## 3 Results and Discussion
Consequently, to ascertain its aptness for LTCC applications, a thorough examination was undertaken to evaluate the chemical compatibility of a 40 mol% LiF-doped Cu\({}_{0.3}\)Zn\({}_{0.7}\)Ti\({}_{0.2}\)Zr\({}_{0.8}\)Nb\({}_{2}\)O\({}_{8}\) ceramic with silver. To this end, a strategic addition of 20 wt.% silver powder was incorporated into the base powder mixture, which was then subjected to a co-sintering process at a temperature of 950 \({}^{\circ}\)C for a duration of 4 h. Figure 9 shows the XRD pattern and SEM image of the as-tested specimen. Remarkably, apart from the distinct diffraction peaks attributed to Ag, specifically identified as Ag (111) and Ag (200), no discernible secondary phase related to Ag addition was detected, unequivocally indicating the absence of any chemical interaction between the ceramic and the introduced silver particles (Figure 9a). This observation was reinforced by the SEM micrograph in Figure 9b, which distinctly showcased a well-defined interface separating the ceramic matrix from the silver particles. Concurrently, the EDS analysis (Figure S4) precisely pinpointed the chemical composition of Spot B as pure Ag, whereas Spot A was characteristic of the grains comprising the 40 mol% LiF-doped Cu\({}_{0.3}\)Zn\({}_{0.7}\)Ti\({}_{0.2}\)Zr\({}_{0.8}\)Nb\({}_{2}\)O\({}_{8}\) ceramic. These findings unequivocally underscore the excellent chemical stability between the ceramic and the silver electrode at 950 \({}^{\circ}\)C, positioning the 40 mol% LiF-doped Cu\({}_{0.3}\)Zn\({}_{0.7}\)Ti\({}_{0.2}\)Zr\({}_{0.8}\)Nb\({}_{2}\)O\({}_{8}\) ceramic as a highly promising candidate for LTCC applications. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Compound** & **S.T. (\({}^{\circ}\)C)** & \(\epsilon_{r}\) & \(Q\times f\)**(GHz)** & \(\tau_{f}\)**(ppm\({}^{f}\)C)** & **Reference** \\ \hline ZnZrNb\({}_{2}\)O\({}_{8}\) & \(1325\) & \(26.55\) & \(68,300\) & \(-32.92\) & [13] \\ \hline ZnZr\({}_{0.8}\)Ti\({}_{0.2}\)Nb\({}_{2}\)O\({}_{8}\) & \(1150\) & \(29.75\) & \(107,303\) & \(-24.41\) & [14] \\ \hline Zn(Ti\({}_{0.6}\)Zr\({}_{0.4}\))Nb\({}_{2}\)O\({}_{8}\) & \(1120\) & \(33.43\) & \(59,475\) & \(-76.54\) & [34] \\ \hline CoTiNb\({}_{2}\)O\({}_{8}\) & \(1000\) & \(64.19\) & \(16,800\) & \(+66.17\) & [35] \\ \hline ZnTi\({}_{0.97}\)Ge\({}_{0.03}\)Nb\({}_{2}\)O\({}_{8}\) & \(1120\) & \(35.6\) & \(62,700\) & \(-58\) & [36] \\ \hline ZnTi\({}_{0.8}\)Sn\({}_{0.2}\)Nb\({}_{2}\)O\({}_{8}\) & \(1120\) & \(30.88\) & \(43,500\) & \(-54.32\) & [37] \\ \hline Mn\({}_{1.05}\)Ti\({}_{0.9}\)Zr\({}_{0.1}\)Nb\({}_{2}\)O\({}_{8}\) & \(1200\) & \(32.9\) & \(11,427\) & \(0\) & [38] \\ \hline Zn\({}_{0.95}\)Mn\({}_{0.05}\)TiNb\({}_{2}\)O\({}_{8}\) & \(1100\) & \(35.91\) & \(63,672\) & \(-68.68\) & [39] \\ \hline ZnTi\({}_{0.99}\)Mo\({}_{0.01}\)Nb\({}_{2}\)O\({}_{8}\) & \(1150\) & \(33.91\) & \(64,136\) & \(-50.57\) & [40] \\ \hline (Co\({}_{0.35}\)Zn\({}_{0.65}\))TiNb\({}_{2}\)O\({}_{8}\) + 4 wt. \%BaCu(B\({}_{2}\)O\({}_{5}\)) & \(925\) & \(36.7\) & \(19,880\) & \(+14.2\) & [41] \\ \hline Cu\({}_{0.3}\)Zn\({}_{0.7}\)Zr\({}_{0.8}\)Ti\({}_{0.2}\)Nb\({}_{2}\)O\({}_{8}\) + 40 mol\% LiF & \(950\) & \(32\) & \(45,543\) & \(-43.5\) & This work \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The comparison between our reported ceramics with other \(M^{2+}N^{4+}\)Nb\({}_{2}\)O\({}_{8}\)-type ceramics in terms of sintering temperature and microwave dielectric properties. Figure 8: Relative densities and microwave performance of Cu\({}_{0.3}\)Zn\({}_{0.7}\)Ti\({}_{0.2}\)Zr\({}_{0.8}\)Nb\({}_{2}\)O\({}_{8}\) supplemented with \(y\) mol% LiF (\(10\leq y\leq 50\)).