Effects of NiO nanoparticles on the magnetic properties and diffuse phase transition of BZT/NiO composites
© Jarupoom et al; licensee Springer. 2012
Received: 10 September 2011
Accepted: 5 January 2012
Published: 5 January 2012
A new composite system, Ba(Zr0.07Ti0.93)O3 (BZT93) ceramic/NiO nanoparticles, was fabricated to investigate the effect of NiO nanoparticles on the properties of these composites. M-H hysteresis loops showed an improvement in the magnetic behavior for higher NiO content samples plus modified ferroelectric properties. However, the 1 vol.% samples showed the optimum ferroelectric and ferromagnetic properties. Examination of the dielectric spectra showed that the NiO additive promoted a diffuse phase transition, and the two phase transition temperatures, as observed for BZT93, merged into a single phase transition temperature for the composite samples.
Keywordsceramics composites magnetic properties electrical properties microstructure
Ferroelectric materials are widely used in a broad range of applications, especially in the design of electronic devices such as non-volatile memory, capacitors, transducers, actuators, etc. [1, 2]. Barium zirconate titanate (Ba(ZrxTi1-x)O3) [BZT] is one such interesting ferroelectric material due to its high relative permittivity, which makes it a very attractive material for use in capacitor applications such as boundary layer capacitors and multilayer ceramic capacitors [3–6]. Furthermore, BZT for some compositions exhibits high ferroelectric and piezoelectric properties. Due to the environmental concern, this material is also beneficial since it is a lead-free material.
Recently, much attention has been paid to multiferroic materials because of the coexistence of ferromagnetic and ferroelectric ordering at room temperature. However, multiferroic materials which exhibit both high ferromagnetic and ferroelectric properties are very rare. This is because ferromagnetic materials need transition metals with unpaired 3d electrons and unfilled 3d orbitals, while ferroelectric polarization requires transition metals with filled 3d orbitals . An alternative way to obtain high ferromagnetic and magnetic properties is to produce composite materials which contain combined ferroelectric and magnetic phases. These materials are called multiferroic composites, and many authors have fabricated and reported the properties of multiferroic composites . In this work, a new system of multiferroic composites was fabricated. The BZT in the composition of Ba(Zr0.07Ti0.93)O3 (BZT93) was synthesized and used as matrix for the composites. NiO nanopowder with a particle size of approximately 100 nm was added to BZT93, and the mixed materials were sintered at various sintering temperatures to form the composites. Properties of the composites were then determined and reported.
The composites were prepared by a conventional mixed-oxide method. BZT powder was prepared based on the stoichiometric formula Ba(Zr0.07Ti0.93)O3. The raw metal oxide, BaCO3, TiO2, and ZrO2 were mixed and calcined at 1,200°C for 2 h. Different volume ratios (0, 1, 2, and 3 vol.%) of the NiO nanoparticles (Sigma-Aldrich Corporation, St. Louis, MO, USA; with a particle size of < 100 nm) were mixed with the BZT93 powder and then milled for 24 h. The ball-milled powders were pressed into a disk shape and then sintered at temperatures ranging from 1,250°C to 1,450°C for 2 h. The densities of all the disks were determined after sintering using the Archimedes method. Phase formation of the sintered ceramics was investigated by X-ray diffraction [XRD] technique. The magnetic properties were measured using a vibrating sample magnetometer of the Lake Shore Model 7404 (Lake Shore Cryotronics, Inc., Westerville, OH, USA). The ferroelectric properties were performed using a Sawyer-Tower circuit. Relative permittivity and tangent loss were measured as a function of temperature using an LCR meter.
Results and discussion
Densification and phase formation
Magnetic and ferroelectric properties
Unit cell volume, magnetic, and ferroelectric properties of BZT93/NiO composites
Unit cell volume
Dielectric properties and phase transition
The value of δ γ was determined from a plot of ln (εr, max/ε r ) versus the (T - Tm)2. The values of δ γ as a function of NiO content are shown in Table 1. The parameter δ γ increased with increasing NiO content, confirming that the addition of NiO promoted the diffuse phase transition of the composites.
Huang and Tuan proposed that Ni ions could substitute the Ti ions in BaTiO3 lattices . It has also been reported that La3+ doped at the Ti site of BaTiO3 ceramics exhibits a change in the transition temperature as well as a pronounced diffuseness transition [18–22]. The La ions are effective in breaking the long-range order and produce Ti vacancies. This breakage of long-range ordering leads to a reduction of the ferroelectric characteristics and enhances the diffuse phase transition. In our present work, unit cell volume was calculated from XRD diffraction patterns, and the calculation result is listed in Table 1. The calculation result indicated an increase in the unit cell volume after adding NiO. This increase may be due to the Ni ions substituting the Ti ions (at the B site). Therefore, substitution of the Ni ions at the B site may result in breaking the long-range ordering, resulting in a reduction of the ferroelectric behavior with the transition becoming more diffuse . Further, with increasing NiO content, the structure of the composites became more heterogeneous. This may contribute to the diffuse phase transition of the samples. From Figure 4, the increase of loss tangent with NiO content implies a higher electrical conductivity of the composites. However, the highest loss tangent in the present work was lower than 0.035, indicating that the present composites still have a potential for capacitor applications. This result also supports the reason for the presence of the lossy capacitor hysteresis behavior of the composites.
In this work, the properties of BZT93/NiO composites were determined for the first time. X-ray diffraction results revealed the presence of NiO particles in the composites. The additive of NiO nanoparticles enhanced the magnetic behavior. The increase of loss tangent affected the ferroelectric hysteresis where a lossy capacitor hysteresis loop was clearly observed for the sample containing high amounts of NiO. However, the 1.0 vol.% samples showed the optimum magnetic/ferroelectric behavior. In addition, the additive also promoted the dielectric diffuse phase transition behavior while loss tangent values were still low. These characteristics of the composites may make them have potential for many electronic applications in the future.
This work was supported by the Faculty of Science, Chiang Mai University and the Office of Higher Education Commission (OHEC).
- Bhalla AS, Guo R, Roy R: The perovskite structure- a review of its role in ceramic science and technology. Mat Res Innovat 2000, 4: 3–26. 10.1007/s100190000062View Article
- Yu Z, Guo R, Bhalla AS: Dielectric behavior of Ba(Ti1-xZrx)O3single crystals. J Appl Phys 2000, 88: 410–415. 10.1063/1.373674View Article
- Yang GY, Dickey EC, Randall CA, Barber DE, Pinceloup P, Henderson MA: Oxygen nonstoichiometry and dielectric evolution of BaTiO3. Part I-improvement of insulation resistance with reoxidation. J Appl Phys 2004, 96: 7492–7499. 10.1063/1.1809267View Article
- Yang GY, Dickey EC, Randall CA, Barber DE, Pinceloup P, Henderson MA: Oxygen nonstoichiometry and dielectric evolution of BaTiO3. Part II-insulation resistance degradation under applied dc bias. J Appl Phys 2004, 96: 7500–7508. 10.1063/1.1809268View Article
- Chazono H, Kishi H: DC-electrical degradation of the BT-based material for multilayer ceramic capacitor with Ni internal electrode: impedance analysis and microstructure. Jpn J Appl Phys 2001, 40: 5624–5629. 10.1143/JJAP.40.5624View Article
- Kishi H, Mizuno Y, Chazono H: Base-metal electrode-multilayer ceramic capacitors: past, present and future perspectives. Jpn J Appl Phys 2003, 42: 1–15. 10.1143/JJAP.42.1View Article
- Hwang HJ, Watari K, Sando M, Toriyama M, Nihara K: Low-temperature sintering and high-strength Pb(Zr, Ti)O3-matrix composites incorporating silver particles. J Am Ceram Soc 1997, 80: 791–793.View Article
- Ederer C, Spaldin NA: Recent progress in first-principles studies of magnetoelectric multiferroics. Solid State Mater Sci 2005, 9: 128–139. 10.1016/j.cossms.2006.03.001View Article
- Jarupoom P, Pengpat K, Rujijanagul G: Enhanced piezoelectric properties and lowered sintering temperature of Ba(Zr0.07Ti0.93)O3by B2O3addition. Curr Appl Phys 2010, 10: 557–560. 10.1016/j.cap.2009.07.020View Article
- Yu Z, Ang C, Guo R, Bhalla AS: Piezoelectric and strain properties of Ba(Ti1-xZr x )O3ceramics. J Appl Phys 2002, 92: 1489–1493. 10.1063/1.1487435View Article
- Das SR, Choudhary RN, Bhattacharya P, Katiyar RS, Dutta P, Manivannan A, Seehra MS: Structural and multiferroic properties of La-modified BiFeO3ceramics. J Appl Phys 2007, 101: 034104–034111. 10.1063/1.2432869View Article
- Chi ZH, Yang H, Feng SM, Li FY, Yu RC, Jin CQ: Room-temperature ferroelectric polarization in multiferroic BiMnO3. J Mag Mag Mater 2007, 310: e358-e360. 10.1016/j.jmmm.2006.10.335View Article
- Kumar MM, Srinath S, Kumar GS, Suryanarayana SV: Spontaneous magnetic moment in BiFeO3-BaTiO3solid solutions at low temperatures. J Magn Magn Mater 1998, 188: 203–212. 10.1016/S0304-8853(98)00167-XView Article
- Chen J, Qi Y, Shi G, Yan X, Yu S, Cheng J: Diffused phase transition and multiferroic properties of 0.57 (Bi1-xLax)FeO3-0.43PbTiO3crystalline solutions. J App Phys 2008, 104: 064124–064128. 10.1063/1.2986497View Article
- Jarupoom P: Electrical property development of lead-free barium zirconate titanate ceramics. In Ph.D Thesis. Chiang Mai University; 2011.
- Makovec D, Samardzija Z, Drofenik M: Solid solubility of holmium, yttrium, and dysprosium in BaTiO3. J Am Ceram Soc 2004, 87: 1324–1329. 10.1111/j.1151-2916.2004.tb07729.xView Article
- Huang YC, Tuan WH: Exaggerated grain growth in Ni-doped BaTiO3ceramics. Mat Chem Phys 2007, 105: 320–324. 10.1016/j.matchemphys.2007.04.075View Article
- Tang XG, Chew KH, Chan HLW: Diffuse phase transition and dielectric tunability of Ba(Zr y Ti1-y)O3relaxor ferroelectric ceramics. Acta Mater 2004, 52: 5177–5183. 10.1016/j.actamat.2004.07.028View Article
- Tuan WH, Huang YC: High percolative BaTiO3-Ni nanocomposites. Mat Chem Phys 2009, 118: 187–190. 10.1016/j.matchemphys.2009.07.029View Article
- Morrison FD, Sinclair DC, Skakle JMS, West AR: Novel doping mechanism for very-high-permittivity barium titanate ceramics. J Am Ceram Soc 1998, 81: 1957–1960.View Article
- Morrison FD, Sinclair DC, West AR: An alternative explanation for the origin of the resistivity anomaly in La-doped BaTiO3. J Am Ceram Soc 2001, 84: 474–476.View Article
- Morrison FD, Sinclair DC, West AR: Electrical and structural characteristics of lanthanum-doped barium titanate ceramics. J App Phys Soc 1999, 86: 6355–6366. 10.1063/1.371698View Article
- Gulwade D, Gopalan P: Study of diffuse phase transition in BaTiO3-LaAlO3. J Alloys Compd 2009, 481: 316–319. 10.1016/j.jallcom.2009.02.141View Article
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.