Structural integrity and ferroelectric–piezoelectric properties of PbTiO3 coating prepared via supersonic plasma spraying

Accepted Manuscript Structural integrity and ferroelectric-piezoelectric properties of PbTiO3 coating prepared via supersonic plasma spraying Xing Zhiguo, Wang Haidou, Xu Binshi, Ma Guozheng, Huang Yanfei, Kang Jiajie, Zhu Lina PII: DOI: Reference:

S0261-3069(14)00352-5 http://dx.doi.org/10.1016/j.matdes.2014.04.077 JMAD 6468

To appear in:

Materials and Design

Received Date: Accepted Date:

27 December 2013 28 April 2014

Please cite this article as: Zhiguo, X., Haidou, W., Binshi, X., Guozheng, M., Yanfei, H., Jiajie, K., Lina, Z., Structural integrity and ferroelectric-piezoelectric properties of PbTiO3 coating prepared via supersonic plasma spraying, Materials and Design (2014), doi: http://dx.doi.org/10.1016/j.matdes.2014.04.077

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Structural integrity and ferroelectric-piezoelectric properties of PbTiO3 coating prepared via supersonic plasma spraying Xing Zhiguo1, 2, Wang Haidou1*, Xu Binshi1, Ma Guozheng1, Huang Yanfei1 Kang Jiajie3, Zhu Lina

3

1. Science and Technology on Remanufacturing Laboratory, Academy of Armored Forces Engineering, Beijing 100072, China 2. The State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China 3. School of Engineering and Technology, China University of Geosciences, Beijing 100083, China Corresponding author. Tel: +86 1066718475; Fax: +86 1066717144. E-mail address: [email protected] (H.Wang) Abstract: In order to prepare the PbTiO3 coating with high density and excellent piezoelectric properties on all kinds shape surface, the PbTiO3 coating was prepared by supersonic plasma spraying. The microstructure and mechanical properties were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectrograph (XPS). The dielectric constant and dissipation constant of the PbTiO3 coating were tested. The results show that the coating has a single ferroelectric phase with perovskite structure, and its surface is smooth and dense. In the course of spraying, about 50% PbTiO3 is decomposed into PbO and TiO2 at high temperature. The ferroelectric hysteresis is weak and the ferroelectric hysteresis loop is not completely closed, which indicates that the defects, such as ϭ 



pores and cracks, exist in the coating. Although the defects are inevitable, the PbTiO3 coating with ferroelectric and piezoelectric properties is successfully prepared. Keywords: PbTiO3 coating; plasma spraying; microstructure; piezoelectric properties; ferroelectric properties 1. Introduction PbTiO3 is a kind of perovskite structure material and has extensively been used in ferroelectric, piezoelectric and microelectronic fields[1]. The fine texture of PbTiO3 notably impacts its piezoelectric properties, and makes it possess larger tetragonal deformation [2]. It can be polarized in high pressure electric field. The polarized PbTiO3 possesses bigger aeolotropism, lower mechanical quality factor and dielectric constant [3]. It undergoes a single first order transition from cubic paraelectric phase to tetragonal ferroelectric phase at Curie temperature 494ഒ, and makes the dipole matrix and spontaneous polarization appear on the crystallographic axes. Sintering is a primary technology to produce the ceramics. Up to now, many sintering techniques, such as solid state sintering, liquid phase sintering and pressure assisted sintering, have widely been used to prepare PbTiO3 ceramics and PbTiO3 -based ceramics [4-7].PbTiO3 is a kind of ceramic which consists of volatile PbO and TiO2, when it is sintered. Compared to the PbTiO3 ceramics, PbO is volatile at high temperature, which affects the electrical properties and stochiometry of the PbTiO3. While, the ferroelectric properties are very sensitive to the composition and perovskite structure, which makes it impossible to maintain in such a long time under high temperature. The properties of PbTiO3 ceramics prepared via all kinds of sintering Ϯ 



technologies are not stable, which can’t meet the necessity of industry application. In addition, PbTiO3 films have the same basic physical properties as PbTiO3 bulk materials, which have been prepared by various chemical and physical methods, such as rf magnetron sputtering [8], pulsed laser ablation [9-12], sol-gel method [13], spin-coating [14], chemical solution deposition [15-17], hybrid chemical method [18], and etc. Y. Ye prepared the PbTiO3 films with the thickness of 20 nm via reactive magnetron sputtering, and studied the domain switching phenomena and retention properties using piezoresponse force microscopy. The results showed that the multistep deposited PbTiO3 thin films had smaller rms roughness (2.5-3.5 nm) and coercive voltage (1.68- 2.32 V), higher d33 value than single-step deposited PbTiO3 thin films[19]. However, the piezoelectric ceramics can not be used in special shapes, while the thin films can be used in all shapes, but it must be bound with the basal bodies which make it subject to severe risks easily. Thus, both of them can not be applied in complex shapes. Compared with the ceramic and the films, the coating prepared by plasma spraying possesses a series of merits. The coating can be sprayed on all kinds of parts surface, and its thickness can be controlled in the preparation process. However, the weakness of the coating is unavoidable, such as high porosity, new impurity, dissipation of composition, and etc. Among of them, the porosity is the biggest weakness of the coating, which seriously affects its performance. The porosity of the coating prepared by plasma spraying is more than 3%, and the coating with high porosity can not bear the stress in the active time [20]. ϯ 



Whereas, the coating prepared by supersonic plasma spraying not only possesses all the merits of the coating prepared by plasma spraying, but also has lower porosity, which is less than 2%. Moreover, the porosity of supersonic plasma spraying coating can be reduced by adjusting the process parameters. Thus, in this paper the microstructure of the PbTiO3 coating prepared by supersonic plasma spraying was evaluated and the piezoelectric performance related with the electrical discharge was investigated. 2. Experiments details 2.1. Preparation of the material and specimens The PbTiO3 coating was sprayed by supersonic plasma spraying equipment (HEPJet), which was manufactured by Science and Technology on Remanufacturing Laboratory. The equipment possesses more merits than common spray equipments, and has higher velocity of flame flow, particle flying speed, arc voltage, and etc. The spraying gun is the most important element of the equipment and its schematic diagram is shown in Fig. 1. The supersonic spraying gun can compress the plasma flame flow, and make the arc voltage up to 250ᨺ400 V, the flame speed above 360 m/s, and the particle flying speed up to 450 m/s. In the spraying course, the powders keep fusing in the long plasma flame flow, and are deposited on the substrate with high speed at a high temperature in a very short time, then quickly spread out and cooled down. In this research, the PbTiO3 original powders were treated by atomizing, which could enhance the density and decrease the pores of the coating. The size of the feed ϰ 



powders is 30~60 μm, and the average size is 40 μm, as shown in Fig. 2. Before spraying, the substrate (carbon steel, 60 mm×30 mm×5 mm) was fixed at a rustless steel cylinder by clamping fixture in spraying course, whose external diameter was 200 mm, and thickness was 4 mm. Then the substrate was blasted with corundum, whose mean diameter was 200 μm. The blasting pressure was 0.6 MPa, and the distance between the nozzle and the substrate was 100 mm. The substrate was cleaned in the acetone with ultrasonic. The spraying gun perpendicularly moved to the cylinder at the speed of 12 mm/s. The Ni-Al powders were sprayed as the prime layer and transition layer to enhance the bond strength of the coating and substrate. The typical supersonic spraying parameters of the PbTiO3 coating are shown in Table 1. 2.2 Characterization The sprayed coatings were cut and polished in order to facilitate the performance analysis. The surface and cross-section morphologies of the coating were observed by microscopic. The microstructure of the coating was analyzed by scanning electron microscopy (SEM). The chemical elements changes of the coating were analyzed by energy dispersive spectroscopy (EDS). The variation of the PbTiO3 phases in the powders and the coating was detected by X-ray diffraction (XRD, RINT-2500, Rigaku) with Cu-Ka radiation. The compounds in the coating were analyzed by X-ray photoelectron spectrograph (XPS). The XPS was performed by the ESCALAB.250Xi model with an Al-Ka line (1 486.6 eV). The density of the samples was measured by the Archimedes method, at least three samples were tested under each experimental condition and each sample was measured twice. The final density data were presented ϱ 



as the average values and standard deviations. The average grain size of two-dimensional cross-section of the coating was measured by the mean ferret diameters using an image analysis program (Matrox Inspector 2.1). The bond strength between the coating and the substrate was measured by WE-100 model universal test machine. Three points of the samples were selected, and the average value was taken as the result of the bond strength. The delicate LC material analysis meter was used to study the ferroelectric hysteresis of the PbTiO3 coating, and the HP4284A LCR meter was used to measure the dielectric constant and dielectric loss tangent. 3 Results 3.1 Morphologies Fig. 3 shows the two-dimensional and three-dimensional microscopic morphologies of the coating surface. There are no obvious cracks and big pores on the coating surface. It shows the grain shapes are obviously different. Some grains are too big to be wholly heated, and unfused grains are formed on the coating surface. Some grains are so small that the whole grain is ablated, thus the pores are generated in the coating. Some grains are suitable and fused to liquid drops to spread out beautifully on the coating. The trace of the spraying grains can be obviously seen in Fig. 3 (a). The coating contains fused grains (blue arrows pointed), unfused grains (yellow arrows pointed) and hollow parts (green arrows pointed). Though the equipment moved at a fixed speed in the spraying course, some fused grains were non-homogeneously heated. When the unfused grains impact the coating surface, they can’t spread out ϲ 



completely. In the following cooling course, the mismatch grains appear around the materials. Some overhang the coating surface, and some form pores (green arrows pointed). Whereas, most completely fused grains impact the surface uniformity and spread out freely. The micro flaws of the coating are filled up very well in the following cooling course (blue arrows pointed). The positions of the grains edge are impacted by later grains, which make them become the predisposed factors of spare space in the coating in the later spraying course (yellow arrows pointed). The hollow of the coating is selected by the green arrows. The altitude between the apex and the nadir is 47.9 μm as shown in Fig. 3 (b). Fig. 4 shows the cross-section morphology of the coating. The combination between the transition layer and the substrate, as well as the transition layer and the coating are good. Though the structure of the coating is compact, some obvious big pores appear in the spraying coating. The porosity of the coating is 0.3%, as shown in the right-side area (white framing) of Fig. 4. Some pores are formed due to the fusing grains wrapped gas in the cooling process, while some are the fusing grains spread out in a non-homogeneous form. The cracks are obvious in the transition layer, which are caused by the substrate abrasive blasting before Ni/Al transition layer was sprayed. The contents of Fe, Ba and Ti elements are stable in the coating and the substrate, but drastically reduce at the interface between the substrate and the transition layer, as well as the transition layer and the coating, as shown in Fig. 4. The different elements curves are connected, and the converted area range is very narrow. It indicates that the coating and the transition layer combines better. The coating and the transition layer, ϳ 



as well as the transition layer and the substrate are combined by the mechanical bonds. The bond strength between the PbTiO3 coating and the substrate is shown in Table 2. The average value is 58.76 MPa, which is about 10 MPa higher than that of the coating without transition layer. The transition layer increases the deposition ratio of the ceramic coating material, and improves the cementation performance between the coating and the substrate. There are alternate black and white marking at the cross sectional PbTiO3 coating. The element contents of black and white marking are analyzed by the EDS shown in Fig. 5 and Table 3. Table 3 presents the atom ratios of Pb, Ti and O. The proportion of Pb and Ti in PbTiO3 coating should be 1:1, but the actual content of Pb is obviously lower than the theoretical value. The proportion of Pb and Ti in black marking is 11.40:21.21, and 8.53:20.69 in white marking . It obviously exhibits that Pb element is heavily lost in the white marking area. The content of the entire Pb element in spraying PbTiO3 coating is lower than the theoretical ratio (1:1). Firstly, it is because that the substrate temperature increases as the spraying processing, and the Pb element involved in the PbO is volatilized. Secondly, the heat distribution of the previous spraying grains promotes the volatilization of PbO. Thirdly, the high temperature of the flame flow bakes the cooling grains. The first two factors have the same reaction between the black and the white marking materials. The difference between the black and the white marking is mainly caused by the third factor. Though the spraying gun moves at a uniform speed, the flame flow does not simultaneously sweep the previous grains at the same time. The shorter the heat time is, the less the ϴ 



Pb element is lost. The color of the less Pb element loss is black, and the more loss is white. 3.2 Phases and composition According to the XRD results , the PbTiO3 powders and the coating both contain perovskite phase, as shown in Fig. 6. The indices of crystallographic plane of the diffraction peaks are (100), (101), (110), (200), and (211), which indicate that the PbTiO3 powders are the tetragonal phase. The diffraction peaks of the coating show that the phase has transformation and more than one phase exists in PbTiO3. It can be concluded from the indices of crystallographic plane that TiO2 involves in the coating. A very broad peak at 30° probably belongs to pyrochlore-type Pb2Ti2O6 phase, which is a metastable cubic phase. It can transform to perovskite structure when heated at a higher temperature. The PbO peak is not found because PbTiO3 is decomposed into TiO2 and PbO. The evaporation temperature of PbO is 1 535ഒ, but the temperature of the spraying flame flow is above 3 500ഒ. Thus, some PbO in the coating volatilizes in the spraying course. The c/a ratio of the PbTiO3 coating is 1.065(1.064) as shown in Table 4, implying that the crystal lattice distorts. The XPS spectra of the PbTiO3 samples are shown in Fig. 7. Fig.7 (a) is the spectra of the PbTiO3 coating, and there are four obvious peaks which are Pb, Ti, O, and C. The surface atomic concentrations in the investigated samples are determined by the photoemission peak areas. The peaks corresponding to Pb (4f7/2) have three compositions observed by curve fitting, at about 138.0 eV, 137.4 eV and 136.8 eV (shown in Fig. 7 (b)). It shows that Pb exists with three different chemical ϵ 



environments in the PbTiO3 coating, and the peak at 138.0 eV belongs to PbTiO3, at 137.4 eV belongs to Pb, and at 136.8 eV belongs to PbO. The peaks corresponding to O (1s) also have three compositions, at about 531.8 eV, 530.9 eV, and 529.9 eV (shown in Fig. 7(c)). It shows that O exists in three different chemical environments in the PbTiO3 coating, the peak at 531.8 eV belongs to Fe(OH)3, at 530.9 eV belongs to PbO, and at 529.9 eV belongs to PbTiO3.The peaks corresponding to Ti (2p3/2) have two composition, at about 458.9 eV and 456.8 eV (shown in Fig. 7(d)). It shows that Ti exists with two different chemical environments in the PbTiO3 coating, and the peak at 458.9 eV belongs to PbTiO3 and at 456.8 eV belongs to TiO2. By analyzing the XPS spectra, it is found that the bonding energy of PbTiO3 exists in the three elements peak curves, and the PbTiO3 is proved to exist in the coating. Through the Pb (4f7/2) and O (1s) spectra, it can be concluded that PbO exists in the coating. It shows that the PbTiO3 powders are decomposed in the course of spraying, and partial PbO in the coating has volatilized. Through the O (1s) and Ti (2p3/2) spectra, it can be concluded that TiO2 exists in the spraying coating, and it is the second decomposed product. 3.3 Performance As everyone knows᧨PbTiO3 is a kind of ferroelectric material . The theoretical and the experimental works have indicated that the prominent ferroelectric property and the tetragonal phase in PbTiO3 stemmed from the formation of the strong covalent Pb-O bond through the hybridization of the Pb (6s) and O (2p) orbit. Ferroelectric polarization-electric-field (P-E) hysteresis curves of the PbTiO3 coating ϭϬ 



are measured at room temperature, as shown in Fig. 8. The hysteresis P-E loops measured at different frequencies show typical ferroelectric characteristics, which almost remain the same shape. The ferroelectric hysteresis is not completely symmetrical, because the Schottky barrier is formed at the lower side of the coating. At the same time, due to the inherent stress in the spraying coating, the ferroelectric hysteresis is not completely closed. The sample size is less than 100 nm, and the electric domain size is bigger than the crystal grain size, which make the 90° domain changed into 180° domain. This indicates that the 90° domain is greatly reduced, and it makes the shearing force can’t be effectively released. The spontaneous polarization of the sample is limited. The defects of the spraying coating involve cracks, pores and unfused grains, which create the depolarizing field. The depolarizing field can influence the samples’ polarized state, so the weak ferroelectric hysteresis is obtained, as shown in Fig. 8.The P-E loops are not saturated, because the charge flaw exists in the coating. Fig. 9 shows the dielectric constant (εr) at different frequencies (1 kHz, 10 kHz, 100 kHz, and 1MHz) and different temperatures (0-550 ഒ ). When the temperature changes from 0ഒ to room temperature (298 K), the dielectric constant keeps at about 180, and it is not correlated with the test frequencies. The dielectric constant obviously changes above the room temperature, and increases with the temperature raising. When the frequency is 1 kHz at 480ഒ, the dielectric constant reaches the maximum. The peak value of εr gets smaller at 494ഒ, and the temperature is corresponded with the ferroelectricity-paraelectric transition temperature. As the ϭϭ 



frequencies increasing from 1 kHz to 1 MHz, the εr decreases from 7 136 to 2 825. It is because that the oxygen induced dielectric polarization at high temperature is the dominant factor. The peak value of dielectric constant of ferroelectrics (bulk ceramics) shifts to the high temperature orientation, but the PbTiO3 coating shows a reverse tendency. These phenomena are correlated with the defects, not correlated with the diffuse phase changes [21-23]. The dielectric loss tangent (tan δ) under the same condition is shown in Fig. 10. A very sharp maximum in each curve (particularly in 100kHz and 1MHz) occurs around the critical temperature(Tc, 480ഒ), due to the increased polarizability of materials around Tc. It means the apparent dispersion exists in the conductor (coating). Moreover, all the spraying coatings are not highly compact, and the density is lower than that of the sintering ceramic. The unfused gains and gas pores can not be avoided in PbTiO3 coating, which can decrease the dielectric constant and increase the dielectric dissipation. Fig. 11 shows the relationships between the piezoelectric coefficient and the applied electrical fields. When E<2.5 kV/mm, d33 gradually increases with the E increasing. The polarization only make the 180° electric domain orient to the external electric field direction, so the d33 is small and increases slowly. When E>2.5 kV/mm, d33 rapidly increases with the E enlarging. The external electric field is bigger than the coercive field, and make the 90° electric domain (turning difficultly) orient to the external electric field direction. The d33 increases rapidly when E>3 kV/mm, and the electric domain orienting to the external electric field direction is finished, and d33 increases slowly. When E>4.25 kV/mm, the electron is ionized, and the ceramic coating is break down. ϭϮ 



Ferroelectric polarization-electric-field (P-E) hysteresis curves and the relationships between the piezoelectric coefficient and the applied electrical fields indicate that the PbTiO3 coating possesses the piezoelectric performance as the bulk ceramic. 4. Discussion The above experimental results indicate that the dense PbTiO3 spraying coating is obtained, and the coating possesses the elementary ferroelectric properties. The PbTiO3 ceramic bulk is sintered through mixing a certain proportional of PbO and TiO2 [2]. It is well known that pure and dense PbTiO3 ceramic does not exist. Using sintering for PbTiO3, PbO (melting point is 1 161 K, and steam point is 1 808 K) is volatile at high temperature, which affects the stoichiometry and electrical properties of PbTiO3 material [4, 5]. Ferroelectric properties are very sensitive to the composition and perovskite structure, which are impossible to maintain at high temperature [1]. In the plasma spraying course, the flow temperature reaches 4 000-5000ഒ [7, 20]. The PbTiO3 are decomposed into PbO and TiO2, and at the same time, large quantity PbO volatilizes. If the time is long enough, all the PbTiO3 can be decomposed, and dense PbTiO3 coating cannot be obtained [2]. In order to avoid decompose occur, the prilling was used to enlarge the size of the feed powders. The feed powders size can affect the dissolution rate of PbTiO3. The oversize and undersize feed powders all can decrease the quality of the spraying coating. The oversize feed powders can not be wholly melted, thus the number of unfused grains increases [10, 17]. While, some undersize feed powders can lead to the blockage of spraying gun, and the powders easily flush out by the anti-gas flow. Other undersize ϭϯ 



feed powders are heated to be decomposed [20]. The phenomenon can be explored as following: Assumed a grain as a ball, the grain surface temperature instantaneously reaches the melting point. The increase of center temperature depends on the energy transfer from surface to center. This is a one-dimensional unsteady heat conduction phenomenon. The heat transmission coefficient (α) is a definite value; the temperature of any point on the ball (grain) is the function of time (t1) (the time is the grain flying from spraying gun to the substrate) and semidiameter, the t1 is quite short. During this quite short time, the PbTiO3 grains cannot be completely decomposed and only part of them are decomposed to PbO and TiO2. The other grains hit and freeze on the substrate before reacting at high temperature flame flow. It is also inferred that the PbTiO3 are not completely decomposed. 5. Conclusion The structure of the coating prepared by HEPJet spraying system is dense, and its porosity is lower. There is no obvious transient area between the coating and the substrate, showing the micro-metallurgic combination. The PbTiO3 powders with tetragonal phase are decomposed into PbO and TiO2 in the spraying course. The ferroelectric hysteresis loop is weak and is not completely closed, due to the pores and the cracks in the coating. Dielectric constant and dissipation constant indicate that the PbTiO3 coating is provided with the piezoelectricity. Acknowledgment This papers is financially supported by NSFC (51275526), 973 Project ϭϰ 



(2011CB0131405), The Tribology Science Fund of State Key Laboratory of Tribology (SKLTKF13A01), Distinguished Young Scholars of NSFC (51125023), NSF of Beijing (3120001). References [1] Chen Y, Zhu JG, Xiao DQ, Qin BQ, Jiang YH. Bismuth-modified BiScO3–PbTiO3 piezoelectric ceramics with high Curie temperature. Mater Lett 2008;62:3567–3569. [2] Zhang CH, Hua Z, Gao G, Zhao S, Huang YD. Damping behavior and acoustic performance of polyurethane/lead zirconate titanate ceramic composites. Mater Design 2013;46:503-510. [3] Eglitis RI, Piskunov S, Heifets E, Kotomin EA, Borstel G. Ab initio study of the SrTiO3, BaTiO3 and PbTiO3 (001) surfaces. Ceram Int 2004;30:1989–1992. [4] Martin-Arbella N, Bretos I, Jimenez R, Calzada ML, Sirera R. Photoactivation of Sol–Gel Precursors for the Low-Temperature Preparation of PbTiO3 Ferroelectric Thin Films. J Am Ceram Soc 2011;94:396-403. [5] Du ZH, Zhu MM, Zhang TS, Ma J. Crystallization of Pb((Zn,Mg)1/3Nb2/3)O3–PbTiO3 Thin Films Via Immobilization of Pb21 Ions During Sol–Gel Process. J Am Ceram Soc 2010;93:4036-4040. [6] Piao ZY, Xu BS, Wang HD, Wen DH. Investigation of acoustic emission source of Fe-based sprayed coating under rolling contact, International Journal of Fatigue, 2013, 47: 184-188. [7] Piao ZY, Xu BS, Wang HD, Wen DH. Influence of surface nitriding treatment on rolling contact behavior of Fe-based plasma sprayed coating, Applied Surface Science, 2013, 266(1): 420-425. [8] Zhao Q, Fan ZX, Tang ZS, Meng XJ, Song JL, Wang GS, Chu JH. Highly (111)-oriented ϭϱ 



PbTiO3 films prepared by rf planar magnetron sputtering and their optical properties. Surf Coat Technol. 2002;160:173-176. [9] Chen L, Ren W, Zhu WM, Ye ZG, Shi P, Chen XF, Wu XQ, Yao X. Improved dielectric and ferroelectric properties in Ti-doped BiFeO3-PbTiO3 thin films prepared by pulsed laser deposition. Thin Solid Films 2010;518:1637-1640 [10] Roemer A, Millon E, Seiler W, Ruch D, Riche A. Correlation between structural and mechanical properties of PbTiO3 thin films grown by pulsed-laser deposition. Appl Surf Sci 2006; 252:4558-4563. [11] Mikael AK, Timothy PC, Andrew JB. Deposition of PbTiO3 films on Pt/Si substrates using pulsed laser deposition. J Eur Ceram Soc 2008;28:591-597. [12] Piao ZY, Xu BS, Wang HD, Wen DH. Influence of surface roughness on rolling contact fatigue behavior Fe-Cr alloy coatings. Journal of Materials Engineering and Performance, 2013, 22(2): 767-773. [13] Tang LW, Du PY, Han GR, Weng WJ, Zhao GL. Preparation of silver dispersed PbTiO3 film by sol-gel method. Mater Sci Eng B 2009;99:370-373. [14] Choi YC, Kim J, Bu SD. Template-directed formation of functional complex metal-oxide nanostructures by combination of sol–gel processing and spin coating. Mater Sci Eng B 2006;133:245-249. [15] Dobbelaere CD, Hardy A, Haen JD, Van den Rul H, Van Bael MK, Mullens J. Morphology of water-based chemical solution deposition (CSD) lead titanate films on different substrates: Towards island formation. J Eur Ceram Soc 2009;29:1703-1711. [16] Liu JS, Zhang SR, Yang CT, Zhou JL. Low-temperature fabrication of Pb(Zr0.52Ti0.48)O3 ϭϲ 



films using a new chemical solution deposition method without post-annealing. J Cryst Growth 2004;264:302-306. [17] Piao ZY, Xu BS, Wang HD, Wen DH. Microstructure characterization of a Fe-Cr alloy coating deposited by supersonic plasma spraying technique. Fusion Engineering and Design. 2013. 88(11):2933-2938. [18] Ignacio C, Soares AR, Yukimitu K, Moraes JCS, Malmonge JA, Nunes VB, Zanette SI, Araújo EB. Structure and microstructure of PbTiO3 thin films obtained from hybrid chemical method. Mater Sci Eng A 2003;346:223-227. [19] Ye Y, Yu SH, Huang HT, Zhou LM. A polyethylene glycol-assisted route to synthesize Pb(Ni1/3Nb2/3)O3-PbTiO3 in pure perovskite phase. J Alloy Compd 2009;480: 510-515. [20] Zhang W, Guo YM, Chen YX. Applications and Future Development of Thermal Spraying Technologies for Remanufacturing Engineering. China Surf Eng 2011;24:1-10. [21] Bandarian M, Shojaeia A, Rashidi AM. Thermal, mechanical and acoustic damping properties of flexible open-cell polyurethane/multi-walled carbon nanotube foams: effect of surface functionality of nanotubes. Polym Int 2011;60:475-482. [22] Xu Q, Zhang XF, Liu HX, Chen W, Chen M, Kim BH. Effect of sintering temperature on dielectric properties of Ba0.6Sr0.4TiO3-MgO composite ceramics prepared from fine constituent powders. Mater Design 2011;32:1200-1204. [23] Piao ZY, Xu BS, Wang HD. Investigation of spalling mechanism of the thermal sprayed coating under rolling contact by FIBದSEM, Engineering Failure Analysis, 2012,25: 106-111.

ϭϳ 



Table captions Table 1 Parameters of supersonic plasma spraying Table 2 The results of the bonding strength test of the PbTiO3 coating Table 3 Element ratio of black and white marking Table 4 Cell and Symmetry Information

ϭϴ 



Table 1 The supersonic plasma spraying parameters of PbTiO3 Supersonic plasma spraying parameters 3.2 Flow of Ar gas (m3/h) 3 0.58 Flow of H2 gas(m /h) 0.5 Flow of N2 gas(m3/h) Spraying current(A) 430 Spraying voltage(V) 150 Spraying distance(mm) 100 Powder feed rate(g/min) 35 Coating thickness(μm) 50-100

ϭϵ 



Table.2 Bonding Strength test of PbTiO3 coating No. 1 2 3 4 5 average

ϮϬ 

Bonding strength /MPa 56.8 61.1 61.7 57.9 56.3 58.76



Table.3 the element ratio of black and white marking Black marking Element

Weight%

Atomic%

Element

67.38

O

White marking Weight%

O

24.19

Ti

22.80

21.21

Ti

26.21

20.69

Pb

53.00

11.40

Pb

46.14

8.53

Totals

100.00

Totals

100.00

Ϯϭ 

27.65

Atomic% 70.78



Table.4 Cell and Symmetry Information System a Density(Dm) Space Group tetragonal 3.8993 7.820 P4/mmm(No.123)

ϮϮ 

c 4.1532

Density(Dx) 7.970



Fig captions Fig.1. The PbTiO3 feedstock powders pattern Fig.2. The abridged general view of spraying gun Fig.3. The two-dimension and three-dimensional morphologies of PbTiO3 coating(a) two-dimension morphologies; (b) three-dimensional altitude distribution Fig.4. The observation of the PbTiO3 coating (a) line scanning on the coating cross-section (b) coating porosity ratio Fig.5. The black and white EDS of PbTiO3 coating:(a) element distribution of black marking (b) element distribution of white marking Fig.6. The XRD spectra of the powder and coating Fig.7. The XPS spectra of element in the BaTiO3 coating: (a) PbTiO3 (b) Pb (c) O1s Ϯϯ 



(d) Ti Fig.8. Ferroelectric polarization-electric-field (P-E) hysteresis curves of the PbTiO3 coating with different frequencies Fig.9. The dielectric constant of PbTiO3 Fig.10. The change of piezoelectric coefficient (d33) with the different electric fields

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Highlights



PbTiO3 coatings were successfully sprayed by employing the HEPJet spraying system.

 The PbTiO3 coating microstructure was studied. 

The coating exhibits the ferroelectric-piezoelectric properties at room temperature.

Ϯϱ