Dielectric resonator (DR) is a piece of dielectric material with high dielectric constant and high Q factor (> 3000) which is used as resonators and filters in communication devices. Due to its high dielectric constant, the size of the resonator gets reduced compared to the conventional transmission line based resonators. The DRs are expected to have a near zero temperature coefficient of resonant frequency (f). Among the dielectric materials that can be used as a DR, in the family of columbites, ZnNb2O6 is one of the choices since it has a dielectric constant around 21 and Q×f is of the order of 80,000. Here Q×f refers to the product between Q factor and resonant frequency which remains constant even if the resonator resonates at other frequencies. The f is of the order of -50 ppm/oC. On the fabrication process, the sintering temperature of ZnNb2O6 lies in the range of 1050℃ - 1300℃ which is advantageous [1,2]. To improve the Q×f , it is possible to replace Nb5+ with suitable ion either by heterovalent or homovalent ions [3]. There are other few compounds like Zn2Te3O8, that possess high Q factor with ultra-low sintering temperature (585℃ - 610℃) which makes them suitable for LTCC (Low temperature co-fired ceramics) applications [4,5]. Zn2Te3O8, belonging to the family of spiroffites, has not been explored much in the aspect of microwave dielectric studies. The effect of heterovalent ion substitution in Te site on microwave dielectric properties is an interesting aspect to be explored. In this work, we investigate the effect of heterovalent ion substitution in B site of ZnNb2O6 and Zn2Te3O8 on structure, morphology and microwave dielectric properties.
References:

[1] Hyo-Jong Lee, In-Tae Kim, Kug Sun Hong, Dielectric Properties of AB2O6 Compounds at Microwave Frequencies (A = Ca, Mg, Mn, Co, Ni, Zn, and B = Nb, Ta), Jpn. J. Appl. Phys. 36 (1997) 1318-1320.

[2] Robert C Pullar, Jonathan D Breeze, Neil McN Alford, Characterization and Microwave Dielectric Properties of M2+Nb2O6 Ceramics, J. Am. Ceram. Soc. 88 (2005) 2466–2471

[3] Huang CL, Chen JY, Reduced Dielectric Loss of Modified ZnNb2O6 Ceramics by Substituting Nb5+ with Ta5+, J. Am. Ceram. Soc. 92 (2009) 1845–1848.

[4] Subodh G and Sebastian MT, Glass-Free Zn2Te3O8 Microwave Ceramic for LTCC Applications, J. Am. Ceram. Soc. 90 (2007) 2266–2268.

[5] Sea-Fue Wang, Yung-Fu Hsu, Yuh-Ruey Wang, and Chuan-Chun Sung, Ultra-Low-Fire Zn2Te3O8–TiTe3O8 Ceramic Composites, J. Am. Ceram. Soc. 94 (2011) 812–816.