Structural and dielectric properties of Lead Magnesium Niobate and Ti-doped Lead Magnesium Niobate at room temperature

Materials Today: Proceedings xxx (xxxx) xxx

Contents lists available at ScienceDirect

Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr

Structural and dielectric properties of Lead Magnesium Niobate and Ti-doped Lead Magnesium Niobate at room temperature Sidharth Kashyap a,⇑, S.C. Bhatt a, Manish Uniyal a, Gambheer Singh Kathait b a b

Department of Physics, Hemvati Nandan Bahuguna Garhwal University, Srinagar Garhwal, Uttarakhand 246174, India Department of Instrumentation Engineering (USIC), Hemvati Nandan Bahuguna Garhwal University, Srinagar Garhwal, Uttarakhand 246174, India

a r t i c l e

i n f o

Article history: Received 11 December 2019 Accepted 2 January 2020 Available online xxxx Keywords: Relaxor ferroelectrics Perovskite Sintering Microstructure Dielectric study

a b s t r a c t Lead based relaxor ferroelectric like Lead Magnesium Niobate and their binary solid solutions with Lead Titanate have great interest of research because of their significant and excellent dielectric, piezoelectric and electrostrictive properties. In the present work, the Lead Magnesium Niobate (PMN) and Lead Magnesium Niobate-Lead Titanate (0.75PMN-0.25PT) were prepared through solid state reaction method with double sintering process at 1200 °C for 6 hr. XRD data shows the pervoskite structure of the prepared sample. SEM report of PMN and 0.75PMN-0.25PT shows the different microstructure with dense grains. Dielectric study of PMN and 0.75PMN-0.25PT shows the effect of addition of PT content on electrical properties at room temperature. Ó 2020 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of the scientific committee of the International Conference on Advanced Materials and Nanotechnology.

1. Introduction Lead Magnesium Niobate Pb(Mg1/3Nb2/3)O3 i.e. PMN is a complex Pb(B0 ,B00 )O3 type perovskite compound known as relaxor ferroelectric material. The main characteristic of dielectric properties of PMN is the maximum of dielectric constant taking placed at negative temperature with diffuse phase transition [1,2]. It exhibits strong electrostrictive performance compared to other materials due to its high dielectric constant at low temperature. Because of the high dielectric constant, outstanding electrostrictive property and lower sintering temperature of PMN make it important for multilayer capacitors, actuators and electro-optic device applications [3,4]. The phase transition temperature and maximum of dielectric constant can be shifted towards the higher temperature range when PbTiO3 is added to Lead Magnesium Niobate in proper stoichiometry. The temperature of maximum dielectric constant shifts up from 10 °C (20000) in pure Lead Magnesium Niobate to 40 °C in 0.9PMN–0.1PT, under the application of electric field of frequency 100 Hz [5]. PMN-PT is a relaxor ferroelectric material which has been widely investigated due to their advantageous dielectric, piezoelectric and electrostrictive properties and widely used as multilayer capacitors, electrostrictive actuators, sensors ⇑ Corresponding author. E-mail address: [email protected] (S. Kashyap).

and many other electronic and biomedical devices [6,7]. PMN-PT is a binary solid solution of relaxor ferroelectric Lead Magnesium Niobate and normal ferroelectric Lead Titanate (PT). These relaxor ferroelectrics have ABO3 type crystal structure with mixed B-site. The properties of (1  x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 ceramics are changed as Ti concentration varies. A ceramic with low content of Ti behaves as a relaxor ferroelectric and with high amount of Ti the ceramic becomes a normal ferroelectric [8]. Hence the solid solution (1  x)PMN-xPT possess different type of phase transition with different values of x. The dielectric property of the material is directly depending on the density of prepared sample. Densification of material is controlled by preparation and sintering process. Density of this type of PMN based perovskite will be increased when sintered in the temperature range 1200–1300 °C. It is difficult to prepare pure PMN-PT because of volatile nature of lead oxide. Therefore excess amount of MgO and PbO is added to starting reagent in stoichiometric proportion. It has been investigated that excess amount of MgO increase the dielectric and microstructural properties with reduced pyrochlore phase. The PMNPT relaxor ferroelectric exhibit a morphotropic phase boundary (MPB) separating the rhombohedral and tetragonal phases. The MPB is located between x = 0.30 and 0.40 [9]. Compositions in the (1  x)PMN-xPT with x greater than approximately 0.30 are piezoelectric [10,11]. On the basis of experimental results, it is found that, at the morphotropic phase boundary, the dielectric and piezoelectric proper-

https://doi.org/10.1016/j.matpr.2020.01.032 2214-7853/Ó 2020 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of the scientific committee of the International Conference on Advanced Materials and Nanotechnology.

Please cite this article as: S. Kashyap, S. C. Bhatt, M. Uniyal et al., Structural and dielectric properties of Lead Magnesium Niobate and Ti-doped Lead Magnesium Niobate at room temperature, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.01.032

2

S. Kashyap et al. / Materials Today: Proceedings xxx (xxxx) xxx

ties are reached to maximum hence making the material significant for actuator and sensor applications [12,13]. 2. Experimental High purity oxides PbO, Nb2O5, MgO and TiO2 were used as starting material in stoichiometric proportion. The Lead Magnesium Niobate and Lead Magnesium Niobate-Lead Titanate both were prepared by Solid State Reaction method as following.

nol medium for 2 h and then calcined at 1110 °C for 5 h. The intermittent product MgNb2O6 was again mixed with PbO and TiO2 in stoichiometric proportion. Extra 8% amount of PbO was also added because of its volatile nature at high temperature. The mixed powder was calcined at 920 °C for 2 h in closed alumina crucible. The prepared sample was pelletized without adding any binder and then sintered at 1200 °C for 6 h. 3. Characterization of samples

2.1. Preparation of Lead Magnesium Niobate (PMN)

3.1. XRD analysis

The Lead Magnesium Niobate i.e. PMN was prepared by two step solid state reaction method [14]. In the first step of reaction, powders of PbO and Nb2O5 were weighed in stoichiometric proportion and mixed by the agate mortar and pestle in ethanol medium for 2 h with 5% excess amount of PbO to compensate the loss of Lead at high temperature. The mixed sample was calcined at 820 °C for 3 h. The intermittent product Pb3Nb2O8 was mixed with excess 2% MgO in stoichiometric proportion and calcined again at 800 °C for 3 h. The final product was pre-sintered at 900 °C for 6 h. The pre-sintered powder was pressed to prepare pellets of the sample without adding any binder. Prepared Pellets were sintered at 1150 °C for 6 h to get perovskite phase.

X-ray diffraction method was used to identify the perovskite phases in the prepared sample. XRD patterns of Lead Magnesium Niobate and Lead Magnesium Niobate-Lead Titanate show that pyrochlore phase can be reduced by high temperature sintering process. Figs. 1 and 2 shows the XRD pattern of Lead Magnesium Niobate and Lead Magnesium Niobate-Lead Titanate. The diffraction intensity was measured from 20° to 80° at room temperature. From further phase study of PMN and (1  x)PMN-xPT (for x = 0.25), it is clear that they exhibits cubic and rhombohedral (pseudocubic) crystal structure at room temperature respectively.

2.2. Preparation of Lead magnesium Niobate-Lead Titanate (0.75PMN0.25PT) The Lead Magnesium Niobate-Lead Titanate for x = 0.25 was prepared by columbite precursor method [15]. In this method, the stoichiometric amount of MgO and Nb2O5 were mixed in etha-

3.2. SEM analysis SEM was used to study the grain size, crystalline size and surface morphology of the prepared sample. The scanning electron micrographs of the PMN and 0.75PMN-0.25PT heated at different temperatures are shown in the figures. The SEM images show that grains are arranged very close to each other. This compact form of grains is responsible for increase in density. Fig. 3(a) shows the grain size of 1.5 mm with very small number of pores due to evaporation of lead from the sample. Fig. 3(b) shows the polygonal shaped grains with grain size between 1.6 mm to greater than 2 mm. The average grain size and densities of prepared samples are given in the Table 1. 4. Dielectric study

Fig. 1. XRD pattern of the Lead Magnesium Niobate calcined at 900 °C.

The FLUKE PM6306 programmable Automatic RCL meter was used for precise measurements of resistance, capacitance and inductance. Variation in dielectric constant, electrical conductivity and tangent loss of PMN and 0.75PMN-0.25PT has been studied with different frequencies ranging from 1 KHz to 1 MHz at room temperature. It is investigated that the dielectric constant gradually decreases with increase in frequency. The decrease in dielec-

Fig. 2. XRD patterns of the 0.75PMN-0.25PT (a) calcined at 920 °C for 2 h and (b) sintered at 1200 °C for 6 h with reduced pyrochlore phases.

Please cite this article as: S. Kashyap, S. C. Bhatt, M. Uniyal et al., Structural and dielectric properties of Lead Magnesium Niobate and Ti-doped Lead Magnesium Niobate at room temperature, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.01.032

3

S. Kashyap et al. / Materials Today: Proceedings xxx (xxxx) xxx

Fig. 3. SEM micrographs of (a) PMN and (b) 0.75PMN-0.25PT at sintering temperature 1150 °C and 1200 °C respectively. Table 1 The average grain size and densities of PMN and 0.75PMN-0.25PT. Sample

Sintering temperature

Density (gm/cm3)

Average grain size (mm)

PMN 0.75PMN-0.25PT

1150 °C 1200 °C

5.03 9.2

1.5 2.5

Table 2 The values of dielectric constant, loss tangent and electrical conductivity of PMN with different frequencies at room temperature. Sample PMN

Frequency (KHz)

Dielectric Constant (ƐRT)

Loss Tangent (tan d)

Electrical Conductivity (ohm-cm)1

1 10 100 1000

502.325 456.79 437.8628 422.433

0.101 0.046 0.024 0.025

2.82  108 1.17  107 5.84  107 5.87  106

Fig. 4. Variation of dielectric constant and loss tangent as a function of frequency at room temperature for (a,b) PMN and (c,d) 0.75PMN-0.25PT samples respectively.

Please cite this article as: S. Kashyap, S. C. Bhatt, M. Uniyal et al., Structural and dielectric properties of Lead Magnesium Niobate and Ti-doped Lead Magnesium Niobate at room temperature, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.01.032

4

S. Kashyap et al. / Materials Today: Proceedings xxx (xxxx) xxx

Table 3 The values of dielectric constant, loss tangent and electrical conductivity of 0.75PMN-0.25PT with different frequencies at room temperature. Sample 0.75PMN-0.25PT

Frequency (KHz)

Dielectric Constant (ƐRT)

Loss Tangent (tan d)

Electrical Conductivity (ohm-cm)1

1 10 100 1000

1712 1660 1607 1535

0.023 0.021 0.024 0.034

2.19  108 1.93  107 2.14  106 2.89  105

tric constant with increase in frequency may be due to disturbance in alignment of dipoles with alternating electric field [16]. The variation in dielectric constant, loss tangent and electrical conductivity of PMN and 0.75PMN-0.25PT at different frequencies are tabulated in Tables 2 and 3. Fig. 4 shows the frequency dependent nature of dielectric constant of PMN and 0.75PMN-0.25PT.

Acknowledgements

5. Conclusions

References

The relaxors PMN and 0.75PMN-0.25PT were prepared by solid state reaction method at different sintering and calcination temperature. From the XRD data, it is observed that both samples are in perovskite phase with small amount of pores due to volatile nature of Pb. SEM images show the formation of dens grains with well-defined compact boundaries. The dielectric study of PMN and 0.75PMN-0.25PT shows the frequency dependent nature of dielectric constant, and it is clear from the Tables 2 and 3, that the dielectric constant of PMN can be increased 4 or 5 times at room temperature by the stoichiometric addition of Ti content in PMN.

[1] Y.H. Chen, K. Uchino, M. Shen, D. Viehland, J. Appl. Phys. 90 (3) (2001) 1455– 1458. [2] R. Yimnirun, S. Ananta, E. Meechoowas, S. Wongsaenmai, Phys. D: Appl. Phys. 36 (2003) 1615–1619. [3] T.R. Shrout, J. Fielding Jr., Ultrason. Symp. (1990) 711. [4] G.H. Haertling, J. Am. Ceram. Soc. 82 (1999) 797. [5] R. Zhang, S. Peng, D. Xido, Y. Wang, B. Yang, J. Zhu, P. Yu, W. Zhang, Cryst. Res. Echol. 33 (5) (1998) 827–832. [6] A.J. Moulson, J.M. Herbert, Electroceramics, second ed., Wiley, Chichester, 2003. [7] K. Uchino, Ferroelectric Devices, Marcel Dekker, New York, 2000. [8] J. Huang, N.D. Chateen, J.J. Fitzgerald, Chem. Mater. 10 (1998) 3848–3855. [9] A. Benayad, G. Sebald, B. Guiffard, L. Lebrun, D. Guyomar, E. Pleska, J. Phys. IV Proc. 126 (2005) 53–57. [10] S.W. Choi, T.R. Shrout, S.J. Jang, A.S. Bhalla, Ferroelectrics 100 (1989) 29–38. [11] C. Noblanc, P. Deljurie, Gaucher, G. Calvarin, Silicates Industriels 227–23 (1) (1993) 11–12. [12] J.F. Tressler, T.R. Howarth, Proc 2nd IEEE Int Symp, 2 (2000) 561. [13] H.L.W. Chen, P.K.L. Ng, C.L. Choy, Appl. Phys. Lett. 74 (1999) 3029. [14] W.D. Kingry, Introduction to Ceramics, 2nd ed., Wiley, New York, 1960. [15] S.L. Swartz, T.R. Shrout, Mater. Res. Bull. 17 (1982) 1245–1250. [16] A.N. Tarale, S. Premkumar, V.R. Reddy, Ferroelectrics 516 (2017) 8–17.

Declaration of Competing Interest 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.

Authors are thankful to Dept. of Instrumentation Engineering (USIC), Hemvati Nandan Bahuguna Garhwal University, Srinagar Garhwal, Uttarakhand for availing characterization and dielectric properties measurement facility.

Please cite this article as: S. Kashyap, S. C. Bhatt, M. Uniyal et al., Structural and dielectric properties of Lead Magnesium Niobate and Ti-doped Lead Magnesium Niobate at room temperature, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.01.032