Structural, dielectric, electrical and piezoelectric properties of Ba4SrRTi3V7O30 (R=Sm, Dy) ceramics

Abstract

Abstract:Polycrystalline samples of Ba 4 SrRTi 3 V 7 O 30 (R=Sm and Dy), members of the tungsten-bronze family, were prepared using a high-temperature, solid-state reaction technique and studied their electrical properties (using complex impedance spectroscopy) in a wide range of temperature (31-500 • C) and frequency (1 kHz -1 MHz). Preliminary structural (XRD) analyses of these compounds show the formation of single-phase, orthorhombic structures at room temperature. The scanning electron micrographs (SEM) provided information on the quality of the samples and uniform distribution of grains over the entire surface of the samples. Detailed studies of the dielectric properties suggest that they have undergone ferroelectric-paraelectric phase transition well above the room temperatures (i.e., 432 and 355 • C for R= Sm and Dy, respectively, at frequency 100 kHz). Measurements of electrical conductivity (ac and dc) as a function of temperature suggest that the compounds have semiconducting properties much above the room temperature, with negative temperature coefficient of resistance (NTCR) behavior. The existence of ferroelectricity in these compounds was confirmed from a polarization study.

Effect of Holmium Doping in Ba5RTi3V7O30 (R = Rare Earth Element) Compound

“…Voids are clearly visible in the micrographs which may be due to the low sintering temperature (1073 K) of the compound. Bragg's angle (2θ) This dielectric anomaly at around 550 K corresponds to ferroelectric-paraelectric phase transition [9]. The peak in ε r -T graph is an indication of ferroelectric behavior of the compound.…”

“…DC conductivity plots show that with an increase in temperature, there is a concomitant increase in the conductivity values. Hence, it shows a negative temperature coefficient of resistance (NTCR) [9]. This type of behavior is indicative of thermally activated charge transport in this material.…”

“…This further corroborates the argument presented above in explaining dielectric behavior of this compound. The reason for its ionic character could be because of oxygen ion vacancies created due to difference in valence state of vanadium [9]. The middle semicircular arc represents the contribution due to grain boundary.…”

Preparation, structure and dielectric properties of tungsten bronze ferroelectrics in SrO-Eu2O3-TiO2-Nb2O5 system

“…Dielectric loss for Sr 4 EuTi 4 Nb 6 O 30 , as shown in Fig.4c, nearly temperature independent below temperature 250 ℃, increases significantly above 250 ℃. The higher dielectric loss in high temperature may be due to the enhancement of conductivity and reduction in the ferroelectric domain wall contribution [14] .…”

Structural and electrical studies of Ba5LaTi3V7O30 compound

“…New materials with TB structure [10][11][12][13] having interesting properties have been discovered. Among them are rare-earth doped niobate-titanate; Ba 5 RTi 3 Nb 7 O 30 (R0Eu, Gd) [14] which show diffuse phase transition [15] with T c variation with rare-earth.…”