Preparation, characterization, and dielectric properties of wolframite-structure MnZrNb 2 O 8 ceramics at microwave frequency

Low temperature sintering and microwave dielectric properties of MnZrNb2O8 ceramics with H3BO3 addition

“…GHz and t f ¼ À8.4 ppm/ C, which were superior than the properties of the pure phase MnZrNb 2 O 8 ceramics in our previous report [14].…”

“…As the sintering temperatures increasing from 1050 to 1250 C, the apparent densities of the samples increased and the maximum apparent densities were obtained at 1250 C. Fig. 3(b) illustrated the relationship between H 3 BO 3 contents and apparent densities of the MnZrNb 2 O 8 ceramics sintered at 1250 C. It was reported in our previous work that the relative density of the pure phase MnZrNb 2 O 8 ceramics was around 95% with the addition of 1 wt% H 3 BO 3 at 1250 C [14]. With the amounts of H 3 BO 3 increasing to 1 wt%, the apparent densities significantly increased from 5.03 to 5.20 g/cm 3 .…”

“…2(b), it was demonstrated that the liquid phase at the grain boundary effectively eliminated the pores and increased the apparent density of the samples. For the 1 wt% H 3 BO 3 -added ceramics, the obtained apparent density of 5.20 g/ cm 3 at 1250 C was corresponded to that of the pure phase MnZrNb 2 O 8 ceramics sintered at 1325 C [14]. Thus, it was considered that the small amount of H 3 BO 3 doping played an important role in decreasing the sintering temperature and improving the apparent densities.…”

“…In our previous work, the microwave dielectric properties of pure phase MnZrNb 2 O 8 ceramics had been investigated systematically as a function of sintering temperatures. The ceramic sintered at 1250 C for 4 h had a dielectric constant of 24.62, a Q·f value of 27,936 GHz and a temperature coefficient of À52.11 ppm/ C [14]. However, the high sintering temperature limited the applications of the ceramics in microwave devices.…”

The latest process and challenges of microwave dielectric ceramics based on pseudo phase diagrams

“…5, and the related investigations of each structure are illustrated in this section. The effects of different cations (Mn, Zn, Mg, Ni, and Co) at A-site of AZrNb 2 O 8 illustrated that dielectric constant, quality factor, and τ f values relied on the ionic polarizability, packing fraction, and B-site octahedral distortions, respectively [80][81][82][83][84][85]. Among them, MgZrNb 2 O 8 shows the optimal quality factor www.springer.com/journal/40145 (ε r ≈ 26, Q×f value ≈ 120,816 GHz, and τ f ≈ -50.2 ppm/ , ℃ at f = 6.85 GHz [86]).…”