Multifunctional bismuth sodium titanate-based ferroelectric ceramics with bright red emission and large strain response

Journal Pre-proof Multifunctional Bismuth Sodium Titanate-based Ferroelectric Ceramics with Bright Red Emission and Large Strain Response

Cen Liang, Jigong Hao, Wei Li, Peng Fu, Juan Du, Peng Li, Wangfeng Bai, Linjiang Tang PII:

S0254-0584(20)30087-0

DOI:

https://doi.org/10.1016/j.matchemphys.2020.122706

Reference:

MAC 122706

To appear in:

Materials Chemistry and Physics

Received Date:

08 August 2019

Accepted Date:

21 January 2020

Please cite this article as: Cen Liang, Jigong Hao, Wei Li, Peng Fu, Juan Du, Peng Li, Wangfeng Bai, Linjiang Tang, Multifunctional Bismuth Sodium Titanate-based Ferroelectric Ceramics with Bright Red Emission and Large Strain Response, Materials Chemistry and Physics (2020), https://doi.org/10.1016/j.matchemphys.2020.122706

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Journal Pre-proof

Multifunctional Bismuth Sodium Titanate-based Ferroelectric Ceramics with Bright Red Emission and Large Strain Response Cen Liang1, Jigong Hao1,*, Wei Li1,*, Peng Fu1, Juan Du1, Peng Li1, Wangfeng Bai2, Linjiang Tang3 1College

of Materials Science and Engineering, Liaocheng University, Liaocheng 252059, People’s Republic of China

2College

of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou, 310018, China 3Beijing

Spacecrafts, Beijing 100094, China

ABSTRACT In this paper, we systematically studied the structure and properties of SrPrAlO4-modified (Bi0.5Na0.5)0.935Ba0.065TiO3 (BNT-0.065BT) lead-free piezoelectric ceramics. There is no impurity in the SrPrAlO4-modified BNT-0.065BT, and all samples form pure perovskite structure. The substitution of SrPrAlO4 induces the transformation of ferroelectric to ergodic relaxor phase. As a result, a large electric-field induced strain of 0.35% (@70kV/cm, corresponds to a large signal piezoelectric d33* (Smax/Emax) of 500 pm/V) is obtained when the SrPrAlO4 dopant concentration is 0.012. In addition, the large strain in this material is very resistant to field cycling, rendering the material attractive for its fatigue-free behavior. Moreover, SrPrAlO4-modified

ceramics

exhibit

orange-red

emission

under

450

nm

photoexcitation. There is a strong red emission peak at 610 nm corresponded to the transition of 1D2 →3H4 and a weak red emission peak at 660 nm ascribed to the 3P0 _____________________________________________ * Corresponding authors. Email address: [email protected]; [email protected]

Journal Pre-proof →3F2 transition. The multifunctional characteristics with good electrical and luminescent properties in BNT-0.065BT-xSrPrAlO4 ceramics render the materials may have broad application prospects in new devices with multiple functions. Keyword: Lead-free ceramics, Phase structure, Filed-induced strain, Fatigue resistant, Photoluminescence 1.

Introduction Lead zirconate titanate (PZT) ceramics act an important role in technological

applications [1]. However, PZT contains much lead that is toxicity and harmful to the environment. As a result, people are questing for lead-free ceramics to replace PZT. A number of researches have been reported and various kinds of lead-free piezoceramics have been fabricated [2-4]. Among them, (Bi0.5Na0.5)TiO3-BaTiO3 (BNT-BT)-based binary system presents a giant electric field-induced strain [5-7], which makes BNT-BT has significant potential in actuator applications [6, 8-10]. The beginnings of scientific interest in high-strain BNT-based ceramics can be dated back to the year of 2007 when Zhang et al [10] achieved the high strain value of 0.45% in BNT-BT-(K, Na)NbO3 ceramics which is comparable to the strain response to PZT ceramics. In recent years, people no longer only focus on the single electrical performance of piezoelectric ceramics, but also search for multifunctional piezoelectric ceramics. One way is doping rare earth (RE) ions into ferroelectrics [7, 8, 11-15]. For BNT-BT materials, REs doping can not only render ferroelectrics have luminescent properties, but improve the strain performance due to its “destructive effect” of the long-term ferroelectric order [16]. Generally, improved strain performance of BNT-BT-based 2

Journal Pre-proof ceramics is achieved by the addition of ABO3 [17-19], AB2O4 [20] compounds and metal dopants [21]. When these additives contain RE ions, modified ceramics show good luminescent properties besides the inherent large strain response. SrPrAlO4 is a perovskite-like structure composed of ABO3 perovskite and AB salt layer [22, 23]. The ion radius of Sr2+, Pr3+ in SrPrAlO4 is 1.31 Ǻ and 1.126 Ǻ, respectively, which will easily enter into A site of BNT-BT lattice. The ion radius of Al3+ in SrPrAlO4 is 0.535 Ǻ, which will easily enter into B site of BNT-BT lattice [11]. When SrPrAlO4 is used as an additive to BNT-BT ceramics, it is expected that SrPrAlO4 and BNT-BT can form a solid solution. An enhancement of field-induced strain is expected in SrPrAlO4-modified ceramics due to the lattice distortion induced by doping. Moreover, SrPrAlO4 also contains a rare earth element Pr, so it is expected that the luminescent properties will be excited to realize electric-luminescent integration

of

BNT-BT-based

materials.

(1-x)(Bi0.5Na0.5)0.935Ba0.065TiO3-xSrPrAlO4

In

this

study,

(BNT-0.065BT-xSrPrAlO4)

lead-free

ceramics were prepared, and the phase structure, electrical properties and luminescent properties of ceramics were mainly studied. 2.

Experimental BNT-0.065BT-xSrPrAlO4 (x=0.000-0.015) lead-free ceramics were prepared by

solid state reaction using Na2CO3 (99.8%), BaCO3 (99%), SrCO3 (99%), Al2O3 (99.99%), Pr6O11 (99.9%) from Sinopharm Chemical Reagent, Bi2O3 (99.975%) and TiO2 (99.6%) from Alfa Aesar as raw materials. The weighted raw materials were milled in ethanol for 15 hours. After drying, the powders were calcined at 850oC for 4 3

Journal Pre-proof hours. Then, the calcined powder is grinded again in ethanol for 15 hours again. After mixed with the Polyvinyl Alcohol (PVA), the powders were pressed into circular discs under certain pressure. Finally, the green bodies were sintered at 1130 oC for 2 hours. X-ray diffraction (XRD, Bruker D8 Advance, Germany) and Raman scattering measurements (LabRAM HR800, air-cooled CCD array detector, Horiba Jobin-Yvon, France) was adopted to analyze the crystal structure of the ceramics. Electrical field related parameter including polarization hysteresis (P-E), bipolar strain (S-E) and unipolar strain (S-E) were measured by ferroelectric analyzer (aix-ACCT Inc, Germany). For the piezoelectric properties, the samples were poled in silicon oil at room temperature under 50 kV/cm for 20 min, and piezoelectric measurements were then carried out using a quasi-static d33-meter YE2730 (SINOCERA, China). The photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopy were recorded by spectrofluorometer (FLS920, Edinburgh Instruments, UK). 3.

Result and discussion Fig. 1 shows the XRD spectra of the BNT-0.065BT-xSrPrAlO4 ceramics with

different SrPrAlO4 contents. Sharp diffraction peaks are observed in the studied system, which is considered to be a typical pure perovskite structure with high crystalline quality. The result implies that SrPrAlO4 has formed a solid solution with BNT-0.065BT ceramics. As we have known, BNT-BT ceramic consists of rhombohedral BNT and tetragonal BT [17]. When BT content is 6.5mol%, the formed BNT-0.065BT has a rhombohedral-tetragonal ferroelectric phase coexistence 4

Journal Pre-proof structure, which is characterized by (002) and (200) peak splitting, and the strength ratio I(200)/I(002) of 2:1 [24]. In the present work, pure BNT-0.065BT sample obviously shows

splitting

of

the

(200)

reflection,

confirming

the

sample

has

rhombohedral-tetragonal coexisted phases [25]. As the content of SrPrAlO4 increases, peak splitting of (200) near 2θ = 46o becomes progressively less obvious. This result indicates that the phase structure of the materials gradually changes from rhombohedral-tetragonal ferroelectric phase to a psedocubic symmetry with the increase of SrPrAlO4 content. Compared to XRD analysis, Raman spectroscopy can reflect structural information of a sample from a smaller size scale (< 10 nm). Therefore, in order to further study the phase structure of the materials, we performed Raman spectroscopy analysis on the BNT-0.065BT-xSrPrAlO4 system, as shown in Fig. 2. Similar to other BNT-based ceramics, it is easy to detect three main regions in the Raman spectrum [19], that is, the Ti-O band vibration mode near the wave number of 278 cm-1, the vibration of the corresponding TiO6 octahedron in the wave number range 450-700 cm-1, and vibration superposition of "longitudinal modes" A1 and E above 700cm-1. It can be observed that the BNT-0.065BT material has obvious two scattering peaks under Ti-O bond vibration mode, which proves that the material has the coexistence of rhombohedral and tetragonal phases [19]. With the increasing SrPrAlO4 content, the two bands corresponding to Ti-O vibration get close to each other, and the peak height difference of the two bands become smaller, as indicated by the dotted line in this figure. So we think that if the SrPrAlO4 content is high enough, the two bands 5

Journal Pre-proof corresponding to Ti-O vibration would merge into a single band. In addition, we found that the relative intensity of the TiO6 octahedron vibration mode in the range of 450–700 cm-1 is gradually weakened with the increase of SrPrAlO4 content. In this sense, we can conclude that SrPrAlO4-doping enhanced the symmetry of the crystal structure of the BNT-0.065BT material. Compared with the XRD results, SrPrAlO4-modied materials at high doping level favor a psedocubic symmetry. Fig. 3 shows the scanning electron microscopy (SEM) images of BNT-0.065BT-xSrPrAlO4 ceramics. All samples appear in a relatively dense microstructure without abnormal grains. The results indicate that ceramics have been well sintered. The grain size distribution is studied by the “nanometer” software, as shown in Fig. 4. The average grain size of the BNT-0.065BT-xSrPrAlO4 samples is 0.70 m, 0.61 m, 0.56 m, 0.58 m, 0.62 m and 0.52 m, for x = 0, 0.003, 0.006, 0.009, 0.012, 0.015, respectively. The decreased average grain size implies that SrPrAlO4 in BNT-0.065BT material acts as a grain growth inhibitor. Fig. 5 (a) shows the P-E curves (inset is I-E curves) of BNT-0.065BT-xSrPrAlO4 with x = 00.015. The remnant polarization Pr and coercive field Ec of the ceramics are summarized in Fig. 5 (b). Obviously, pure BNT-0.065BT with saturated hysteresis loop shows a typical ferroelectric nature. In the I-E curve, a sharp peak of polarization current (marked P1) is observed near Ec in pure BNT-0.065BT. With the increase of SrPrAlO4 content, decreased Pr and Ec is noted, which suggests that the ferroelectric order of BNT-0.065BT is destroyed by SrPrAlO4 dopant [26]. In composition with x = 0.006, a contracted polarization hysteresis loop along with two current peaks 6

Journal Pre-proof (recorded as P1 and P2) is observed, and these results show that the ferroelectric order of unmodified BNT-0.065BT was destroyed by the addition of SrPrAlO4. Pinched P-E loops in composition with x = 0.006 indicates the “non-polar” phase (ergodic relaxor) at zero electric field. Under an applied electric field, it can convert to a ferroelectric phase [19]. Such a transition produced a large stain response [8], as showed in Fig. 6. Fig. 6 (a) shows the bipolar strain curve of BNT-0.065BT-xSrPrAlO4 ceramics recorded at 10 Hz and room temperature. For samples with x = 0.000 and 0.003, the bipolar strain curves show butterfly shaped curves with an obvious negative strain Sneg (which can be also be seen from Fig. 6 (b)), confirming the typical ferroelectric nature in both materials [27]. When x reaches up to 0.006, the butterfly-shaped strain curve changes into the horn-shaped one, meanwhile, the negative strain Sneg of ceramics almost disappears and the positive strain Spos value increases drastically. The increase in the content of SrPrAlO4 induces a transition from ferroelectric to ergodic relaxor in BNT-0.065BT-xSrPrAlO4 ceramic materials. According to the XRD data, with the increasing content of SrPrAlO4, the ceramics have a psedocubic phase, which may lead to the destruction of ferroelectric order and reduced of polarization degree. So the large strain behavior is caused by the destruction of ferroelectric order induced by SrPrAlO4 doping in the studied system [17]. Fig. 6 (b) depicts the change of negative strain Sneg and positive strain Spos with composition in BNT-0.065BT-xSrPrAlO4 system. From Fig. 6 (b) we can see that Sneg almost disappears at x = 0.006. Meanwhile, a drastic increase of Spos is observed, indicating that the ergodic 7

Journal Pre-proof relaxation phase starts to emerge. Fig. 7 (a) shows the strain response of BNT-0.065BT-xSrPrAlO4 under unipolar electric field cycling. When x = 0.012, a large strain response of 0.35% (70kV/cm) with significant hysteresis behavior (nonlinear response) is observed. For samples with x = 0 and 0.003, however, the unipolar strain value increases linearly with increasing electric field, showing a linear strain response. In general, the nonlinear strain response with large hysteresis is caused by external effect align with domain movement [28]. For ferroelectric materials, however, the linear strain response is primarily due to the inherent contribution of the piezoelectric effect [29, 30]. The intrinsic mechanism behind the large strain response can be further analyzed by comparing the piezoelectric and strain response. Fig. 7 (b) and (c) plots the small-signal d33 and large-signal d33* (Smax/Emax) of BNT-0.065BT-xSrPrAlO4, respectively. It can be seen from the Fig. 7 (b) and (c) that the d33 decrease with increasing SrPrAlO4 content, whereas d33* increases with increasing SrPrAlO4 content. At x = 0.012, d33* reaches up to 500 pm/V, while the d33 reduces down to 27 pC/N. This proves that the nonlinear strain response of the sample in this system mainly comes from the contribution of the external domain wall movement and rarely from contribution of the inherent contribution of the piezoelectric effect. Meanwhile, it further confirms that the generation of high electro-strain of BNT-based material is based on the sacrifice of the piezoelectric property of the material. The weak piezoelectric property of 0.012SrPrAlO4 sample also confirms the appearance of ergodic relaxation phase in the sample [18, 19]. 8

Journal Pre-proof Fig. 8 shows the temperature dependence of the dielectric constant (εr) and dielectric loss (tanδ) of unpoled BNT-0.065BT-xSrPrAlO4 ceramics. From the results of Fig. 8, some changes are observed in the dielectric properties after modified with SrPrAlO4. For samples of x = 0.000, 0.003, 0.006, 0.009, 0.012, and 0.015, there is a dielectric constant peak at about 233 oC, 226 oC, 220 oC, 207 oC, 211 oC, and 202 oC, respectively. The dielectric peak moves toward low temperature as a whole. Near the temperature of Tm, BNT-0.065BT-xSrPrAlO4 exhibits a broad dielectric peak, which may be due to relaxation caused by a square polar nanoparticles (PNRs) present in rhombohedral PNRs [31, 32]. According to previous reports [19, 31], there generally exists a dielectric peak at a low temperature. However, no dielectric peak at low temperature is found in these samples, this may be related to the “unpoled state” of the samples. Poling treatment generally induces such a low temperature dielectric anomaly [32]. Recently, the depolarization current of the thermoelectric measurement was used for Td discrimination of poled samples. Fig. 9 shows the temperature dependence of thermally stimulated depolarization currents (TSDC), where Td is determined by the peak value of the depolarization current. The experimental results show that when SrPrAlO4 was added into pure BNT-0.065BT, Td moves to the low-temperature direction, indicating that the ferroelectric-relaxor phase transition is caused by compositional changes [33]. In addition, pyroelectricity value of the SrPrAlO4 ceramics decreases, indicating that SrPrAlO4 has a significant inhibitory effect on pyroelectricity value of the ceramic. The d33 of the material was investigated by 9

Journal Pre-proof annealing method with the annealing temperature. The poled sample was placed in annealing furnace at different temperatures for 20 min. After taking out, d33 was measured at room temperature. Then, the d33 at room temperature after each annealing temperature treatment is plotted with the annealing temperature, as showed in Fig. 9. For BNT-0.065BT-xSrPrAlO4, the depolarization behavior occurs near the Td, and the performance of d33 decreases sharply around Td. Fig. 10 shows the complex impedance spectra of BNT-0.065BT-xSrPrAlO4 ceramics in the 500-700 oC frequency range from 0.01 Hz to 20 MHz. Obviously, it can be seen that as the temperature increases, the impedance value gradually decreases, indicating that BNT-0.065BT-xSrPrAlO4 is a kind of negative temperature coefficient materials. In addition, impedance maps of ceramics doped with different SrPrAlO4 content show only one semicircle and from the illustration the horizontal intercepts are basically zero. This result indicates that the impedance is controlled by a single local relaxation mechanism in the measured temperature range [34]. The activation energy (Ea) of the BNT-0.065BT-xSrPrAlO4 can be detected by the Arrhenius equation: σ = σ0 exp (-Ea/kT), where σ0 is the pre-exponential factor, Ea is the activation energy, k is Boltzmann constant, and T is the absolute temperature. The dielectric relaxation in perovskite materials is related to oxygen vacancies [35]. The activation of oxygen vacancies varies from 0.5 eV to 2 eV, depending on the concentration of oxygen vacancies [36, 37]. The Ea of BNT-0.065BT-xSrPrAlO4 is in the range of 1.10-1.23 eV as shown in Fig. 11, therefore, the Ea of BNT-0.065BT-xSrPrAlO4 is closely to oxygen vacancies migration and the oxygen 10

Journal Pre-proof void dominates the conductivity of BNT-0.065BT-xSrPrAlO4 in the test temperature range [38]. Fig. 12 shows the (a) P–E loops, (b) bipolar S–E curves and (c) unipolar S–E curves of BNT-0.065BT-0.012SrPrAlO4 ceramics at different temperature (25– 120°C). The variations of strain and remanent polarization Pr with temperature were presented in Fig. 12 (d). From Fig. 12(a), as the temperature increases, the shape of the hysteresis loop of BNT-0.065BT-0.012SrPrAlO4 does not change significantly, and it can maintain the pinched hysteresis loop with the slight decrease of Pr with increasing temperature (from Fig. 12 (d)). The change of bipolar strain and unipolar strain

at

different

temperatures

indicates

that

the

strain

of

BNT-0.065BT-0.012SrPrAlO4 decreases with increasing temperature. According to the strain value curve of Fig. 12 (d), the strain value is reduced from 0.32% to 0.25%. As a whole, the studied sample exhibits relatively good temperature stability, as droop rate of strain is only 0.07%. Suitable materials for industrial applications also have to be reliable under long-term electric cycling. Therefore, the fatigue characteristics are very important for industrial operation [39]. Fig. 13-15 shows the fatigue behavior of the BNT-0.065BT-0.012SrPrAlO4 ceramic in the cycles of 105. Fig. 13 shows the polarization hysteresis loops of BNT-0.065BT-0.012SrPrAlO4 under different fatigue cycles. It is found that the ceramic still exhibits obvious pinched hysteresis loop behavior after 105 switching cycles. During field cycling, the remanent polarization Pr intensity

fluctuation

is

small.

Fig.

14

shows

the

bipolar

strain

of

BNT-0.065BT-0.012SrPrAlO4 ceramic for 105 cycles. It can also be seen that the 11

Journal Pre-proof ceramic still maintain a high strain level after 105 filed cycling. Fig. 15 shows the P–E loops and bipolar/unipolar S–E curves of BNT-0.065BT-0.012SrPrAlO4 ceramics before and after 105 fatigue cycles. The electric field-induced reversible relaxation phase and the ferroelectric phase are the reason for good fatigue resistance of BNT-0.065BT-0.012SrPrAlO4 [8]. This discovery provides current opportunities for applications as nonlinear actuators that require improved cycle reliability. Fig. 16 (a) shows the photoluminescence excitation (PLE) (λem = 610 nm) and photoluminescence (PL) (λex = 450 nm) spectra of BNT-0.065BT-0.003SrPrAlO4 at room temperature. When the emission wavelength is fixed at 610 nm, three distinct excitation spectra are observed, which are located at approximately 440 nm, 475 nm and 490 nm, respectively. The three excitation peak are 3H4 to 3PJ (J=0, 1, 2) typical 4f-4f transition [40-42], the peak at 450 nm corresponds to the 3H4 → 3P2 transition, the peak at 475 nm corresponds to the 3H4 → 3P1 transition, and the peak near 490 nm corresponds to the 3H4 → 3P0 transition. There is a peak near 610 nm, and there is a peak near 660 nm. The strong red emission peak is caused by 1D2 → 3H4 transition, and the peak of 660 nm is due to the transition from 3P0 to 3F2. More intuitive level transition can be obtained from Fig. 16 (b). Fig. 17 is a PL spectroscopic observation of BNT-0.065BT-xSrPrAlO4 ceramics with different dopants, it can be seen that all materials have no unnecessary emission peaks. The results show that the intensity of the emission peaks with the different doping amount is also different, and the intensity of the emission peaks is decreasing. When the doping amount is greater than 0.003, the deceased PL intensity may be caused by the concentration quenching effect, that 12

Journal Pre-proof is, the non-radiative transition from Pr3+ ions to Pr3+ ions occurs. The inset is a color coordinate (CIE) plot of different doping amounts. It can be seen from the figure that basically all the color coordinate points are in one place, x is about 0.65, y is about 0.34, and the colors are all bright orange. 4.

Conclusion The effect of SrPrAlO4 doping on the electro-optical properties of

BNT-0.065BT-xSrPrAlO4 ceramics is investigated in this work. SrPrAlO4 induced a phase transformation from a typical ferroelectric phase to a relaxor phase. Due to the emerge of relaxor phase, the unipolar strain value was improved upto 0.35% (@70kV/cm, equivalently a large signal d33* of 500 pm/V) when the doping amount of SrPrAlO4 is 0.012. In addition to large strain response, BNT-0.065BT-xSrPrAlO4 ceramics also exhibit strong orange-red emission under photoexcitation. The SrPrAlO4-doped ceramics exhibit two emission peaks at an excitation wavelength of 450 nm, the 1D2 → 3H4 transition is at 610 nm and the emission peak at 660 nm is a 3P

0

→ 3F2 transition. The results show that BNBT6.5-xSrPrAlO4 ceramics have broad

application prospects in new multi-functional devices because of its good luminescent and electrical properties. Acknowledgements This work was supported by the National Key R&D Program of China (No. 2016YFB0402701), Innovation Team of Higher Educational Science and Technology Program in Shandong Province (No. 2019KJA025), Natural Science Foundation of Shandong Province of China (Nos. ZR2018MEM011 and ZR201709270099), Project 13

Journal Pre-proof of Shandong Province Higher Educational Science and Technology Program (No. J17KA005), Opening Project of Key Laboratory of Inorganic Functional Materials and Devices, Chinese Academy of Sciences (Grant No. KLIFMD201705), Research Foundation of Liaocheng University (No.318011906). References [1] G. H. Haertling, Ferroelectric ceramics: history and technology, J. Am. Ceram. Soc. 82(4) (1999) 797-818. [2] Y. Qiu, X. Chen, H. Lian, J Ma, W. Ouyang, Structure and electrical behavior of unpoled and poled 0.97(Bi0.5Na0.5)0.94Ba0.06TiO3-0.03BiAlO3 ceramics. Mater. Chem. Phys. 202 (2017) 197-203. [3] A. Hussain, J.U. Rahman, F. Ahmed, J.S. Kim, M.H. Kim, T.K. Song, W.J. Kim, Plate-like Na0.5Bi0.5TiO3 particles synthesized by topochemical microcrystal conversion method, J. Eur. Ceram. Soc. 35 (3) (2015) 919-925. [4] J. Rödel, W. Jo, K.T.P. Seifert, E.-M. Anton, T. Granzow, D. Damjanovic, Perspective on the Development of Lead-free Piezoceramics, J. Am. Ceram. Soc. 92 (6) (2009) 1153-1177. [5] T. Takenaka. Current developments and future prospects of lead-free piezoelectric ceramics, Materials Integration, J. Eur. Ceram. Soc. 25 (2005) 2693-2700. [6] J. Hao, W. Li, J. Zhai, H. Chen, Progress in high-strain perovskite piezoelectric ceramics, Mater. Sci. Eng. R. 135 (2019) 1-57. [7] Yao, F. Wang, F. Xu, C.M. Leung, T. Wang, Y. Tang, W. Shi, Electric field induced giant strain and photoluminescence enhancement effect in rare earth modified lead-free piezoelectric ceramics, Acs Appl. Mater. Inter. 7 (2015) 5066-5075. [8] H.L. Pan, J.J. Zhang, X.R. Jia, H.J. Xing, J.Y. He, J.Y. Wang, F. Wen, Large electrostrictive effect and high optical temperature sensitivity in Bi0.5Na0.5TiO3-BaTiO3-(Sr0.7Bi0.18Er0.02)TiO3 luminescent ferroelectrics. Ceram. Inter. 44 (2018) 5785–5789. [9] W. Jo, R. Dittmer, M. Acosta, J. Zang, C. Groh, E. Sapper, K. Wang, J. Rödel, Giant electric-field-induced strains in lead-free ceramics for actuator applications-status and perspective, 14

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96-104. [22] B. Liu, L. Yi, X.Q. Liu, X.M. Chen, Structure and microwave dielectric properties of SrSmAlO4-Sr2TiO4 solid solutions, J. Electroceram. 34 (2-3) (2014) 114-121. [23] J. Hao, Z. Xu, R. Chu, W. Li, P. Fu, J. Du, G. Li, Fatigue-resistant, temperature-insensitive strain behavior and strong red photoluminescence in Pr-modified 0.92(Bi0.5Na0.5)TiO3–0.08 (Ba0.90Ca0.10)(Ti0.92Sn0.08)O3 lead-free ceramics, J. Eur. Ceram. Soc. 37 (2) (2017) 877-882. [24] J. Hao, Z. Xu, R. Chu, W. Li, P. Fu, J. Du, G. Li, Structure evolution and electrostrictive properties in (Bi0.5Na0.5)0.94Ba0.06TiO3–M2O5 (M=Nb, Ta, Sb) lead-free piezoceramics, J. Eur. Ceram. Soc. 36 (16) (2016) 4003-4014. [25]

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Journal Pre-proof Figure captions Fig. 1. XRD patterns of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4contents. Fig. 2. Raman scattering spectra of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4 contents. Fig. 3. The surface morphology of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4 contents. Fig. 4. The particle size distribution of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4 contents. Fig. 5. (a) The P-E hysteresis loops of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4 contents. (b) The Pr and Ec values for BNT-0.065BT-xSrPrAlO4 samples with different SrPrAlO4 contents. Fig. 6. (a) The bipolar strain curves of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4 contents. (b) The summary of negative strain Sneg and positive strain Spos of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4 contents. Fig. 7. (a) The unipolar strain curves of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4 contents. (b) The small-static d33 and (c) The large signal d33* of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4 contents. Fig. 8. The dielectric constant (εr) and dielectric loss (tanδ) versus the temperature of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4 contents at 1 MHz. Fig. 9. Thermal current and d33 change with temperature of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4 contents. Fig. 10. The impedance spectra of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4 19

Journal Pre-proof contents in the frequency range of 0.01 Hz to 20 MHz over 500–700 °C. Fig. 11. Arrhenius plots of σdc conductivity of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4 contents. Fig. 12. (a) The P–E hysteresis loops , (b) curves,

(d)

the

strain

and

bipolar S–E curves， (c) unipolar S–E

residual

polarization

strength

Pr

of

BNBT6.5-0.012SrSmAlO4 ceramics at different temperatures (25–120 °C). Fig. 13. The P–E hysteresis loops fatigue behavior of BNBT6.5-0.012SrSmAlO4 ceramics measured at 10 Hz for 105 cycles. Fig. 14. The bipolar S–E curves fatigue behavior of BNBT6.5-0.012SrSmAlO4 ceramics measured at 10 Hz for 105 cycles. Fig. 15. (a)The P–E hysteresis loops , (b)

bipolar S–E curves and (c) unipolar S–E

curves of BNBT6.5-0.012SrSmAlO4 ceramics at before fatigue and after 105 fatigue cycles. Fig. 16. (a) Room temperature PL (λex=450 nm) and PLE (λem=610 nm) spectra of BNBT6.5- 0.003SrPrAlO4 ceramics. (b) The energy level diagram of Pr3+ ions. Fig. 17. The PL spectra intensity dependence of SrPrAlO4 concentrations excited at 450 nm, and the calculated CIE chromaticity coordinates of BNBT6.5-xSrPrAlO4 with different SrPrAlO4 contents.

20

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Declaration of interests  The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:

Journal Pre-proof Journal：Materials chemistry and Physics Title: Multifunctional Bismuth Sodium Titanate-based Ferroelectric Ceramics with Bright Red Emission and Large Strain Response Article Type: Full Length Article Keywords: Lead-free ceramics, Phase structure, Filed-induced strain, Fatigue resistant, Photoluminescence Corresponding Author: Jigong Hao, ph.D; Wei Li, Ph.D Corresponding Author's Institution: Liaocheng University Corresponding Author's Email address: [email protected]; [email protected] First Author: Cen Liang Order of Authors: Cen Liang, Jigong Hao*, Wei Li*, Peng Fu, Juan Du, Peng Li, Wangfeng Bai, Linjiang Tang

Journal Pre-proof Figure 1

Fig. 1. XRD patterns of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4 contents.

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Fig. 2. Raman scattering spectra of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4 contents.

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Fig. 3. Surface morphology of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4 contents.

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Figure 4

Fig. 4. Particle size distribution of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4 contents.

Journal Pre-proof Figure 5

Fig. 5. (a) P-E hysteresis loops of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4 contents. (b) Pr and EC values for BNT-0.065BT-xSrPrAlO4 samples with different SrPrAlO4 contents.

Journal Pre-proof Figure 6

Fig. 6. (a) Bipolar strain curves of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4 contents. (b) Summary of negative strain Sneg and positive strain Spos of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4 contents.

Journal Pre-proof Figure 7

Fig. 7. (a) Unipolar strain curves of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4 contents. (b) Small-static d33 and (c) large signal d33* of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4 contents.

Journal Pre-proof Figure 8

Fig. 8. The dielectric constant (εr) and dielectric loss (tanδ) versus the temperature of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4 contents at 1 MHz

Journal Pre-proof Figure 9

Fig. 9. Thermal current and d33 change with temperature of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4 contents.

Journal Pre-proof Figure 10

Fig. 10. The impedance spectra of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4 contents in the frequency range of 0.01 Hz to 20 MHz over 500–700 °C.

Journal Pre-proof Figure 11

Fig. 11. Arrhenius plots of σdc conductivity of BNT-0.065BT-xSrPrAlO4 with different SrPrAlO4 contents.

Journal Pre-proof Figure 12

Fig. 12. (a) The P–E hysteresis loops , (b) bipolar S–E curves， (c) unipolar S–E curves， (d) the strain and residual polarization strength Pr of BNBT6.5-0.012SrSmAlO4 ceramics at different temperatures (25–120 °C).

Journal Pre-proof Figure 13

Fig. 13. The P–E hysteresis loops fatigue behavior of BNBT6.5-0.012SrSmAlO4 ceramics measured at 10 Hz for 105 cycles.

Journal Pre-proof Figure 14

Fig. 14. The bipolar S–E curves fatigue behavior of BNBT6.5-0.012SrSmAlO4 ceramics measured at 10 Hz for 105 cycles.

Journal Pre-proof Figure 15

Fig. 15. (a)The P–E hysteresis loops , (b) bipolar S–E curves and (c) unipolar S–E curves of BNBT6.5-0.012SrSmAlO4 ceramics at before fatigue and after 105 fatigue cycles.

Journal Pre-proof Figure 16

Fig. 16. (a) Room temperature PL (λex=450 nm) and PLE (λem=610 nm) spectra of BNBT6.5- 0.003SrPrAlO4 ceramics. (b) The energy level diagram of Pr3+ ions.

Journal Pre-proof Figure 17

Fig. 17. The PL spectra intensity dependence of SrPrAlO4 concentrations excited at 450 nm, and the calculated CIE chromaticity coordinates of BNBT6.5-xSrPrAlO4 with different SrPrAlO4 contents.

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Highlights: 

Ferroelectric relaxor behavior is obtained in the materials.



Large strain of 0.35% is obtained in the materials.



The materials exhibit excellent reliability characteristics.



A bright photoluminescence with a strong red-orange emission was observed.