Medium Effect on Permittivity of BaTiO3 by Solid State Reaction   Hatice Z. AKBAS a*, Ferhat GUDERb, Zeki AYDINc, Selvin USTABASd a* :Department of Physics, Faculty of Arts and Science, Mustafa Kemal University, Hatay b :Jale Tezer Education Institutions, Ankara c :Department of Chemistry, Faculty of Science and Arts, Mustafa Kemal University, Hatay d :MARGEM, Mustafa Kemal University, Hatay

INTRODUCTION Solid state reaction method is commonly used method for the preparation of BaTiO3 ceramics from a mixture of BaCO3 and TiO2 powders because it is easy, cheap and suitable for mass production, which is important for many industrial applications. The solid state reaction method could be summarized: BaCO3 and TiO2 powders are mixed by shaker, ball milling etc. In this process, some liquid like acetone, alcohol, water can be added to the mixture to homogenize thoroughly. BaCO3 and TiO2 powders do not react together at room temperature so the mixture is calcined about 1000 °C in order for the reaction. After calcination, the powder are pressed into pellets and the pellets sintered to investigate (di)electric or ferroelectric properties. World Conference on Technology, Innovation and Entrepreneurship,ISTANBUL May 28-30, 2015

Homogenization conditions [Petrović, 2013], Rate of solid state reaction and phases in the powders was very sensitive to the reactants and the synthesis conditions. Homogenization conditions [Petrović, 2013], Calcination conditions [Manzoor, 2007; Felgner, 2004] and Sinterization conditions [Zhong, 1994] were already been studied. Petrović, M. M. V. Et al., J Sol-Gel Sci Technol. 67, 267–272 (2013). Manzoor, U. & Kim, D.K, J. Mater. Sci. Technol., 23 (5), 655-658 (2007). Felgner K.-H.et al., Materials Letters, 58 (12–13) 1943–1947, (2004) Zhong, W. Et al., Ferroelectrics, 160, 55-59 (1994) May 28-30, 2015 World Conference on Technology, Innovation and Entrepreneurship,ISTANBUL

Relative volume fraction of the cubic and tetragonal phases in the powders prepared by hydro-thermal techniques was found that very sensitive to the synthesis condition [Moon, 2006]. Yoon et al.[2007] and Stawski et al. [2010] reported that particle sizes of powders prepared by hydro-thermal techniques increase with increasing water and crystal structure of particle change from tetragonal to cubic. These studies showed that reaction medium was an important factor that controlled structural and morphological properties like rate of crystallization, phase and the crystallite size of the powders Moon S.-M. et al., Journal of Electroceramics, 17 (2-4), 841-845 (2006) Yoon S. et al., Journal of the American Ceramic Society, 90 (1), 311–314, (2007) Stawski T. M. Et al., Journal of the American Ceramic Society, 93 (10) 3443–3448, (2010) May 28-30, 2015 World Conference on Technology, Innovation and Entrepreneurship,ISTANBUL

AIM Homogenization medium effect of BaTiO3 produced by solid state reaction method has not been investigated up to now. In this study, BaTiO3 powders were produced in de-ionized water, methanol and acetone. Influence of the homogenization medium on structural, morphological and dielectric properties of BaTiO3 ceramics by solid state reaction was investigated. May 28-30, 2015 World Conference on Technology, Innovation and Entrepreneurship,ISTANBUL

EXPERIMENTAL BaTiO3-based ceramics were prepared by solid-state process. May 28-30, 2015 World Conference on Technology, Innovation and Entrepreneurship,ISTANBUL

Water, Methanol, Acetone TiO2 powder BaCO3 powder Medium with zirconia balls STEP 1: Materials BaCO3 and TiO2 powders used analytical grade with purity better than 99 %. Powders were mixed inside polyethylene sample vials with 5 mm diameter zirconium balls in different medias (de-ionized water, methanol and acetone) Shaker Mixer Compact STEP 2: Homogenization The vials are shaken simultaneously by Compact Mixer Shaker (Edmund Bühler, Germany ) at 200 rpm with motion orbital for 18 hours to homogenize and to de-agglomerate the powders May 28-30, 2015 World Conference on Technology, Innovation and Entrepreneurship,ISTANBUL

Dried STEP 3: Dried All muddy mixtures were dried at 120 °C for about 1 hour at the same time. BaCO3 TiO2 BaTiO3 STEP 4: Calcination The powders were calcined at 1100 °C for 4 hours in alumina crucibles all together. May 28-30, 2015 World Conference on Technology, Innovation and Entrepreneurship,ISTANBUL

The structure of powders were confirmed by X-ray diffraction (XRD). World Conference on Technology, Innovation and Entrepreneurship,ISTANBUL May 28-30, 2015

Sintered at 1300 °C for 2 hours Pressed at 235 MPa by computer-controlled press machine into disc shaped pellets Sintered at 1300 °C for 2 hours to get dense ceramic May 28-30, 2015 World Conference on Technology, Innovation and Entrepreneurship,ISTANBUL

Raman Spectroscopy was used to verify sintered BaTiO3 pellets. SEM images were used to analyze the morphology of sintered pellets. The complex impedance measurements of samples were carried out using dielectric spectrometer. Complex permittivity and resistivity of ceramics were studied in a wide frequency range of 100 μHz- 20 MHz at room temperature. World Conference on Technology, Innovation and Entrepreneurship,ISTANBUL May 28-30, 2015

RESULTS AND DISCUSSION May 28-30, 2015 World Conference on Technology, Innovation and Entrepreneurship,ISTANBUL

X-ray diffraction patterns of BaTiO3 powders were calcined at 1100 °C for 4 h. The predominant XRD peaks of; BaTiO3: 2 =22°, 32°, 38° , 45°, 55° and 65° at ICSD card number: 01-075-0215 BaCO3 :2=10°-30° [Antao, 2007] TiO2 : 2 =28°, 36°, 42° and 55° [Thamaphat, 2008] World Conference on Technology, Innovation and Entrepreneurship,ISTANBUL May 28-30, 2015 13

Raman spectra of BaTiO3 pellets were sintered at 1300 °C for 2 h. Raman active modes of BaTiO3 pellets are 715 cm-1, 512 cm-1, 305 cm-1, 261 cm-1, 162 cm-1 and 118 cm-1. Around 310 cm-1 peak is a peak for tetragonal BaTiO3 [Qi, 2011]. There are no sign of Raman peaks for BaCO3 (1059 cm-1 and 694 cm-1) [Pasierb, 2001] and TiO2 (143 cm-1) [Choi, 2005]. World Conference on Technology, Innovation and Entrepreneurship,ISTANBUL May 28-30, 2015 14

Scanning electron microscopy (SEM) images of sintered samples X 200 X 1000 X 2000 d) Methanol e) Methanol f) Methanol g) Acetone h) Acetone i) Acetone a) Distilled water b) Distilled water c) Distilled water World Conference on Technology, Innovation and Entrepreneurship,ISTANBUL May 28-30, 2015

Reel part of complex permittivity of sintered pellets World Conference on Technology, Innovation and Entrepreneurship,ISTANBUL May 28-30, 2015

Imaginary part of complex permittivity of sintered pellets World Conference on Technology, Innovation and Entrepreneurship,ISTANBUL May 28-30, 2015

Resistivity of sintered pellets World Conference on Technology, Innovation and Entrepreneurship,ISTANBUL May 28-30, 2015

CONCLUSION May 28-30, 2015 World Conference on Technology, Innovation and Entrepreneurship,ISTANBUL

DIELECTRIC POLARIZATION MECHANISMS Dipolar and space charge polarizations contribute to dielectric constant dominantly at lower frequency. May 28-30, 2015 World Conference on Technology, Innovation and Entrepreneurship,ISTANBUL

CONDUCTION AND FAILURE MECHANISMS IN BaTiO3 (Rawal) The intrinsic type imperfections : various electronic disorders, dislocations, grain boundaries …. This cause a sudden current which results in an immediate breakdown The extrinsic type imperfections: porosity, cracks, local contamination This generate a leakage current which leads to (self) heating Rawal, B. S., & Chan, N. H. InProceedings of the 34th Electronic Components Conference, New Orleans,184-188 (1984,). May 28-30, 2015 World Conference on Technology, Innovation and Entrepreneurship,ISTANBUL

CONDUCTION AND FAILURE EFFECT IN MEDIUM Ba and Ti could be hydrolyzed [Stawski, 2010] different proportion in different mediums. Ion incorporation in the lattice could be different for samples homogenized in water (H2O), methanol (CH4O) and acetone (C3H6O). It could be changed structural properties of synthesized BaTiO3 [Yoon, 2007]. Disproportionation of the medium solution: H2O+H2OH3O++OH- Water CH2OH+CH2OH  CH3OH-+CH2O- Methanol C3H6O  None Acetone The hydroxyl ions in BaTiO3 [Yoon, 2007; Stawski, 2010] and structural properties of samples homogenized in water, methanol and acetone can be changed dielectric properties of the ceramics. Yoon S. et al., Journal of the American Ceramic Society, 90 (1), 311–314, (2007) Stawski T. M. et al., Journal of the American Ceramic Society, 93 (10) 3443–3448, (2010) May 28-30, 2015 World Conference on Technology, Innovation and Entrepreneurship,ISTANBUL

CONCLUSION Using water in the homogenization process keeps the grains together while the acetone separated them. There is a clear correlation between particle size and homogenization medium. The pellets homogenized in different medium have different grain sizes, and cavities between grain walls. The complex permittivity and complex AC conductivity of samples by solid state reaction processes strongly depends on grain sizes [Zhong, 1994], and cavities between grain walls. May 28-30, 2015 World Conference on Technology, Innovation and Entrepreneurship,ISTANBUL

THANK YOU FOR YOUR ATTENTION ANY QUESTION Acknowledgement The authors thank to Scientific Research Projects Coordination Unit for project founding by grant no: 326, Mustafa Kemal University, Hatay. May 28-30, 2015 World Conference on Technology, Innovation and Entrepreneurship,ISTANBUL

St. Pierre Church is in city of Hatay (Antakya or Anṭiokia), TURKEY. It is considered the world's first cave church. UNESCO submitted it one of the World Heritage at 2011 World Conference on Technology, Innovation and Entrepreneurship,ISTANBUL May 28-30, 2015 25