Diffuse Phase Transition and Electrical Conductivity of Pb(Ca1/3Nb2/3)O3

The lead-based relaxor ceramic Pb(Ca_1/3Nb_2/3)O₃ was prepared by two-step solid-state reaction. The material stabilizes in the orthorhombic phase with refined lattice parameters a = 3.4814 Å, b = 12.9480 Å, and c = 14.2483 Å. The scanning electron micrograph is indicative of heterogeneous grain distribution with average grain size ~0.8–2.0 μm. The temperature-dependent dielectric response has a broad peak at 233.5°C (at 1 kHz, ε′ = 14523). A frequency-dependent shift toward higher temperature with increasing frequency is attributed to relaxor behaviour. Deviation from the Curie–Weiss law is observed at temperatures higher than the temperature, T _m, at which the dielectric constant is maximum. The modified Curie–Weiss law was used to fit the dielectric data; the results were indicative of almost complete diffuse phase transition characteristics. The dielectric relaxation obeys the Vogel–Fulcher relationship with freezing temperature T _f = 214.1°C, activation energy E _a = 0.16 eV, and relaxation frequency ν ₀ = 3.4 × 10⁷ Hz. Electrical conduction is mainly attributed to the hopping mechanism.