Sains Malaysiana 43(6)(2014): 833–842

Characteristics of Nanostructured Ca_xZn_(1-x)Al₂O₄ Thin Films Prepared by Sol-Gel Method

for GPS Patch Antennas

(Ciri Filem Nipis Ca_xZn(_1-x)Al₂O₄ Berstruktur Nano yang Dihasilkan Melalui Kaedah

Sol-Gel untuk GPS Tampalan Antena)

WAN NASARUDIN WAN JALAL¹, HUDA ABDULLAH^1*, MOHD SYAFIQ ZULFAKAR¹, SAHBUDIN SHAARI², MOHAMMAD THARIQUL ISLAM³& BADARIAH BAIS¹

¹Department of Electrical, Electronic and System Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia

²Institute of Microengineering and Nanoelectronics (IMEN), Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia

³The Institute of Space Science (ANGKASA), Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia

Diserahkan: 28 Mac 2013/Diterima: 2 Februari 2014

ABSTRACT

CaxZn(1-x)Al2O4 thin films (x = 0.00; 0.05; 0.10; 0.15 and 0.20) were prepared by sol-gel method with the substitution of Zn²⁺ by Ca²⁺ in the framework of _ZnAl2O4. The effect of Ca addition on the structure and morphology of CaZnAl₂O₄ thin films was investigated by x-ray diffraction (XRD), field-emission scanning electron microscope (FESEM), energy-dispersive x-ray spectroscopy (EDX), ultra-violet visible (UV-Vis) and atomic force microscope (AFM). The XRD patterns showed the characteristic peaks of face-centred cubic (fcc) ZnAl₂O₄ and CaZnAl₂O₄. The addition of Ca increased the crystallite size from 8.9 to 30.2 nm. The bandgap of Ca_xZn_(1-x)Al₂O₄ thin film was found in the range of 3.40 to 3.84 eV. SEM micrograph shows the morphology of all thin films is sphere-like, with the grain size increased from 33 to 123 nm. The AFM images show the roughness of surface morphology increased. The substitution of Zn²⁺ by Ca2+ increased the crystallite size, grain size and surface roughness which evidently increased the density (4.59 to 4.64 g/cm³) and dielectric constant (8.48 to 9.54). The composition of

CaxZn_(1-x)Al₂O₄ is considered as suitable material for GPS patch antennas.

 Keywords: Band gap; Ca-ZnAl2O4; GPS patch antena; nanostructures

ABSTRAK

Filem nipis CaxZn(1-x)Al2O4(x = 0.00; 0.05; 0.10; 0.15 dan 0.20) telah dihasilkan dengan kaedah sol-gel iaitu menggantikan Zn2+ dengan Ca2+ di dalam bahan utama ZnAl2O4. Kesan terhadap penambahan Ca pada struktur dan morfologi filem nipis CaZnAl2O4 telah dianalisis dengan menggunakan pembelauan sinar-x (XRD), mikroskopi imbasan pancaran medan elektron (FESEM), x-ray serakan tenaga spektroskopi (EDX), cahaya nampak ultra lembayung (UV-Vis) dan mikroskopi daya atomik (AFM). Corak pembelauan XRD menunjukkan ciri-ciri puncak berpusat muka padu pada bahan ZnAl₂O₄ dan CaZnAl₂O₄. Penambahan Ca telah meningkatkan saiz kristal daripada 8.9 kepada 30.2 nm. Jalur tenaga bagi filem nipis Ca_xZn_(1-x)Al₂O₄ ialah antara 3.40 hingga 3.84 eV. Graf mikro SEM menunjukkan morfologi bagi kesemua filem nipis adalah berbentuk butiran dengan saiz butiran meningkat daripada 33 kepada 123 nm. Imej AFM menunjukkan berlakunya peningkatan pada permukaan morfologi Ca_xZn_(1-x)Al₂O₄. Penggantian Zn²⁺ dengan Ca²⁺ telah meningkatkan saiz butiran dan peningkatan kekasaran permukaan yang seterusnya memberi kesan terhadap ketumpatan bahan (4.59 kepada 4.64 g/cm³) dan pemalar dielektrik (8.48 kepada 9.54). Komposisi Ca_xZn_(1-x)Al₂O₄ dianggap sebagai bahan yang sesuai untuk penghasilan GPS tampalan antena.

Kata kunci: Ca-ZnAl₂O₄; GPS tampalan antena; jalurtenaga; strukturnano

RUJUKAN

Barros, B.S., Melo, P.S., Kiminami, R.H.G.A., Costa, A.C.F.M., de Sa, G.F. & Alves Jr. S. 2006. Photophysical properties of Eu³⁺ and Tb³⁺-doped ZnAl₂O₄ phosphors obtained by combustion reaction. Journal of Material Science 41: 4744-4748.

Bian, J.J., Yan, K. & Dong, Y.F. 2008. Microwave dielectric properties of A1-3x/2 La x (Mg ½) 0 3 (A = Ba, Sr, Ca; 0.0 < 0.05) double perovskites. Materials Science and Engineering B – advanced Functional Solid-State Materials 147(1): 27-34.

Chatpong Bangbai, Krisana Chongsri, Wisanu Pecharapa & Wicharn Techitdheera. 2013. Effect of Al and N doping on structural and optical properties of sol-gel derived ZnO thin films. Sains Malaysiana 42: 239-246.

Chen, Y-C. 2011. Microwave dielectric properties of (Mg_(1−x) Cox)₂SnO₄ ceramics for application in dual-band inverted-e-shaped monopole antenna. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 58: 2531-2538.

Ciupina, V., Carazeanua, I. & Prodan, G. 2004. Characterization of ZnAl₂O₄ nanocrystals prepared by coprecipitation and microemulsion techniques. Journal of Optoelectronics and Advanced Materials 6: 1317-1322.

de Souza, L.K.C., Zamian, J.R., da Rocha Filho, G.N., Soledad, L.E.B., dos Santos, I.M.G., Souza, A.G., Scheller, T., Angelica, R.S. & da Costa, C.E.F. 2009. Blue pigments based on CoxZn1-xAl₂O₄ spinels synthesized by the polymeric precursor method. Dyes and Pigments 81: 187-192.

Farley, N.R.S., Staddon, C.R., Zhao, L.X., Edmonds, K.W., Gallagher, B.L. & Gregory, D.H. 2003. New sol-gel synthesis of ordered nanostructured doped ZnO films. J. App. Phys. 93: 1-8.

Fatemeh Davara & Masoud Salavati-Niasaria. 2011. Synthesis and characterization of spinel- type zinc aluminate nanoparticles by a modified sol-gel method using new precursor. Journal of Alloys and Compounds 509: 2487-2492.

Fauzana, A.N., Azmi, B.Z., Sabri, M.G.M., Wan Abdullah, W.R. & Hashim, M. 2013. Microstructural and nonlinear electrical properties of ZnO ceramics with small amount of MnO₂ dopant. Sains Malaysiana 42: 1139-1144.

Huang, C-L., Chen, J-Y. & Li, B-J. 2009. Characterization and dielectric behavior of a new dielectric ceramics Ca(Mg1/3Nb2/3)O3–(Ca_0.8Sr_0.2)TiO₃ at microwave frequencies. J. of Alloys and Compounds 484: 494-497.

Huang, C-L., Chen, J-Y. & Wang, Y-H. 2009. Microwave dielectric properties of (Mg_0.95Co_0.05)TiO₃-(Na0.5Nd0.5) TiO₃ ceramic system. J. of Alloys and Compounds 478: 842-846.

Huang, C-L., Yang, T-J. & Huang, C-C. 2009. Low dielectric l oss c eramics in the ZnAl₂O₄–TiO₂ s ystem as a τf compensator. J. of the American Ceramic Society 92: 119-124.

Hui Zhang, Liang, Fang, Elsebrock, R. & Yuan, R.Z. 2005. Crystal structure and microwave dielectric properties of a new A₆B₅O₁₈-type cation-deficient perovskite Ba₃La₃Ti₄NbO₁₈. Materials Chemistry and Physics 93: 450-454.

Ianos, R., Lazau, R., Lazau, I. & Pacurariu, C. 2011. Chemical oxidation of residual carbon from ZnAl₂O₄ powders prepared by combustion synthesis. 2012. J. of the European Ceramic Society 32: 1605-1611.

Kingery, W., Bowen, H. & Uhlmann, D. 1976. Introduction to Ceramics. John Willey & Son, New York.

Koops, C.G. 1951. On the dispersion of resistivity and dielectric constant of some semiconductors at audio frequencies. Physics Review 81: 121-124.

Lei, W., Lu, W-Z., Wang, X-H., Liang, F. & Wang, J. 2011. Phase composition and microwave dielectric properties of ZnAl₂O₄-Co₂TiO₄ low-permittivity ceramics with high quality factor. J. of the American Ceramic Society 94: 20-23.

Lei, W., Lu, W-Z., Liu, D. & Zhu, J-H. 2009. Phase evolution and microwave dielectric properties of (1-x)ZnAl₂O_4-x Mg₂TiO₄ ceramics. Journal of the American Ceramic Society 92: 105-109.

Muhammad E. Abdul Jamal, Sakthi Kumar D. & Anantharaman, M.R. 2011. On structural, optical and dielectric properties of z inc a luminate nanoparticles. Bull. Mater. Sci.34: 251-259.

Narang, S.B. & Shalini, B. 2010. Low loss dielectric ceramics for microwave applications: A review. Journal of Ceramic Processing Research 11: 316-321.

Nikumbh, A.K. & Adhyapak, P.V. 2010. Synthesis, properties and optimization of the rheologicalbehaviors on alumina and zinc aluminate powders obtain from dicarboxylate precursors. Powder Technology 202: 14-23.

Renata, F.M. & Osvaldo, A.S. 2010. Thin f ilm of ZnAl₂O₄: Eu³⁺ synthesized by a non-alkoxide precursor sol-gel method. Journal of Brazil Chemistry Society 21: 1395-1398.

Rodríguez, M.A., Aguilar, C.L. & Aghayan, M.A. 2012. Solution combustion synthesis and sintering behavior of CaAl₂O₄. Ceramics International 38: 395-399.

Saberi, A., Golestani-Fard, F., Sarpoolaky, H., Willert-Porada, M., Gerdes, T. & Simon, R. 2008. Chemical synthesis of nanocrystalline magnesium aluminate spinel via nitrate-citrate combustion route. Journal of Alloy Compound 462: 142-146.

Sanchez, R.D., Saleta, M.E., Shapoval, O., Gehrke, K., Moshnyaga, V. & Samwer, K. 2010. Characterization of geometrically frustrated Zn_1-xMnxAl₂O₄ thin films prepared by metalorganic aerosol deposition. Journal of Physics: Conference Series 200: 1-4.

Sebastian, M.T. 2008. Dielectric Materials for Wireless Communication. Jordan Hill, Oxford, UK: Elsevier Ltd.

Subramanian, M.A., Shannon, R.D., Chai, B.H.T., Abraham, M.M. & Wintersgill, M.C. 1989. Dielectric constants of BeO, MgO, and CaO using the two-terminal method. Phys. Chem. Minerals 16: 741-746.

Surendran, K.P., Santha, N., Mohanan, P. & Sebastian, M.T. 2004. Temperature stable low loss ceramic dielectrics in (1-x) ZnAl₂O_4-xTiO₂ system for microwave substrate applications. The European Physical Journal B 41: 301-306.

Suresh K Sampath, D.G. Kanhere & Ravindra Pandey. 1999. Electronic structure of spinel oxides: Zinc aluminate and zinc gallate. J. Phys. Condens. Matter 11: 3635-3644.

Tawatchai Charinpanitkul, Pattama Poommarin, Akkarat Wongkaew & Kim, K-S. 2009. Dependence of zinc aluminate microscopic structure on its synthesis. Journal of Industrial and Engineering Chemistry 15: 163-166.

Thinesh Kumar, R., Clament Sagaya Selvam, N., Ragupathi, C., John Kennedy, L. & Judith Vijaya, J. 2012. Synthesis, characterization and performance of porous Sr(II)-added ZnAl₂O₄ nanomaterials for optical and catalytic applications. Powder Technology 224: 147-154.

Tian, X., Wan, L., Pan, K., Tian, C., Fu, H. & Shi, K. 2009. Facile synthesis of mesoporous ZnAl₂O₄ thin films through the evaporation-induced self-assembly method. Journal of Alloys and Compounds 488(1): 320-324.

Wagner, K.W. 1913. Zur theorie der unvollkommenen dielektrika. Annalen der Physik 345: 817-855.

Wang, X.C., Lei, W. & Lu, W.Z. 2009. Novel ZnAI₂0₄-based microwave dielectric ceramics with machinable property and its application for GPS antenna. Ferroelectrics 388: 80-87.

Wood, D.L. & Tauc, J. 1972. Weak absorption tails in amorphous semiconductors. Phys. Rev. B 5: 3144-3151.

Wu, J-M., Lu, W-Z., Lei, W. & Wang, X-C. 2011. Preparation of ZnAl2O4-based microwave dielectric ceramics and GPS antenna by aqueous gelcasting. Materials Research Bulletin 46: 1485-1489.

Xavier, C.S., Sczancoski, J.C., Cavalcante, L.S., Paiva- Santos, C.O., Varela, J.A., Longo, E. & Li, M.S. 2009. A new processing method of CaZn₂(OH)_6.2H₂O powders: Photoluminescence and growth mechanism. Solid State Sciences 11: 2173-2179.

Ye, X., Wen, W.L. & Lu, W-Z. 2009. Microwave dielectric characteristics of Nb₂O₅-added 0.9Al₂O_3–0.1TiO₂ ceramics. Ceramics International 35: 2131-2134.

Zawadzki, M., Staszak, W., López-Suárez, F.E., Illán-Gómez, M.J. & Bueno-López, A. 2009. Preparation, characterisation and catalytic performance for soot oxidation of copper-containing ZnAl₂O₄ spinels. Applied Catalysis A: General 371: 92-98.

Zhang, D., Wang, C., Liu, Y., Shi, Q., Wang, W. & Zhai, Y. 2012. Green and red photoluminescence from ZnAl₂O₄: Mn phosphors prepared by sol-gel method. Journal of Luminescence 132: 1529-1531.

*Pengarang untuk surat-menyurat; email: huda@vlsi.eng.ukm.edu.my