The polycrystalline compound Ba₅NdTi₃V₇O₃₀ (BNTV) was prepared using high purity (>99.9%) ingredients; BaCO₃, Nd₂O₃, TiO₂, V₂O₅ by Mixed Oxide Method. These materials were mixed in appropriate amount satisfying the stoichiometry of Ba₃Sr₂NdTi₃V₇O₃₀, with formula;

5BaCO₃ + 1/2Nd₂O₃ + 3TiO₂ + 7/2V₂O₅ = Ba₅NdTi₃V₇O₃₀ + 5CO₂

The ingredients were mixed in an agate mortar in air atmosphere for 3 h, followed by wet (methanol) condition to get homogeneous mixture. The mixture was then calcined in an alumina crucible starting from 700˚C in steps of 50˚C and was found to be calcined at an optimized temperature and time (950˚C, 12 h). This process was repeated till the formation of single-phase compound was confirmed by X-ray diffraction technique. After mixing the calcined powder with polyvinyl alcohol (PVA) as binder, cylindrical pellets of 10 mm diameter and 1 - 2 mm in thickness were made by a hydraulic press at a pressure of ~ 5 × 10⁶ N/m². The pellets were then sintered in an air atmosphere at an optimized temperature and time (950˚C, 12 h) The pellets were then polished to make their faces flat and parallel and finally coated with high purity conductive silver paint, and dried at 150˚C for 2 h before carrying out electrical measurements to make them moisture free.

The structure of the material was studied from X-ray diffraction (XRD) and Scanning electron micrograph. The room temperature.XRD pattern of the material was obtained in a wide range of Bragg’s angle 2θ (20˚ ≤ 2θ ≤ 75˚) at a scanning speed of 3˚ min⁻¹ by an X-ray diffractometer (Rigaku, Miniflex) with CuKα radiation (λ = 1.5405 Å) Using high-resolution scanning electron microscope (SEM: JOEL-JSM model: 5800F), the surface morphology of the sample was studied. The dielectric measurement was done in a wide range of temperature (33˚C - 500˚C) and frequency (100 Hz - 1 MHz), using a computer-controlled impedance analyzer (PSM 1735, model: N 4L). Then (P~E) hysteresis loop was recorded on the poled sample at room temperature using a high precision workstation (M/S-Radiant Technologies, Inc. USA).

The XRD pattern of the sample shown in Figure 1 confirms the formation of a single-phase new compound. The reflection peaks were indexed and the lattice parameters were determined in various crystal systems and with cell configurations using computer software “POWDMULT” [7]. A suitable orthorhombic unit cell with lattice parameters: a = 23.0868(26) Å, b = 4.2284(26) Å, c = 6.3899(26) Å were chosen. The crystallite size of the sample was evaluated from the broadening of the peaks (β_1/2) using Scherrer’s equation [8]; P = Kλ/β_1/2 cosθ_hkl, where K = constant = 0.89, k = 1.5405 Å and β_1/2 = peak width of the reflection at half height. The crystallite size of the compound was observed to be 8 nm.

The room temperature scanning electron micrograph of the compound shown in Figure 1 (inset) resembles polycrystalline arrangement of the material with grains of irregular in shape and size distributed non-uniformly and densely over the entire surface of the sample. A similar microstructure is also observed in some of our materials of this family [9][10]. The grain size of the sample from histogram (Figure 1 (right)) was measured to be in the range of 220 nm.

The temperature dependent relative dielectric constant (ε_r) and loss tangent (tan δ) (inset) of Ba₅NdTi₃V₇O₃₀ compoundis shown in Figure 2 at some selected frequencies. Figure 2 describes the decreasing trend of both ε_r and tan δ (inset) with increase in frequency which is exhibited by polar dielectrics. The compound

has a frequency independent dielectric anomaly at ~460˚C indicating the possible occurrence of ferroelectric-paraelectric phase transition. The value of ε_r is more at low frequencies confirms the presence of all types of polarization whereas at high frequencies it is mainly due to the contribution of electronic polarization [11].

The value of loss (tanδ) is observed to be low indicating good quality of the material. The value of tanδ is observed to be increased at higher temperature region (Figure 2 inset) caused by the intensifying conductivity for setting up of space charge polarization, and also due to trimming in ferroelectric domain wall’s contribution at high temperature [11].

The variation of a.c. conductivity (σ_ac) as a function of inverse temperature at two different frequencies (50 kHz and 500 kHz) shown in Figure 3.

Figure 3 obeys the Arrhenius relation: σ_ac = σ₀ exp(−E_a/k_BT), where the symbols have their usual meanings. The plot is divided into two distinct regions as I in high temperature and II in low temperature regions for both the frequencies. From calculation, the activation energy (Ea) are found to be 0.105 eV and 0.051

eV in region-I and 0.5162 eV and 0.464 eV in region-II which are low and different and informs the existence of different conduction mechanisms. The small values of activation energy implies that little amount of energy is sufficient to activate the carriers for electrical conduction. Frequency independent dc conduction is confirmed from merging of the two curves at high temperature.

The ceramics of this family have dielectric breakdown at even low electric field, the saturation polarization could not be observed at the given field; hence we could not get a proper hysteresis loop. The dielectric anomaly in the studied compounds is assumed to be related to ferroelectric-paraelectric phase transition. This assumption was confirmed by appearance of hysteresis loop as seen in Figure 4. Even with smaller remnant polarization the existence of ferroelectric properties in the compounds can be concluded.