The polycrystalline sample Li_0.5Bi_0.5Ti_0.8Zr_0.2O₃ (LBTZ) was prepared with apposite stoichiometric ratio of precursors; LiCO₃, Bi₂O₃, TiO₂, ZrO₂ of high purity (>99.9%) were weighed and blended mechanically by an agate mortar for about 3 h. The powders were then calcined at optimized temperature and time (900˚C for 12 h) in air condition. The calcined powder thus procured was blended with PVA (poly vinyl alcohol) binder, grinded and were palletized ensuingly (about 10 mm in diameter and 1 - 2 mm thickness) under uniaxial pressure of 4 × 106 N/m². Thereafter the pellets were sintered in air atmosphere at 950˚C for 12 h. Ultimately the pellets were laminated with high purity silver paint, and then heated at 150˚C for 2 h before executing the electrical measurements.

X-ray diffraction (XRD) pattern of the material procured in a vast range of Bragg angle 2θ (200 ≤ 2θ ≤ 800) at a scanning speed of 30 min⁻¹ by an X-ray diffractometer (Rigaku, Miniflex) with CuKα radiation (λ = 1.5405 Å) at room temperature. The surface morphology of the pellet sample of the material was recorded with a high-resolution scanning electron microscope (SEM: JOEL-JSM model: 5800F). The dielectric characterisation of the sample was prosecuted in the temperature range of 32˚C - 5000˚C and frequency range of 1 kHz to 1 MHz, using a computer-controlled Hioki HiTester LCR meter.

Figure 1 shows the XRD pattern of the sample. Indexing of all the peaks of the

pattern were done taking their 2θ values bya computer program package, “POWDMULT” [9] in distinct crystal system and cell configuration and are traced to be sharp and solo, which The peaks are discrete from those of ingredients ensuring the evolution of new single-phase compound. On the basis of the best agreement (based on least-squares refinement) between scrutinised (obs) and reckoned (cal) interplaner distance d (i.e., Σ(d_obs − d_cal) = minimum), an orthorhombic unit cell was selected with lattice parameters: a = 18.8065 (29) Ǻ, b = 8.3211 (29), c = 8.2920 (29) Ǻ (estimated standard deviation in parentheses) which are consistence with the reported ones [10] . The coherently average dispersed crystallite size (D) of the compound was computed to be ~ 15 nm using Scherrer’s equation; D = 0.89λ/(β_1/2cosθ_hkl), where λ = 1.5405 Å and β_1/2 = peak width of the reflection at half maxima [11] . The contributions of strain, instrumental error and other unknown effects in the peak broadening has not been taken into board during the crystallite size enumeration.

The room temperature SEM micrograph (Figure 1 (inset)) of the LBTZ compound, confirmed homogenously and non-uniform distribution of the grains over the entire surface of the sample. The grain size evaluated from the histogram Figure 1 (right) is traced to be of 4.9 μm. As expected, the grain size of the sample obtained here is gigantic in comparison to the crystallite size enumerated from Scherrer’s equation. Thus, a solo grain has large number of crystallites [12] .

The temperature variation of relative dielectric constant (ε_r) at some selected frequencies of compound is shown Figure 2. The plot firmly established the ferro to paraelectric phase transition at 112˚C. The value of ε_r is small at low temperatures which increases with rise in temperature. The dielectric constant (ε_r) at frequencies 10, 50, 100, 500 and 1000 kHz are found to be 225, 203, 159, 145 and 125 respectively at the transition temperature. The variation of tanδ follows the same pattern as that of ε_r. The increase in the value of tanδ may be due to (i) enhancement in the conductivity and (ii) reduction in the contribution of ferroelectric domain wall [13] .

The ac electrical conductivity (σ_ac) is calculated using the dielectric data and an empirical relation. σ_ac = ωε_rε₀ tanδ, where ε₀ = permittivity of free space and ω = angular frequency. Figure 3 shows the variation of σ_ac as a function of temperature at frequencies 10 and 100 kHz.

The nature of the variation (Figure 3) is almost linear over a wide temperature region obeying the Arrhenius relation: σ_ac = σ₀ exp(−E_a/k_BT) [14] , Each of graph is divided into two different regions independently of frequency. Every divided region is characterized by different slopes showing different activation energy. The solid line of figure shows the linear fit. The activation energy calculated from the slope of the curve at different temperatures has been compared in Table 1. Due to the dielectric phase transitions, abnormality in conductivity was

observed for all the compound at temperatures nearly equal to its Curie temperature, which might be due to the dielectric phase transition. The value of σ_ac increases with increase in temperature indicating negative temperature coefficient of resistance (NTCR) behavior. The increase in conductivity is due to the hopping action of the ions because of thermally activated electrons. At high temperature higher value of activation energy indicates that conductivity is for the movement of oxygen vacancies. Activation energy is low at high frequency as compared to that at the low frequency (Table 1). This is because at low frequencies the overall conductivity is the result of hopping of charge carriers over a large distance and at higher frequencies is restricted to only nearest neighboring defects sites [15] .