Ferromagnetic nickel (Ni) nanoparticles were added in <$E roman {(Cu sub 0,5 Tl sub 0,5 )Ba sub 2 Ca sub 2 Cu sub 3 O sub {10- delta}}> (CuTl-1223) superconducting matrix to get Nix/CuTl-1223; x = 0 - 1,00 wt % nanoparticles-superconductor composites. Temperature- and frequency-dependent dielectric properties of CuTl-1223 superconducting phase with different contents of Ni nanoparticles were studied. Different dielectric parameters such as dielectric constant (<$E {epsilon prime} sub r>, <$E {epsilon symbol Т} sub r>), dielectric tangent loss (tan <$E delta>) and ac conductivity (<$E sigma sub ac>) were determined from experimentally measured capacitance and conductance at different frequencies from 10 kHz to 10 MHz and at different operating temperatures from 78 to 290 K. The values of <$E {epsilon prime} sub r> and <$E {epsilon symbol Т} sub r> were found maximal at smaller frequencies and started to decrease at higher frequencies. The value of <$E sigma sub ac> is high at high frequency unlike to <$E {epsilon prime} sub r> and <$E {epsilon symbol Т} sub r>, which is due to release of space charges at high frequencies. Peaks in tan <$E delta> graphs represent the resonance phenomenon at certain frequencies in these samples. Non-monotonic behavior in variation of dielectric parameters with temperature of Nix/CuTl-1223 samples was observed particularly at high temperatures which was due to thermal instability of the system at high temperatures.

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