Structure properties and dielectric relaxation of Ca0.1Na0.9Ti0.1Nb0.9O3 ceramic.

In this paper, the synthesis of Ca0.1Na0.9Ti0.1Nb0.9O3 (CNTN) ceramic by a solid-state reaction method is reported. The results of Rietveld refinement of X-ray diffraction (XRD) patterns at room temperature showed a pure tetragonal perovskite (P4mm space group). Raman spectroscopy analysis, ranging from of 50 to 1000 cm-1, at room temperature, validates the results of XRD. The dielectric properties was studied by complex impedance spectroscopy examined in broad frequency range, 100 Hz to 200 kHz, at different temperatures. The dielectric permittivity for our CNTN compound confirms the typical relaxor behavior. The investigation of the diffuseness of the transition was conducted by fitting the experimental data with modified Curie-Weiss law; Gaussian distribution and Power law confirm the presence of a short-range association between the polar nanoregions (PNRs). The obtained values of the diffuseness coefficient are of the order 1.6, which corresponds to the diffuse phase transition (DPT) ascribed to the existence of various states of polarization, thus various relaxation times in different regions. The value of diffuseness is of the order 85 and the degree of relaxor (ΔT cm = 65 K) is interesting as far as microelectric applications are concerned. Moreover, based on the frequency dependence of temperature at dielectric maxima using Vogel-Fulcher relationship, a strong evidence for a static freezing temperature with regards to thermally-activated polarization fluctuations was found.

The investigation of structural and vibrational properties and optical behavior of Ti-doped La0.67Ba0.25Ca0.08Mn(1-x)Ti x O3 (x = 0.00, 0.05 and 0.10) manganites.

The influence of Ti4+ ions incorporated into the B site on the structural, vibrational and optical properties of La0.67Ba0.25Ca0.08Mn(1-x)Ti x O3 (LBCM(1-x)T x ), a polycrystalline compound prepared by a molten salt method, was discussed. The X-ray diffraction (XRD) studies confirmed that at room temperature these compounds crystallize in the rhombohedral phases of R3̄c. Rietveld refinement indicated that the octahedron (Mn/Ti)O6 underwent a slight deformation and the θ (Mn/Ti)-O-(Mn/Ti) bond angles decreased with the increase in the Ti content. Furthermore, Raman spectra were recorded at room temperature for the LBCM(1-x)T x ceramics to investigate the influence of incorporated Ti4+ ions in LBCM(1-x)T x . Moreover, we controlled the frequency and damping of the optic modes based on Ti incorporation. The infrared (IR) absorption spectrum (FTIR) analysis in the span of 420-750 cm-1 supports the XRD results. The diffuse reflectance data at room temperature verified that both transition levels (5Eg → 5T5g) and (4A2g → 4T2g) correspond to the Mn3+ and Mn4+ ions. The optical band gap (E g) values decreased from 2.90 eV to 2.70 eV with the increase in the Ti4+ content, implying that our samples could be good candidates for some applications in luminescent devices, such as ultrafast optoelectronic devices. Moreover, the photoluminescence spectra (PL) features at room temperature decreased for all samples. CIE were estimated for all the concentrations of Ti4+ ions. The results indicated that are a shifts in the CIE values of the compounds.