We report a detailed study on structural and dielectric properties, Raman scattering, and ac-conductivity of ferroelectric KNbO ₃ and antiferromagnetic NiO two-phase composites [(

1 ​ ​ - ​ ​ x

) KNbO ₃ + x NiO]. Two major transitions were observed in the temperature dependent relative dielectric permittivity

ϵ_{r}

( T )—the first at

445^{\circ}

C (

T^{*}

) and the second at

220^{\circ}

C ( T ₁ )—respectively associated with the structural transitions from tetragonal to cubic and orthorhombic to tetragonal phases. In addition, a new anomaly across T ₂ ∼

320^{\circ}

C has been observed in

ϵ_{r}

( T ), and the loss-tangent (Tan δ (T)), which may be associated with the combined effect of antiferromagnetic ordering of NiO and ferroelectric coupling of KNbO ₃ . The dispersive nature of

T^{*}

, and the Vogel–Fulcher temperature dependence of its characteristic relaxation frequency reveals the existence of relaxor-like behavior, which is further supported by Uchino–Nomura criteria (for x ⩽

0.10

) but departs from relaxor behavior for x

>

0.10

. Temperature dependent ac-resistivity analysis

ρ_{a c}

( T ) provides strong evidence for a Mott’s Variable range hopping process of charge carriers between localized states, with average hopping length of

4.2

nm and hopping energy

0.72

eV. The variation of

T^{*}

, T ₁ and T ₂ as a function of x , in consonance with the crystal structure, has been discussed. Raman spectroscopic studies were carried out to study the local structure of the (

1 ​ ​ - ​ ​ x

)

{K N b O}_{3}

+ x NiO two-phase composites, which shows significant increase of tilt-angle between adjacent

{N b O}_{6}

octahedra as the divalent Ni occupies octahedral sites of the

{K N b O}_{3}

matrix. All the Raman-active modes of these composites are indexed as lattice translations, specifically with the motion of

K^{+}

(190

{c m}^{- 1}

), the core vibrations of the

{N b O}_{6}

octahedra (220

{c m}^{- 1}

⩽ ν ⩽ 320

{c m}^{- 1}

) and their collective modes (50

{c m}^{- 1}

⩽ ν ⩽ 150

{c m}^{- 1}

), and Magnon modes (2M ∼ 1500

{c m}^{- 1}

) associated with the antiferromagnetic ordering of NiO.

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