This article reports the relationship between microstructure and dielectric properties of the title material were prepared through combination of solid-state and sol–gel methods and then sintered by varying durations. XRD indicates Im-3 space group with a body centred cubic structure, and Rietveld refinement analysis showed good fits for all samples, with R-factors below 10 % and GoF less than 2. The XPS analysis revealed the existence of Ca 2p, La 3d, Cu 2p, Ti 2p, O 1s, and C 1s retained their correct oxidation states. SEM results show grain sizes of 1.10 (±0.25) μm, 1.24 (±0.10) μm, and 1.75 (±0.31) μm for 8, 12, and 16 h of sintering, respectively. EDS analysis confirms the presence of Ca, Cu, Ti, La, and O, indicating the purity of the ceramics. As the sintering duration increases, grain enlargement consistently leads to higher εr values with very low tanδ. At a low frequency of 50 Hz, εr increases with sintering duration, reaching values of 5.65 × 103, 5.90 × 103 and 9.94 × 103. Meanwhile, tanδ remains significantly low (<0.1) at 1 kHz. The Nyquist plots demonstrate deviation from Debye type relaxation with NTCR behaviour. The frequency-dependent AC conductivity follows Jonscher’s power law, with activation energy values of 0.44 eV, 0.46 eV, and 0.49 eV for ceramics sintered for 8, 12, and 16 h, respectively.