Niobate Complex Perovskite Microwave Dieletric Ceramics Ba(Me_1/3Nb_2/3)O₃ (Me= Zn, Co, Ni and Mg)

Abstract:

Ba(Me1/3Nb2/3)O3 (Me=Zn, Co, Ni and Mg) ceramics were prepared using the conventional mixed oxide route; additives included Al2O3, Ga2O3, SiO2, WO3, B2O3 and V2O5. Powders were mixed, milled for 18h, calcined at 1100°C, remilled pressed into pellets at 100 MPa, sintered in air at temperatures in the range 1350-1550°C and then cooled at 360C h–1 to 5°C h–1. Products were characterised in terms of phase analysis (X-ray diffraction), microstructure (SEM and TEM) and electrical properties (relative permittivity, εr, dielectric Q value and temperature coefficient of resonant frequency,τf). The Q values of the Ba(Me1/3Nb2/3)O3 ceramics depend on the degree of cation ordering and the additives. Slow cooling leads to 1:2 ordering of the B sites and enhanced dielectric Q values. For samples cooled at 5°C h–1 after sintering the Qxf values are in the range 28000 to 98000 GHz, and are in the sequence Ba(Ni1/3Nb2/3)O3, Ba(Co1/3Nb2/3)O3, Ba(Mg1/3Nb2/3)O3 and Ba(Zn1/3Nb2/3)O3. Additions of BaO-4WO3 or V2O5 yield higher Qxf values than Al2O3. Highly ordered Ba(Zn1/3Nb2/3)O3 has a relative permittivity of 39.4, but most other Ba(Me1/3Nb2/3)O3 ceramics exhibit εr of 31-32. The temperature coefficient of resonant frequency, τf, varies from –18 ppm/°C (Ba(Ni1/3Nb2/3)O3) to +32 ppm/°C (Ba(Mg1/3Nb2/3)O3); the sintering additives (Al2O3 and BaO-4WO3) change τf by typically 10-16 ppm/°C.

• Periodical: Advances in Science and Technology (Volume 45)
• Pages: 2323-2331
• DOI: https://doi.org/10.4028/www.scientific.net/AST.45.2323
• Online since: October 2006
• Authors: F. Azough, Colin Leach, Robert Freer
• Keywords: Complex Perovskite, Microwave Dielectric, Niobates, Stoichiometry

References

[1] J. I Yang, S. Nahm, C.H. Choi, H. J Lee, J.C. Kim, and H.M. Park; Jpn. J. Appl. Phys. Vol. 41 (2002) p.702.

[2] J.I. Yang, S. Nahm, C.H. Choi, H.J. Lee, J.C. Kim, and H.M. Park, H. M; J. Am. Ceram. Soc. Vol. 85 (2002) p.165.

[3] S. Kavashima, M. Nishida, I. Ueda and H. Ouchi; J. Am. Ceram. Soc. Vol. 66 (1983) p.421.

[4] M.A. Akbas and P.K. Davis; J. Am. Ceram. Soc. Vol. 81 (1998) p.670.

[5] I.T. Kim and Y. H Kim; J. Mater. Res. Vol. 12 (1997) p.518.

[6] K. Endo, K. Fujimoto and K. Murakawa; J. Am. Ceram. Soc. Vol 70 (1987) p. C215 7. S.Y. Cho, H.J. Youn K.S. and Hong; J. Mater. Res. Vol. 12 (1997) p.1558.

[8] K.H. Yoon, B.J. Jung and E.S. Kim; J. Mater. Sci. Lett. Vol. 8 (1989) p.819.

[9] I. Molodetsky and P.K. Davis; J. Euro. Ceram. Soc. Vol. 21 (2001) p.2587.

[10] B.W. Hakki and P.D. Coleman; IEEE Trans. Mirowave Theory Theo. Vol MTT-18 (1980) p.402.

[11] K.H. Yoon, S.J. Yoo, W.S. Kim, J.B. Kim and E.S. Kim; Jpn. J. Appl. Phys. Vol 38 (1990) p.5616.

[12] R.D. Shannon, J. Appl. Phys. Vol. 73 (1003), p.348.