Understanding structure-composition-property correlation is very important in optimal design of efficient functional materials. Pyrochlore materials are considered a great exponent for ‘materials for society’ owing to their several multifunctional properties in the area of health, energy and environment. We have synthesized Gd₂Zr_2-xHf_xO₇ : Eu (0.0 0 ≤x ≤2.0 0) and explored it’s structural and optical properties using Rietveld refined X-ray diffraction (XRD), time resolved photoluminescence (TRPL) and positron annihilation lifetime spectroscopy (PALS). Emission spectra depicted asymmetric environment around europium ion in all the samples with higher value in solid solution compared to Gd₂Zr₂O₇ :Eu³⁺ (GZOE) and Gd₂Hf₂O₇ (GHOE) which is in line with trend in Judd-Ofelt parameters. XRD measurement has suggested incorporation of Hf⁴⁺ into the Gd₂Zr₂O₇ structure leads to strengthening of Gd-O bonds within the structure whereas weakening of Zr/Hf-O bond was observed (try to include Raman spectra also) with creation of more number of smaller vacancy clusters than GHOE and GZOE. Average lifetime consistently increases as we move from GZOE to GHOE wherein Zr4+ are gradually being replaced by Hf4+ sites endowed by more symmetric environment around Eu3+ as Hf4+ content is increased or having GHOE as more ordered system than GZOE. Internal Quantum efficiency (IQY) was found to be higher for solid solution compared to end members GZOE and GHOE. The end members have more sources of non-radiative channels and low asymmetry ratio. We believe this work will give much sought out information in designing lanthanide ion doped pyrochlore for red emitting phosphor for phosphor converted LEDs.