Influence of La doping on structural and dielectric properties of SrBi2Nb2O9 ceramics

Abstract

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.

Structural, dielectric and piezoelectric properties of SrBi2Nb2O9 and Sr0.8Bi2.2Nb2O9 ceramics

“…The intense Raman bands were found at 76, 176, 203, 449, 574 and 833 cm À 1 and weak Raman bands at 93, 151, 227, 274, 305, 558, 591, 802 and 855 cm À 1 , which are in good agreement with those are reported by Nelis et al [36]. The Raman bands can be assigned as follows: the bands below 200 cm À 1 represent the vibration mode of Sr 2þ ions at the A-site in the perovskite layer and the bands above 200 cm À 1 represent the internal modes of NbO 6 octahedral [37][38][39][40]. The band observed at 76 cm À 1 , assigned as a 'rigid layer' mode which reflect the Bi 3þ ions vibration in Bi 2 O 2 layers, no change in its position was observed with increasing Bi content.…”

Structural and optical properties of Bi 2 VO 5.5 thin films deposited on silicon substrates

“…The band at 858 cm -1 represents the symmetric stretching of VO 3.5 □ 0.5 octahedra [12,13] . Since Raman scattering is sensitive to the variations of local structures [14] , the effect of annealing temperature on the local structure could be shown in Raman spectra. The Raman band at 858 cm -1 which represents the symmetric stretching of VO 3.5 □ 0.5 octahedra is the strongest of all the Raman peaks.…”

Selective Synthesis of Silver Nanoparticles onto Potassium Hexaniobate: Structural Organisation with Bactericidal Properties

“…The peak at 850 cm À1 is attributed to the symmetric stretching of NbO 6 octahedra, while the band at 540 cm À1 is assigned to the tilting of the NbO 6 octahedra. [31,32] Layered ceramics [32] and hexaniobate [33] showed similar changes in the Raman profile after cation exchange, which are attributed to differences in species size [32,33] and to different degrees of interaction with water molecules. [33] Analogously, the band shift to higher frequencies observed here is attributed to the shrinkage of NbO 6 octahedra interacting with silver ions, resulting in an increase in the bond order of NbÀO.…”