can effectively reduce dielectric loss and conductivity. The ceramics in the MPB region exhibited excellent properties. 0.30PIN-0.33PNN-0.37PT ceramic was found to have optimal properties with33=417 pC/N,C=200 ℃,′= 3206,tan=0.033,r=33.5 μC/cm2andc=14.1 kV/cm at room temperature, respectively. The Curie temperature and piezoelectric coefficient were improved while dielectric loss and conductivity were reduced after the introduction of PIN into PNN-PT. The enhancements of piezoelectric properties and high Curie temperature make this ternary system a promising material for high power and high temperature transducer applications.

ferroelectric ceramics; morphotropic phase boundary; Curie temperature; piezoelectric properties

Lead-based complex perovskite ferroelectric materials Pb(B1,B2)O3-PbTiO3(B1=Mg2+, Zn2+, Ni2+, Sc3+, In3+, Lu3+, …, B2=Nb5+, Ta5+, W6+, …) have been widely used as electromechanical sensors, actuators, and transducers[1-2]. These systems near the morphotropic phase boundary (MPB) display outstanding piezoelectric and dielectric properties[3-4]. As a typical relaxor ferroelectrics, Pb(Ni1/3Nb2/3)O3-PbTiO3(PNN-PT) have attracted great attention due to its excellent dielectric constant (> 4000) and piezoelectric coeffiecient (33450 pC/N) nearMPB region[5-6]. On this basis, PNN-based binary and ter-nary systems, such as Pb(Ni1/3Nb2/3)O3-PbTiO3(PNN-PT)[7],Pb(Mg1/3Nb2/3)-Pb(Ni1/3Nb2/3)O3-PbTiO3(PMN-PNN-PT)[8], Pb(Zn1/3Nb2/3)O3-Pb(Ni1/3Nb2/3)O3-PbTiO3(PZN-PNN-PT)[9], which exhibit excellent electrical properties near the MPB compositions, have been reported. Although PNN- PT binary system has outstanding electrical properties, it has some drawbacks. Fistly, the relatively low electric po-larization intensity and high leakage current induced by the variable valence of Ni ions, following inferior pie-zoelectric coefficients[10]. Secondly, PNN-PT binary sys-tem exhibit relatively low Curie temperature near MPB region (120 ℃), which limit its application in high temperature[7-8,11]. Therefore, the addition of other compo-nent with high Curie temperature to PNN-PT system can improve electrical properties and Curie temperature, such as Pb(Lu1/2Nb1/2)O3-Pb(Ni1/3Nb2/3)O3-PbTiO3(PLN-PNN-PT), Pb(Ni1/3Nb2/3)O3-PbHfO3-PbTiO3(PNN-PH-PT) and Pb(Ni1/3Nb2/3)O3-Pb(Sc1/2Nb1/2)O3-PbTiO3(PNN-PSN-PT).These ternary systems have been confirmed to have high Cu-rie temperature and excellent piezoelectric properties[12-14].

As a member of Pb(B1,B2)O3system, Pb(In1/2Nb1/2)O3(PIN) has Curie temperature of about 90 ℃[15]. Furthermore, the solid solution of (1–)PIN-PT near its MPB exhibits high Curie temperatureC~ 300 ℃ and excellent piezoelectric properties (33=395 pC/N)[16-18]. For above purposes, the introduction of PIN into PNN-PT system may improve its Curie temperature and piezoelectric properties, and reduced conductivity. Therefore, in present work, PIN was introduced into the PNN-PT system to form a ternary system PIN-PNN-PT. Structure, MPB diagram, electrical properties of PIN-PNN-PT were investigated.

1 Experimental

Pb(In1/2Nb1/2)O3-(1––)Pb(Ni1/3Nb2/3)O3-PbTiO3(= 0.10, 0.30, 0.50) ceramics were prepared using a two- step synthesis process and raw materials of PbO, In2O3, NiO, Nb2O5and TiO2. First, the precursors of B-site ions were prepared using the columbite or wolframite method. InNbO4(IN) was calcined according to the stoichiometric proportions at 900 ℃ for 4 h, and NiNb2O6(NN) was calcined at 1000 ℃ for 6 h. Second, IN, NN, PbO, TiO2were mixed and calcined at 800–850 ℃ for 2 h with addition of 4mol% PbO for compensating its evaporation during sintering. Third, the calcined powders were mixed with 5wt% polyvinyl alcohol as binder and then pressed into pellets. After burning out the binder at 550 ℃ for 2 h, the pellets were sintered at 1050–1150 ℃ for 2 h in a sealed Al2O3crucible to obtain the desired ceramics.

For structural analysis, the sintered samples after being pulverized into powder were examined by X-ray diffraction technique with CuKα radiation (MiniFlex II, Rigaku, Japan). A scanning electron microscope (JSM- 6700F, JEOL Tokyo, Japan) was used to investigate the morphology and microstructure of the ceramics. The die-lectric properties were analyzed using a computer- controlled Alpha-A broad band dielectric/impedance spe-ctrometer (Novocontrol, GmbH, Germany), with an AC signal of 1.0 V (peak-to-peak) applied. An aix-ACCT2000 analyzer (=4 Hz) was used to display the ferroelectric hysteresis loops at room temperature. All samples were poled at 90 ℃ for 15 min in silicone oil immersed in silicone oil using a DC electric field which was 1.5 times higher than coercive field. The piezoelectric coefficients33were measured using a quasi-static33meter (Institute of Acoustics, CAS, model ZJ-4AN, China)

2 Results and discussion

2.1 Structural analysis

The XRD patterns of 0.10PIN-(0.90–)PNN-PT (0.35, 0.37, 0.39 and 0.41), 0.30PIN-(0.70–)PNN-PT (0.33, 0.35, 0.37 and 0.39) and 0.50PIN-(0.50–)PNN-PT (0.31, 0.33, 0.35 and 0.37) are shown in Fig. 1. All samples exhibit pure perovskite phase without any secondary phase. It can be observed that the structure of the ceramics samples is transferred from rhombohedral to tetragonal phase with increasing PT content according to the XRD patterns of (200)/(002) reflections around 2=45°, identifying one peak in rho-mbohedral phase and two peaks in tetragonal phase.

The MPB was determined to be at0.37–0.39, 0.35–0.37, 0.33–0.35 for 0.10PIN, 0.30PIN and 0.50PIN series, respectively. According to the XRD results, the MPB phase diagram of PIN-PNN-PT ternary system at room temperature was delimited as shown in Fig. 2.

Fig. 1 XRD patterns and enlarged patterns of (200)/(002) reflections of PIN-PNN-PT ceramics at room temperature

(a) 0.10PIN-(0.90–)PNN-PT; (b) 0.30PIN-(0.7–)PNN-PT; (c) 0.50PIN-(0.5–)PNN-PT

SEM micrographs of fracture surface of selected 0.10PIN-(0.90–)PNN-PT ceramics are showed in Fig. 3, indicating high density and few pore. In addition, it was found that the average grain size vary slightly for samples with different contents of PNN.

2.2 Dielectric properties

The temperature dependence of dielectric constant (?) and dielectric loss (tan) of 0.50PIN-(0.50–)PNN-PT are shown in Fig. 4. It can be seen that the Curie temperatureCincreases with increasing PT content. The values ofCare improved significantly compared with PNN-PT binary systems[6]. In addition, the Curie temperatureCisindependentof frequency for 0.50PIN-(0.50–)PNN-PT, indicating normal ferroelectric behavior. The dielectric loss increased significantly when temperature above the Curie temperature, which was caused by leakage conductance loss.

Besides, as shown in Fig. 5(a), the values of tandecrease with increasing PIN level, indicating that the introduction of PIN into PNN-PT system can effectively reduce dielectric loss and conductivity, which is a shortcoming of PNN-PT. The Curie temperatureCas a function of PT contents is displayed in Fig. 5(b). The Curie temperaturesCincrease abruptly from 109 to 191 ℃ for 0.10PIN series, from 171 to 222 ℃ for 0.30PIN series and from 221 to 228 ℃ for 0.50PIN series with increasing PT, respectively. Detailed parameters of dielectric properties measured at 1 kHz are listed in Table 1.

Fig. 2 MPB region of PIN-PNN-PT ternary system at room temperature

Fig. 3 SEM micrographs of fracture surface of 0.10PIN-xPNN-yPTceramics

(a) 0.10PIN-0.49PNN-0.41PT; (b) 0.10PIN-0.51PNN-0.39PT; (c) 0.10PIN-0.53PNN-0.37PT; (d) 0.10PIN-0.55PNN-0.35PT

Fig. 4 Temperature dependence of dielectric constant (e?) and dielectric loss (tanδ) of 0.50PIN-(0.50-x)PNN-xPT ceramics

(a) 0.50PIN-0.13PNN-0.37PT; (b) 0.50PIN-0.15PNN-0.35PT; (c) 0.50PIN-0.17PNN-0.33PT; (d) 0.50PIN-0.19PNN-0.31PT

Fig. 5 (a) tanδ, (b) TC and (c) d33 as a function of PT contents for yPIN-(1–x–y)PNN-xPT ceramics.

2.3 Piezoelectric properties

Fig. 5(c) shows piezoelectric constant33as a function of PT content for the PIN-PNN-PT ternary ceramics. It is clearly observed that with increasing PT content, the piezoelectric constant33increases initially, reaching the maximum value at MPB region, and then decreases. The values of33vary from 317 to 364 pC/N for 0.10PIN series, from 375 to 417 pC/N for 0.30PIN series, from 362 to 401 pC/N for 0.50PIN series. The optimal electrical properties appear in the MPB composition of 0.30PIN-0.33PNN-0.37PT with the33417 pC/N. Detailed33of all samples were listed in Table 1.

2.4 Ferroelectric properties

The ferroelectric hysteresis loops of the PIN-PNN-PT ceramics were characterized as shown in Fig. 6, exhibiting well-saturated loops. The value of remnant polarization (r) and coercive field (c) of PIN-PNN-PT ceramics are displayed in Table 1. With increasing PT content, the remnant polarizationrwas found to increasefirstly, reaching the maximum at MPB composition, and then decrease, which is caused by the coexistence of rhombohedral and tetragonal phases at the MPB region. On the contrary, the coercive fieldcwas found to decrease at first, reaching the minimum at MPB region, and then increase with increasing of PT content, which was due to that free energy profile flatten at MPB region and then the reduced energy barrier causes the polarization easy to switch[19-21].

3 Conclusions

In conclusion, the PIN-PNN-PT ternary ceramics with compositions near MPB region were synthesized using a two-step method and characterized by X-ray diffraction,dielectric, ferroelectric and piezoelectric measurements. The MPB region of the ternary system were obtained. The optimized composition was found to be the composition of 0.30PIN-0.33PNN-0.37PT with the33417 pC/N,C200 ℃,′=3206, tan0.033,r33.5 μC/cm2andC14.1 kV/cm. The PIN-PNN-PT ternary ferroelectric ceramics had the advantage of PIN-PT and PNN-PT, shows larger piezoelectric performance, higherCand lower dielectric loss than those of PNN-PT ceramics, makes it a potential candidate utilize in transducer and actuator applications.

Table 1 The values of ε′, tanδ, d33, TC, Pr and EC of yPIN-(1–x–y)PNN-xPT ternary ceramics

0.10PIN, 0.30PIN and 0.50PIN indicate the=0.10, 0.30 and 0.50, respectively, inPIN-(1––)PNN-PT

Fig. 6 Ferroelectric hysteresis of (a) 0.10PIN-xPNN-yPT, (b) 0.30PIN-xPNN-yPT, and (c) 0.50PIN-xPNN-yPT ceramics

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三元陶瓷Pb(In1/2Nb1/2)O3-Pb(Ni1/3Nb2/3)O3-PbTiO3準(zhǔn)同型相界附近組分的介電、鐵電和壓電性能

郭霖1,2, 喬顯集2, 李修芝2, 龍西法2, 何超2

(1. 福建師范大學(xué) 化學(xué)與材料學(xué)院, 福州 350117; 2. 中國(guó)科學(xué)院 福建物質(zhì)結(jié)構(gòu)研究所, 光電材料化學(xué)與物理重點(diǎn)實(shí)驗(yàn)室, 福州 350002)

鉛基復(fù)合鈣鈦礦鐵電材料廣泛應(yīng)用于機(jī)電傳感器、致動(dòng)器和換能器。二元鐵電固溶體Pb(Ni1/3Nb2/3)O3- PbTiO3(PNN-PT)由于其在準(zhǔn)同型相界(MPB)區(qū)域具有優(yōu)異的壓電、介電性能而備受關(guān)注。然而較大的介電損耗和較低的居里溫度限制了其在高溫高功率器件方面的應(yīng)用。本研究通過(guò)引入Pb(In1/2Nb1/2)O3(PIN)作為第三組元改善PNN-PT的電學(xué)性能, 提高其居里溫度; 通過(guò)兩步法合成了MPB區(qū)域的三元鐵電陶瓷Pb(In1/2Nb1/2)O3- Pb(Ni1/3Nb2/3)O3-PbTiO3(PIN-PNN-PT), 研究了其結(jié)構(gòu)、介電、鐵電和壓電性能。制備的所有組分陶瓷具有純的鈣鈦礦結(jié)構(gòu)。隨著PT含量的增加, 陶瓷結(jié)構(gòu)從三方相轉(zhuǎn)變?yōu)樗姆较?。通過(guò)XRD分析得到了室溫下PIN-PNN-PT體系的MPB相圖。體系的居里溫度由于PIN的加入得到了很大的提高, 更重要的是PIN的引入降低了PNN-PT體系的介電損耗和電導(dǎo)。MPB處的組分展現(xiàn)出了優(yōu)異的電學(xué)性能, 室溫下, 性能最優(yōu)組分為0.30PIN-0.33PNN-0.37PT:33=417 pC/N,C=200 ℃,′= 3206, tan=0.033,r=33.5 μC/cm2,C=14.1 kV/cm。引入PNN-PT的PIN第三組元使得體系的居里溫度和壓電性得到提高的同時(shí)降低了的介電損耗和電導(dǎo)率, 因此, PIN-PNN-PT三元鐵電陶瓷在高溫高功率換能器等方面具備一定的應(yīng)用潛力。

鐵電陶瓷; 準(zhǔn)同型相界; 居里溫度; 壓電性能

TQ174

A

2020-01-20;

2020-02-20

Science and Technology Project of Fujian Province (2018H0044, 2019H0052)

GUO Lin(1995–), male, Master candidate. E-mail: guolin@fjirsm.ac.cn

郭霖(1995–), 男, 碩士研究生. E-mail: guolin@fjirsm.ac.cn

HE Chao, professor. E-mail: hechao@fjirsm.ac.cn

何超, 研究員. E-mail: hechao@fjirsm.ac.cn

1000-324X(2020)12-1380-05

10.15541/jim20200042