Effect of CuO on the sintering and cryogenic microwave characteristics of (Zr_0.8Sn_0.2)TiO₄ ceramics

Abstract

The effect of CuO on the sintering temperature, microstructure and microwave dielectric properties of (Zr 0.8 Sn 0.2 )TiO 4 (ZST) modified with 1 wt% of ZnO has been investigated. Microwave dielectric properties of ZST ceramics are measured from cryogenic to room temperatures (15-290 K). Crystallite sizes of sintered ZST ceramics as derived from XRD are in the 30-50 nm range. The addition of CuO effectively reduced the sintering temperature to 1300 1C, possibly due to liquid-phase effects. Addition of CuO did not cause any secondary phases up to 1.5 wt% of CuO. The dielectric constant (e r ) and temperature coefficient of resonant frequency (t f ) of ZST ceramics do not significantly vary with temperature, whereas the unloaded quality factor (Q u ) changes noticeably. It is found that the Q u factor of the sample without CuO decreased with increase in temperature, whereas the samples with addition of CuO up to 1.0 wt% showed less dependence on temperature. The Q u factor of CuO-free ZST is 15,000 and that of ZST with 0.5 wt% of CuO is 11,800 at 15 K. The Q u factor while measured at room temperature ranged between 2900 and 7000. Efforts were made to understand whether the increase in Q u factor at both cryogenic and room temperatures is the result of intrinsic or extrinsic factors. r

Fundamental mechanisms responsible for the temperature coefficient of resonant frequency in microwave dielectric ceramics

“…A number of other studies have measured τ f using a TE 01δ or TE 011 resonance mode of dielectric resonators16‐22 and assumed that this is equal to τ ε , neglecting the contributions from α L and τ u . From the literature and the measurements reported here, we note that α L can be on the order of 5‐10 ppm/K at 200 K and above for most microwave oxide ceramics, whereas τ u can be of the same order at very low temperature in paramagnetic‐laden dielectrics .…”

“…From the literature and the measurements reported here, we note that α L can be on the order of 5‐10 ppm/K at 200 K and above for most microwave oxide ceramics, whereas τ u can be of the same order at very low temperature in paramagnetic‐laden dielectrics . Since these References16‐22 directly measured τ f , we will only summarize their findings in that light. Subodh et al found that as the temperature increases, the τ f of V 2 O 5 ‐doped Mg 2 TiO 4 dielectrics is ~−30 ppm/K at low temperatures and increases to ~−50 ppm/K above 150 K. An investigation of V 2 O 5 ‐doped Mg 2 TiO 4 ceramics by Bhuyan et al and single‐crystal LaAlO 3 found that τ f is positive at low temperature, increasing slowly as the temperature is raised to ~150‐200 K, then increasing more rapidly above 150‐200 K. Similarly, Pamu et al found that τ f of CuO‐doped Zr 0.8 Sn 0.2 TiO 4 is ~9 ppm/K from 10 to 250 K and then increases significantly up to room temperature .…”

Microwave dielectric properties of low temperature fired Ba5Nb4O15 ‐ BaWO4 ceramics supplemented with their own nanoparticles for LTCC applications

“…[1][2][3][4][5][6] There are large number of microwave dielectric materials have been studied for these applications and among them Ba 5 Nb 4 O 15 -BaWO 4 composite ceramics have been studied broadly due to their promising microwave dielectric properties at lower sintering temperatures: e r= 16.9-21, Q9ƒ 0 =49 500-56 700 GHz and s f =8.9 to À4.3 ppm/°C. Microwave dielectric materials are continuing to play a very significant role in the microwave communication systems.…”

“…The importance of good quality dielectric resonators in the microwave technology is increasing and there are few essential requirements, which are required for microwave applications, i.e., good dielectric constant(e r ), a high quality factor (Q 9 ƒ 0 ) and a near-zero temperature coefficient of resonant frequency (s f ). [1][2][3][4][5][6] There are large number of microwave dielectric materials have been studied for these applications and among them Ba 5 Nb 4 O 15 -BaWO 4 composite ceramics have been studied broadly due to their promising microwave dielectric properties at lower sintering temperatures: e r= 16.9-21, Q9ƒ 0 =49 500-56 700 GHz and s f =8.9 to À4.3 ppm/°C. 7,8 In the recent years, the Low temperature co-fired ceramics (LTCC) technology is widely used for miniaturization of microwave devices to reduce the size of wireless communication systems and this technology is well-known both for high volume, low cost application (wireless communication, car industry) and low volume high performance applications (military and space).…”

“…[9][10][11][12] The recent development of LTCC technology is demanding for high frequency wireless communication systems, which is an advanced approach to fabricate the ceramic structures with high speed and high frequency processing devices in the electronic industry. 13 In the present work, we developed Ba 5 Nb 4 O 15 -BaWO 4 composite ceramic matrix system with the addition of their own nanoparticles of Ba 5 Nb 4 O 15 and BaWO 4 and studied their effect on sintering temperature on their physical properties such as structural, microstructural, and microwave dielectric properties of the prepared composite ceramics. However, to the best of the author's knowledge there is no study available on the preparation of nanoparticles of BNO and BWO ceramics and their addition as a sintering aid to BNO -BWO composite ceramics, hence this study.…”