Enhancement of nonlinear optical and temperature dependent dielectric properties of Ce:BaTiO3nano and submicron particles

Abstract

The solgel synthesized Ce: BaTiO3 (BT) particles are crystallized in tetragonal structure and the expansion of lattice along a-axis is ensured from the Rietveld refined XRD spectra. FTIR shows that the increase of force constant from 199.97 to 213.13 N m⁻¹ is owing to an effective incorporation of heavier atomic mass of Ce in BT lattice. HRTEM reflects the discontinuous atomic planes in the form of Ti vacancies which is supported by EDS measurement. The modification of optical band structure of BT with Ce ions is validated through several absorption and defect emission bands. Energy dependent second harmonic generation is carried out to confirm the non saturated signal, thermal stability and maximum intensity 2483 counts attained for 2 mol% Ce at 200 mJ. Optical limiting characteristics of the samples is analysed at 532 nm using 5 ns laser pulses of energy 50, 100 and 150 µJ. The nonlinear absorption coefficient (β) is found to be enhanced upon Ce doping. Lower optical limiting thresholds of 2.8 and 3.3 J cm⁻² are obtained in the case of 1 and 4 mol% Ce samples respectively. Dielectric properties in a broad temperature range (40–500 °C) and frequency (100 Hz–5 MHz) have been investigated in detail. The dielectric constant is increased from 1926 to 3750 on Ce doping and there are two semicircles in the Cole–Cole plot at 500 °C due to grain and grain boundaries and corresponding equivalent circuit model is proposed.