Dielectric response near the permittivity maximum in ( Sr 0.8 Pb 0.2 ) TiO 3 ceramic solid solution Lanthanum doped SrBi 2 Nb 2 O 9 ceramics with the chemical formula SrBi 2−x La x Nb 2 O 9 ͑SBLN͒ ͑x =0-0.5͒ have been prepared through conventional solid state route. X-ray diffraction reveals the shrinkage of unit cell of strontium bismuth niobate with incorporation of La 3+ dopant, having no lone pair electrons. Shifting of Raman phonon modes indicates the reduced rattling space of NbO 6 octahedra with increase in La doping concentration. Further, the softening of lowest frequency phonon mode with increasing x in SBLN shows the transition from ferroelectric to paraelectric at room temperature. The dielectric properties for all the compositions are studied as a function of temperature ͑25 to 500°C͒ over the frequency range of 10 kHz-1 MHz. With increase in lanthanum doping concentration the phase transition becomes diffused and transition temperature gets shifted toward lower temperature. A phase transition from normal ferroelectric to paraelectric has been observed via relaxor-type ferroelectrics with increase in x. The frequency dependence of transition temperature was studied in terms of Vogel-Fulcher relation for SBLN ͑x = 0.4͒.

SrBi 2 Nb 2 O 9 (SBN) and SrBi 1.9 La 0.1 Nb 2 O 9 (SBLN) have been prepared through conventional solid state route. The crystallographic orientation of the prepared ceramics was investigated using x-ray diffraction. FTIR spectroscopy indicate the growth of single-phase layered perovskite material. The dielectric properties of prepared ceramics are studied as a function of frequency (10 KHz-1 MHz) at different temperatures (25-500 • C). The phase transition temperature of SrBi 2 Nb 2 O 9 ceramic was found to decrease from 420 • C to 395 • C with La (10%) doping. A slight decrease in the value of dc conductivity at 500 • C from 3.82 × 10 −6 to 2.28 × 10 −6 −1 cm −1 was observed with substitution of La at the Bi-site. The power law behavior of ac conductivity is analyzed as a function of frequency at different temperatures.

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