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

• Published in: Journal of electronic materials 2014-05, Vol.43 (5), p.1403-1410
• Main Authors: Bajpai, P. K., Pastor, Mukul, Singh, K. N.
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Conductivity; Cross-disciplinary physics: materials science; rheology; Dielectric loss and relaxation; Dielectric properties of solids and liquids; Dielectrics; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Diffusion; Electric currents; Electronics and Microelectronics; Exact sciences and technology; Instrumentation; Materials Science; Optical and Electronic Materials; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Scanning electron microscopy; Solid State Physics; Solidification; Structure of solids and liquids; crystallography; Structure of specific crystalline solids
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-014-2979-7

The lead-based relaxor ceramic Pb(Ca 1/3 Nb 2/3 )O 3 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 μ m. 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 × 10 7 Hz. Electrical conduction is mainly attributed to the hopping mechanism.