Structural and temperature dependent dielectric properties of nanocrystalline PbTiO3 synthesized through auto-igniting combustion technique

Journal Pre-proof Structural and temperature dependent dielectric properties of nanocrystalline PbTiO3 synthesized through auto-igniting combustion technique M.K. Suresh, J.K. Thomas PII:

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https://doi.org/10.1016/j.solidstatesciences.2019.106025

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Solid State Sciences

Received Date: 15 June 2019 Revised Date:

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Please cite this article as: M.K. Suresh, J.K. Thomas, Structural and temperature dependent dielectric properties of nanocrystalline PbTiO3 synthesized through auto-igniting combustion technique, Solid State Sciences (2019), doi: https://doi.org/10.1016/j.solidstatesciences.2019.106025. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Masson SAS.

Structural and temperature dependent dielectric properties of nanocrystalline PbTiO3 synthesized through auto-igniting combustion technique M.K. Suresh1,* and J.K. Thomas2 1

Department of Physics, St. Thomas College, Ranni, Pathanamthitta, India-689673

2

Department of Physics, Mar Ivanios College, Thiruvananthapuram, India-695015

Abstract Nanocrystalline PbTiO3 has been synthesized through an auto-ignited combustion method. The structure of the powder was examined using X-ray diffraction, thermo gravimetric analysis, differential thermal analysis and Fourier Transform Raman spectroscopy. Rietveldrefinements were performed in order to determine the structural parameters of the material. The crystalline size of the particle was calculated using Scherrer formula and examined using transmission electron microscopy. The nanopowder could be sintered to 95 % of the theoretical density at 1100 °C for a short duration of time 2 h. The microstructure of the sintered surface was examined using scanning electron microscopy. The variation of dielectric properties of the specimen was studied at different frequencies and temperatures. A maximum of dielectric constant 30901 obtained at 50 Hz when the temperature is 500 oC (near transition temperature, Tc). The excellent dielectric properties of the PbTiO3 ceramics at different conditions assure the sample is useful to many electronic devices.

KEYWORDS: A. ceramics, B. nanoparticles, C. combustion synthesis, D. dielectric properties, E. ferroelectric *Corresponding Author: Dr. Suresh M.K.,

E-mail: [email protected] Phone: +91-9446738693

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1. Introduction Lead titanate (PbTiO3), which exhibits a perovskite structure and a very high Curie temperature of 490 °C, belongs to the most important ferroelectric and piezoelectric families [1]. In earlier studies, its symmetry at room temperature was correctly determined to be tetragonal. The lattice parameters were measured to be a = 3.89 Å and c = 4.13 Å and which were later corroborated by other authors [2, 3]. This gives a unit cell tetragonality ratio (c/a) of 1.062 for lead titanate. On heating to approximately 490 °C, the crystal undergoes a first-order phase transition to a cubic phase. Shirane et al and later Mabud et al carried out temperature-dependent measurements of the lattice parameters, revealing that the volume of the unit cell showed a slight decrease up to the transition temperature, beyond which it rose [4, 5]. The separation of the c and a axes became smaller with temperature in the tetragonal phase, with a sudden decrease to zero at the phase transition point. PbTiO3 exhibits cubic perovskite structure and non-polar behaviors above the Curie temperature. This material has been applied to many useful electronic devices such as high energy capacitors, nonvolatile memories, ultrasonic sensors, infrared detectors, other electro-optic devices, etc. by utilizing their excellent dielectric, ferroelectric and piezoelectric properties exhibit at different frequencies and temperatures. Various techniques have been applied to prepare PbTiO3 powders [6-12]. Among the available solution-chemistry routes, combustion technique is capable of producing nanocrystalline powders of oxide ceramics, at a lower calcination temperature in a surprisingly short time [13-16]. In this paper, for the first time, the synthesis, characterization and vibrational spectroscopic studies of nanocrystalline PbTiO3 powder prepared through auto-ignited combustion method [17, 18] is reported. The sintering behavior as well as the response of dielectric properties to different temperatures at radio frequency range is discussed in detail in this paper.

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2. Experimental The basic step for the preparation of PbTiO3 by the combustion method is to prepare an aqueous solution containing Pb and Ti ions. Pb ions were prepared by dissolving high purity Pb(NO3)2⋅6H2O (99 %, Himedia, India) in double distilled water. Ti ions were prepared by dissolving C12H28O4Ti (>98 %, Acros Organics, USA) in ethyl alcohol. To obtain the precursor complex, the stoichiometric solution containing Pb and Ti ions was mixed with citric acid solution, keeping the citric acid to the cation ratio unity. Citric acid was used as complexing agent. Conc. HNO3 was then added to the precursor. The product was stirred well for uniform mixing. Liquor ammonia was added to the solution to adjust the oxidant-fuel ratio to unity and it acts as the fuel for combustion. The solution was heated on a hot plate at ~250 °C, it boils and undergoes dehydration followed by decomposition, leading to a smooth deflation, producing dark foam. On persistent heating the foam gets auto-ignited giving a voluminous white fluffy powder of PbTiO3 with traces of black organic impurities. The structure of the as-prepared powder, the sample heated at 600 °C for 20 min and sintered at 1100 °C for 2 hours were examined using X-ray Diffractometer with Nickel filtered Cu Kα radiation (Model- Philips Expert Pro). The thermo gravimetric analysis (TGA) and differential thermal analysis (DTA) were carried out using Perkin-Elmer TG/DT thermal analyzer in the range 30-1200 °C at 20 °C/min in nitrogen atmosphere. The Fourier Transform-Raman spectrum of the nanocrystalline PbTiO3 heated at 600 °C for 20 min was carried out at room temperature in the wave number range 50 – 900 cm-1 using Bruker RFS/100S Spectrometer at a power level of 150 mW and at a resolution of 4 cm-1. The samples were excited with an Nd:YAG laser lasing at 1064 nm and the scattered radiations were detected using Ge detector. The transmission electron micrograph of PbTiO3 nanopowder and their corresponding selected area diffraction patterns were taken using FEI Tecnai G2 S-TWIN 300 kV HRTEM. The sintered samples were polished and the experimental densities were estimated by the Archimedes method. The surface morphology of the sintered PbTiO3 sample was studied by Scanning 3

Electron Microscope (SEM, JEOL Model 6390 LV). The low frequency dielectric properties were studied using an LCR meter (Hioki-3532-50) in the frequency range 45 Hz – 5 MHz and high quality temperature controlled oven was used for temperature dependent studies. 3. Results and Discussion Fig. 1(a)-(c) show the X-ray diffraction (XRD) patterns of the as-prepared PbTiO3 nanopowder, the powder heated at a temperature of 600 °C for 20 min and the sample sintered at 1100 °C for 2 h, respectively. The XRD pattern of the as-prepared sample showed that the PbTiO3 crystalline phase (ICDD file 74-2495) was formed by the combustion method along with Pb2O3 (ICDD file 360725), marked as (#), as minor phase. The organic impurities contained in the as-prepared powder, as a result of the combustion process, were completely eliminated when it is heated up to 600 °C. When the as-prepared powder was heated to 600 °C for 20 min, the (212) reflection peak of Pb2O3 was disappeared. Moreover, the (120) reflection peak of Pb2O3 disappeared when the sample was sintered at 1100 °C for 2 h. It is found that all the diffraction peaks are well consistent with standard powder XRD pattern of tetragonal perovskite with P4mm space group. The lattice constants a and c were calculated based on the major reflections for the as-prepared powder, the powder heated at 600 oC for 20 min and the sintered sample. All calculated lattice constants were summarized in Table 1. These parameters agree relatively well with the values given in the ICDD file 74-2495 (a = 3.900 Å and c = 4.150 Å) and the Crystallographic Open Database Card No. 1521255 (a = 3.903 Å, c = 4.135 Å, cell volume= 63.016 Å3) [19]. The lattice strain (c/a) for each condition was also included in Table 1. For all the conditions, the c/a ratios were smaller than bulk specimen reported in literature (c/a = 1.065). However, these values agree with those reported by other researchers for PbTiO3 obtained from chemical methods [19, 20]. The average crystalline size calculated from full width half maximum (FWHM) using the Scherrer formula for the major (hkl) reflections of as-prepared PbTiO3 nanopowder and the powder heated at 600 oC/20 min are given in Table 1.

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The XRD patterns were analyzed with the help of FullProf program by employing Rietveld refinement technique [21]. The refined XRD pattern of powder heated at 600 oC for 20 min is shown in Fig. 2. It can be observed that all the observed peaks could be well refined. The experimental points are given as dot (•) and theoretical data are shown as solid line. Difference between theoretical and experimental data is shown as bottom line. The vertical lines represent the Bragg’s allowed peaks. The refined cell parameters are found to be a = b = 3.905(0.000) Å and c = 4.139 (0.000) Å. The unit cell volume is found to be 63.119(0.000) Å. The goodness of fit parameters are found to be Rp= 26.7, Rwp= 25.7, Rexp=13.3, RBragg= 6.57, Rf = 5.13 and χ2 = 3.84. The axial ratio c/a is found to be 1.060 which is similar to experimentally reported value. The average crystalline size calculated from the refined values using the Scherrer formula is found to be ~62 nm. The DTA and TGA curves up to 1200 °C of the PbTiO3 nanopowder are shown in Fig. 3. The TGA curve shows a weight loss of ~10 % for a temperature range of 30-1200 °C. The weight loss of ~2% up to 1050 °C is due to the liberation of various gases (such as water vapor, CO, CO2, NO2, etc.) and elimination of organic impurities present in the sample. The decomposition of additional phase of Pb2O3 may also responsible for the steady weight loss in the whole temperature range. Considerable weight loss observed beyond 1050 °C is due to partial evaporation of lead oxide. A strong exothermic peak observed in DTA between 30 to 100 °C is accompanied by the release of heat due to the evaporation of water content and combustion of the carbonaceous residue from the decomposition of complexes. The enthalpy changes observed in the DTA curve at different temperatures coincide with the TGA curve. The Raman spectrum of PbTiO3 nanoparticles, over the wavenumber range 50-900 cm-1, is shown in Fig. 4. The observed spectral data and their assignments are given in Table 2. The Raman spectrum of the compound PbTiO3 exactly matches with the earlier reports [22-27]. The observed bands are assigned on the basis of the report by Burns and Scott [28]. The compound belonging to the

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tetragonal symmetry with space group P4mm has 12 optical modes, namely 3A1(TO) + 3A1(LO) + 3E(TO) + 3E(LO), where LO and TO refer to longitudinal and transverse optical modes. The lowest wavenumber band, the ferroelectric soft mode E(1TO) is observed at 85 cm-1 as an intense band. The A1(1TO) mode at 122 cm-1 is found to have a shoulder on the lower wavenumber side. Foster et al have reported that the anomalous shape of the band is due to the anharmonicity in the effective interatomic potential [29, 30]. Recently, studies by Cho and Jang on single-crystal PbTiO3 concluded that the anomalous scattering intensity is not due to anharmonicity of the potential well but is due to the thermodynamically stable lattice defects [31]. The medium intense band at 147 cm-1 is due to the E(1LO) mode of vibration. Of the two highly intense bands at 284 and 212 cm-1, the band at 212 cm-1 is due to mixture of A1(1LO) and E(2TO). The band at 289 cm-1 originates due to the Raman active B1 and E modes of the C4υ symmetry. The A1(2TO), A1(TO) + E(2LO), E(3TO) and A1(3TO) are observed at 345, 445, 503 and 615 cm-1, respectively. The highest wavenumber band, the E(3LO) band is observed as a weak broad band at 728 cm-1. Fig. 5(a) and 5(b) show the TEM image of the PbTiO3 nanopowder and its selected area electron diffraction (SAED) pattern, respectively. The TEM image of the PbTiO3 nanopowder shows well faceted regular shaped particles of sharp boundaries of submicron size 50-75 nm. Individual crystallites appear well bonded with few voids in between. The ring nature of the Electron Diffraction Pattern is indicative of the poly crystalline nature of the crystallites. The sintering behavior of the nanocrystals of PbTiO3 powders synthesized through the combustion technique was studied. For obtaining sintered pellets, 5 wt% polyvinyl alcohol (PVA) was added to the nanopowder of PbTiO3 as a binder and again ground well and dried. The powder was then pressed in the form of cylindrical pellets at a pressure of 100 MPa using a hydraulic press and the relative green density of the specimens used for the sintering study was around 55 %. The compacted pellets were then subjected to sintering at different temperatures for 2 h in a controlled heating schedule of 4 °C /min. The sample was then furnace cooled to room temperature. The sintered samples were 6

polished and the experimental densities were estimated by Archimedes method. Fig. 6 shows the variation of experimental density of PbTiO3 ceramics as a function of sintering temperature. The density is increasing with the increase of temperature and a maximum relative density of 95.4% (7.61 g/cm3) is obtained for the sample sintered at 1100 °C for 2 h. The high sintered density obtained in a relatively shorter sintering time may be attributed to the enhanced kinetics due to the small degree of agglomeration and ultra-fine nature of the powder. Surface morphology of the sintered PbTiO3 specimen was examined using SEM and is shown in Fig. 7. The pellet polished and thermally etched at 1050 °C for half an hour was used for Scanning Electron Microscopy analysis. The image clearly shows that the sample is well sintered with minimum porosity. It can be seen that two types of grains are present in the image and they are well dispersed by well-defined grain boundaries. One type of grains is “bar” and “plate-let” shaped and others are agglomerated grains. The formation of different types of grains may be due to the volatilization of PbO at higher sintering temperature and it is evident from the TGA/DTA result given in Fig. 3. The EDS spectrum of the surface of sintered pellet is given in Fig. 8 and it gives the stoichiometric concentrations of the constituent elements present in the surface. The dielectric constant (εr) and loss factor (tan δ) values of the PbTiO3 pellets sintered from the nanopowder were studied in the frequency range 45 Hz to 5 MHz at different temperatures with silver electrodes on both sides of the circular disc. For low frequency dielectric studies, pellet of diameter ~11 mm and thickness ~2 mm was made in the form of a disc capacitor with the specimen as the dielectric medium. Fig. 9 shows the variation of dielectric constant (εr) and dielectric loss (tan δ) with frequency for PbTiO3 ceramics at room temperature (~25 oC). Table 3 shows the dielectric constant (εr) and dielectric loss (tan δ) exhibited at different frequencies at room temperature. The dielectric constant decreases from 562 to 166 and the loss factor decreases from the order of 10-1 to 10-3, when the frequency increases from 45 Hz to 5 MHz. Fig. 10 shows the variation of dielectric constant (εr) with

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frequency at different temperatures. The dielectric constant (εr) initially shows a decreasing trend with increase in frequency and then becomes almost constant after 100 kHz, which is a general feature of polar dielectric materials [32]. This behavior may be attributed to the dipole relaxation phenomena. This is because of the inability of the electric dipoles to be in pace with the frequency of applied electric field. That is, the polarizations in a material do not occur instantaneously with the application of the electric field due to the inertia of the dipoles. The temperature dependence of dielectric constant measured at different frequencies (1 kHz, 10 kHz, 100 kHz and 1 MHz) for PbTiO3 is shown in Fig. 11. It can be seen that the PbTiO3 sample is found to exhibit a normal ferroelectric behavior, i.e., the value of the dielectric constant increases gradually with an increase in temperature and passes through a maximum (transition temperature, Tc) around 490 oC, and then decreases. A maximum of dielectric constant 30901 obtained at 50 Hz when the temperature is 500 oC (near transition temperature, Tc). It is seen that dielectric constants of 13398, 4993, 2215 and 1562 are obtained at 1 KHz, 10 KHz, 100 KHz and 1 MHz, respectively, near Tc. Beyond Tc, the dielectric constant suddenly falls into lowest value. The excellent dielectric properties at different frequencies and temperatures show that the PbTiO3 ceramics are useful to many electronic devices. 4. Conclusion Nanocrystalline PbTiO3 was synthesized in surprisingly short duration of time through an auto-ignited combustion method. The X- Ray diffraction studies have shown that all the diffraction peaks are well consistent with standard powder XRD pattern of tetragonal perovskite with P4mm space group. Diffraction data was quantitatively analyzed using the Rietveld refinement approach. The structure of the nanopowders has been analyzed using TGA, DTA and FT- Raman spectroscopy. The TEM investigations showed that the particle size is in between 50 and 75 nm. The nanoparticles of PbTiO3 could be sintered to 95% of the theoretical density at temperature 1100 °C for a short duration of time 2 h. The microstructure of the sintered surface examined using SEM indicates that the PbO is volatilizing at higher temperature. The dielectric properties of PbTiO3 were studied as a function of 8

frequency and temperature. The maximum dielectric constant value is obtained near transition temperature, Tc. A maximum of dielectric constant 30901 obtained at 50 Hz when the temperature is 500 oC (near Tc). The excellent dielectric properties at different frequencies and temperatures show that the PbTiO3 ceramics are useful to many electronic devices.

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11. G. Xu, W. Jiang, M. Qian, X.X. Chen, Z.B. Li, G.R. Han, Hydrothermal Synthesis of Lead Zirconate Titanate Nearly Free-Standing Nanoparticles in the Size Regime of about 4 nm, Cryst. Growth Des. 9 (2009) 13–16. 12. Z.W. Yang, X.G. Huang, G. Yang, Q. Xie, B. Li, J. Zhou, L.T. Li, Preparation and photonic bandgap properties of lead lanthanum titanate inverse opal photonic crystals, J. Alloys Compd. 468 (2009) 295–298. 13. Bhaduri S., Bhaduri S.B. and Zhou E.J., Auto ignition synthesis and consolidation of Al2O3– ZrO2 nano/nano composite powders, J. Mater. Res. 13, 1998, 156-165. 14. J.J. Kingsle, K. Suresh, K.C. Patil, Combustion synthesis of fine-particle metal aluminates, J. Mater. Sci. 25 (1990) 1305-1312. 15. M.K. Suresh, J.K. Thomas, H. Sreemoolanadhan, C.N. George, A. John, S. Solomon, P.R.S. Wariar, J. Koshy, Synthesis of nanocrystalline magnesium titanate by an auto-igniting combustion technique and its structural, spectroscopic and dielectric properties, Mater. Res. Bull. 45 (2010) 761–765. 16. M.K. Suresh, J.K. Thomas, H. Sreemoolanadhan, C.N. George, A. John, S. Solomon, P.R.S. Wariar, J. Koshy, Structural and dielectric studies of nanocrystalline calcium substituted magnesium titanate synthesized through an auto-igniting combustion technique, Int. J. Appl. Ceram. Technol. 9(2) (2012) 366-373. 17. J. James, R. Jose, A.M. John, J. Koshy, Single step process for the synthesis of nanoparticles of ceramic oxide powders, US Patent No.6761866; 13 July 2004a. 18. J. James, R. Jose, A.M. John, J. Koshy, Single step process for the synthesis of nanoparticles of ceramic oxide powders, US Patent No.6835367; 28 Dec. 2004b. 19. M. Maeda, H. Ishida, K.K.K. Soe, I. Suzuki, Preparation and Properties of PbTiO3 Films by Sol-Gel Processing, Jpn. J. Appl. Phys. 32 (1993) 4136-4140. 20. W.G. Liu, L.B. Kong, L.Y. Zhang, X. Yao, Study of the surface layer of lead titanate thin film by x-ray diffraction, Solid State Commun. 93 (1995) 653-657. 21. R.A. Young, The Rietveld Method International Union of Crystallography, Oxford University Press, New York, 1996. 22. Z.C. Feng, B.S. Kwak, A. Erbil, L.A. Boatner, Difference Raman spectra of PbTiO3 thin films grown by metalorganic chemical vapor deposition, Appl. Phys. Lett., 62 (1993) 349-351. 23. S.-H. Lee, H.M. Jang, S.M. Cho, G.-C. Yi, Polarized Raman scattering of epitaxial PbTiO3 thin film with coexisting c and a domains, Appl. Phys. Lett. 80 (2002) 3165-3167.

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24. T. Zhu, G. Han, G. Zhao, Z. Ding, A Preliminary Raman Investigation of the Lead Titanate Thin Films via Sol-Gel Process, J. Mater. Sci. Technol. 13 (1997) 306-308. 25. A. Sakai, K. Umezawa and S. Tanizaki, Preparation of BaTiO3 and PbTiO3 Thin films by Electron Beam Evaporation Method, J. Kor. Phy. Soc. 29 (1996) S624-S627. 26. T. Yu, Z.X. Shen, J.M. Xue, J. Wang, Nanocrystalline PbTiO3 powders from an amorphous PbTi-O precursor by mechanical activation, Mater. Chem. Phy.75 (2002) 216-219. 27. I. Szafraniak, M. Polomska, B. Hilczer, XRD, TEM and Raman scattering studies of PbTiO3 nanopowders, Cryst. Res. Technol. 41 (2006) 576-579. 28. G. Burns, B.A. Scott, Lattice Modes in Ferroelectric Perovskites: PbTiO3, Phys. Rev. B 7 (1973) 3088–3101. 29. C.M. Foster, M. Grimsditch, Z. Li, V.G. Karpov, Raman line shapes of anharmonic phonons, Phys. Rev. Lett. 71 (1993) 1258–1260. 30. C.M. Foster, Z. Li, M. Grimsditch, S.-K. Chan, D.J. Lam, Anharmonicity of the lowestfrequency A1(TO) phonon in PbTiO3, Phys. Rev. B 48 (1993) 10160–10167. 31. S.M. Cho, H.M. Jang, Softening and mode crossing of the lowest- frequency A1 (transverseoptical) phonon in single-crystal PbTiO3, Appl. Phys. Lett. 76 (2000) 3014-3016. 32. B. Jaffe, W.R. Cook, H. Jaffe, Piezoelectric Ceramics, Academic Press, NewYork, 1971.

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Figure captions Figure 1

XRD patterns of PbTiO3 ceramic; (a) as-prepared (b) heated at 600 °C/20 min (c) sintered at 1100 °C/2h

Figure 2

XRD pattern along with Rietveld refinement for the sample PbTiO3 heated at 600 °C/20 min

Figure 3

DTA/TGA trace of PbTiO3 nanopowder

Figure 4

Raman spectrum of PbTiO3 nanocrystal

Figure 5

(a) TEM image of PbTiO3 nanocrystals and (b) its SAED pattern

Figure 6

Variation of experimental density with sintering temperature

Figure 7

SEM image of sintered PbTiO3 ceramic

Figure 8

EDS spectrum of sintered PbTiO3 specimen

Figure 9

Variation of dielectric constant and loss factor with frequency at room temperature

Figure 10

Variation of dielectric constant (εr) with frequency at different temperatures

Figure 11

Variation of dielectric constant (εr) with temperature at different frequencies

Table Captions Table 1

Lattice parameters and crystalline size of PbTiO3 nanoparticles at different temperatures

Table 2

Spectral data of the Raman spectrum of PbTiO3 and its assignments

Table 3

Dielectric constant (εr) and dielectric loss (tan δ) of PbTiO3 exhibited at different frequencies at room temperature

Table 1 Lattice parameters and crystalline size of PbTiO3 nanoparticles at different temperatures Powder

Lattice constants (Å)

Lattice

Cell volume Crystalline

a

c

strain (c/a)

(Å)3

size (nm)

As-prepared

3.8797

4.1204

1.0620

62.0206

43

Heated at

3.8791

4.1132

1.0603

61.8930

47

3.8835

4.1169

1.0601

62.0893

--

condition

600 oC/ 20 min Sintered at o

1100 C/ 2 h

Table 2 Spectral data of the Raman spectrum of PbTiO3 and its assignments PbTiO3 (cm-1) Band assignments 728 vwbr

E(3LO)

615 s

A1(3TO)

503 s

E(3TO)

445 m

A1(2TO) + E(2LO)

345 w

A1(2TO)

289 vs

B1+E

212 vs

A1(1LO) + E(2TO)

147 m

E(1LO)

122 w

A1(1TO)

85 s

E(1TO)

Table 3 Dielectric constant (εr) and dielectric loss (tan δ) of PbTiO3 exhibited at different frequencies at room temperature Physical

Frequency

parameters

50 Hz

1 kHz

100 kHz

1 MHz

5 MHz

εr

561.90661

369.09581

183.31011

167.09832

165.91529

tan δ

2.316x10-1

2.074 x10-1

1.118 x10-1

3.238 x10-2

6.115 x10-3

Highlights of the paper


Nanocrystalline PbTiO3 powder prepared using an auto-ignited combustion method is reported for the first time.
Nanocrystalline PbTiO3 powder can be prepared at a lower temperature of ~300 ᵒC in a surprisingly short time of ~1 hr.
Most of the secondary peaks are eliminated when it is subjected to higher temperatures.
The high sintered density of 95.4% (7.61 g/cm3) is obtained for the sample sintered at 1100 °C in a relatively shorter sintering time of 2 h.
The dielectric constant value of 30901 near transition temperature, Tc, at 50 Hz obtained is the highest value which is ever reported.
This material can be applied to many useful electronic devices such as high energy capacitors, nonvolatile memories, ultrasonic sensors, infrared detectors, other electrooptic devices, etc. by utilizing their excellent dielectric and ferroelectric properties.

Conflict of Interest and Authorship Conformation Form I, Dr. Suresh M.K., the corresponding author of the manuscript entitled “Structural and temperature dependent dielectric properties of nanocrystalline PbTiO3 synthesized through auto-igniting combustion technique” submitted in the Journal Solid State Sciences confirms on behalf of all authors that o All authors have participated in (a) conception and design, or analysis and interpretation of the data; (b) drafting the article or revising it critically for important intellectual content; and (c) approval of the final version. o This manuscript has not been submitted to, nor is under review at, another journal or other publishing venue. o The authors have no affiliation with any organization with a direct or indirect financial interest in the subject matter discussed in the manuscript o The following authors have affiliations with organizations with direct or indirect financial interest in the subject matter discussed in the manuscript: Author’s name 1. Dr. Suresh M.K.

Affiliation Assistant Professor, Department of Physics, St. Thomas College, Ranni, Pathanamthitta, Kerala, India-689673 E-mail: [email protected], Phone: +91-9446738693

2. Dr. J.K. Thomas

Associate Professor, Department of Physics, Mar Ivanios College, Thiruvananthapuram, Kerala, India-695015 E-mail: [email protected], Phone: +91-9447205190