This study is set out to investigate Pb-free weak ferroelectric pure and Li-doped AgNbO3, AgTaO3 and Ag(Nb0.5Ta0.5)O3 ceramics. The basic aim was two-pronged; (i) to synthesize all compositions, particularly AgTaO3 and the ones Ta-rich (as these compositions are very difficult to fabricate), via solid state reaction route and optimize the processing parameters, and (ii) to investigate the effect of Li-substitution on the crystal structure, microstructure and electrical properties of these systems. Thermogravimetric (TG) and Differential Thermogravimetric Analyses (DTA), high resolution synchrotron X-ray, Neutron Diffraction, Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive Spectroscopy (EDS) and Raman Spectroscopy were used to characterize the samples. Inductance Capacitance Resistance (LCR) meter was used to measure dielectric properties. The first set in the solid solution series (LixAg1-x)NbO3 (x = 0.00, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10) was characterized by Synchrotron X-ray Diffraction (S XRD), Neutron Powder Diffraction (NPD) and Raman spectroscopy. Rietveld refinements against both the S-XRD and NPD spectra revealed that pure AgNbO3 crystalized in orthorhombic structure (Pmc21) with a unit cell √2ap× √2ap×4ap (where ap is the fundamental perovskite lattice parameter). The sample with x = 0.10 has rhombohedral (?3?) symmetry with a √2?? × √2?? × √12?? unit cell.The composition induced orthorhombic - rhombohedral phase transition started at x ~ 0.05 and completed by x ~ 0.07. Both phases coexisted in the region with 0.05 ≤ x ≤ 0.07. The Raman spectra were consistent with the S-XRD and NPD data thereby confirming the onset of the structural phase transition in the 0.05 ≤ x ≤ 0.07 composition range. Temperature dependent dielectric measurements revealed enhancement in ferroelectric rhombohedral distortion with increasing Li-concentration resulting increase in the polarization of the solid solutions. Temperature dependent S-XRD measurements of AgNbO3 revealed the phase transition sequence to be: ???21 ~67 °C ↔???? ~357 °C ↔???? ~377 °C ↔?4/??? ~607 °C ↔??3 ̅?. The second system investigated in the present study was (LixAg1-x)TaO3 for x = 0.00, 0.01, 0.02, 0.03, 0.04, and 0.05. Phase purification was checked using instrumental X-ray diffractometer (XRD). These samples were also characterized by S-XRD, NPD and Raman spectroscopy. Rietveld refinements against both the S-XRD and NPD data showed that pure AgTaO3 crystalized in rhombohedral structure with space group R3c, √2?? × √2?? × √12?? (where ap is the fundamental perovskite lattice parameter). No significant changes were observed in S-XRD and NDP as a function of increasing lithium content. The sole significant phenomenon observed was peak shifting towards higher angles, indicative of a decrease in volume with smaller lithium induction for silver cations. Temperature dependent Raman spectroscopy indicated that below room temperature, Li doping induced a structural phase transition in AgTaO3. Temperature dependent dielectric measurements indicated increase in dielectric constant with increasing Li concentration. The temperature dependence of the structure of the two end members, AgTaO3 and (Li0.05Ag0.95)TaO3, was studied using in-situ Synchrotron X-ray powder diffraction methods. This work found no evidence for the presence of a monoclinic phase. Instead, four phases have been identified, namely ?3? ~390 °C ↔???? ~465 °C ↔?4/??? ~580 °C ↔??3 ̅?. The co-existence of the rhombohedral and orthorhombic phases around 380 – 400 °C indicated that the transition was of first order and gave rise to the observed unusual peak shapes in the diffraction patterns. The phase transition sequence for (Li0.05Ag0.95)TaO3 is similar to the one in pure AgTaO3 and is given as ?3? 480 °? ↔ ???? 510 °? ↔ ?4/??? 560 °? ↔ ??3 ̅?. In the third phase, solid solutions of Ag(NbxTa1-x)O3 for x = 0.72, 0.73, 0.74, 0.75, 0.76 and 0.77 samples were studied. Phase purity was checked using XRD. SEM (equipped with EDX system) was used to check the microstructure and elemental composition of the samples. SEM micrographs showed reasonably dense microstructure with grains of size 2-5 μm. These samples were also characterized by S-XRD and Raman spectroscopy. Rietveld refinements against the S-XRD data showed that Ag(NbxTa1-x)O3 (for all x values) crystalized in orthorhombic, Pbcm, structure with√2?? × √2?? × 4?? parameters (where ap is the fundamental perovskite lattice parameter). No significant changes were observed in S-XRD with increasing tantalum contents. Raman spectroscopy exhibited some spectral changes with varying temperature. Both XRD and Raman results were compared with those of pure AgNbO3 to see structural changes as a consequence of replacement of Nb+5 with Ta+5.