Initially 6 g graphite powder was purified. 60 ml Hydrofluoric acid (HF) was added to the 10 g graphite powder and magnetically stirred four one hour. Then deionized water (DIW) was added to it and washed until pH neutralized to 7. At 100˚C, graphite sample was dried by using magnetic stirrer. Now graphite was purified so modified hummers method could start for the synthesis of graphene oxide. 36 g of potassium permanganate (KMnO₄) and 6 g of graphite powder were stirred for mix-up; for several minutes. Another solution was prepared by mixing 720 ml sulfuric acid (H₂SO₄) with 80 ml phosphoric acid (H₃PO₄) and stirred for several minutes. Now add the solution of (KMnO₄ + Graphite) in solution of (H₂SO₄ + H₃PO₄) slowly. After stirring 12 hours the solution changes its color to dark green. Then 800 ml deionized water (DIW) and 10 ml hydrogen peroxide (H₂O₂) added to GO solution and stirring it 10 minutes for the removal of excess KMnO₄. Now reducing the temperature of occurred exothermic reaction by ice bathing. Now for neutralization of GO solution it was washed several times with HCl and DIW. Washing of solution continue until its PH becomes 7 or neutralized. To obtain graphene oxide (GO) powder the washed graphene oxide solution was dried at 70˚C for 24 hours by using oven [14] [15] [16].

For Reduction of graphene oxide (GO) we dispersed graphene oxide powder into DI water at the rate of 0.2 mg/ml. The solutions of graphene oxide (GO) were sonicated in an ultrasound bath for 2 hours. Then the dispersed solution of GO was placed into autoclave and heat at 180˚C for 4 hours [17]. The internal pressure of 400 KPa was applied into autoclave. After heating, the autoclave was cool down to ambient temperature naturally [18]. The sample of reduce graphene oxide was collected and washed with DI water to dry at room temperature overnight to obtain powder of reduce graphene (rGO) [17] [19].

The ceramic based composite was prepared with two different powders. The 1^st one is Sodium bismuth titanate (NBT), which was added as matrix and the 2^nd one was reduce graphene oxide (rGO) which used as filler in the martix. The milling of materials was done for four hours at 200 rev/mint using zirconia balls as grinding media in Teflon jars in a planetary milling. Ethanol was used as a dispersant. Ball milled powders were heated at 70˚C for one day. Drying process was done for the removal ethanol [3] [20] [21] [22].

We prepare four sample with different weight percentage (%) of reduce graphene in NBT (0.5%, 1%, 3%, 5% in 3 g of NBT). These powders were mixed by ball milling technique. Then the powder of composite is collected by filtration [23].

Pressing is the technique of fabricating ceramic components by the compaction of powder in a metal die set. Then the sample were placed between the platen 1 & 2 in a uniaxial hydraulic press for the formation of pellets of weight of 0.5 g [24]. Each sample placed under hydraulic press for 15 mints and pressure buildup of 3000-pound square per meter (PSM). Then the pellets were baked and sintered under high temperature of 1075˚C for 2 hours in a box furnace [4] [22] [25] [26].

NBT/rGO ceramic composites were examined under optical microscopy. This technique is simplest and easy to find reduce graphene in sodium bismuth titanate structure. The dispersion of rGO in the ceramic can be detected by the optical microcopy images [11] [29]. The optical images of ceramic composites are showed in the given Figure 3.

Figure 3(a) shows image of pure NBT and Figures 3(b)-(d) represent 1%, 3% and 5% concentration of reduce graphene in the NBT ceramic material at 50× magnification. In images of ceramic composites, shiny material which is graphene distributed over the NBT matrix representing that the reduce graphene oxide filler was successfully dispersed in the NBT. In these optical image’s spots on the surface of NBT represent the concentration of rGO where BNT ceramic is matrix and rGO is 2D filler. We can see rGO clearly as we increase the percentage of concentration in matrix [30].

In this work sample is attached to probs of the LCR meter and placed in an electrical heater and temperature increases in discrete manners up to 500˚C. The sample is coated by silver paint and LCR is done at frequency between 100 Hz to 1 MHz at different temperature starting from 25˚C with a difference of 25˚C for each reading [10]. The capacitance and resistance of material are obtained by the

LCR meter [31]. We can calculate the conductivity with the given formula;

R = ρ L A

Now we can explain the electrical conductivity of NBT ceramic and rGO/NBT composite which is doped by reduced graphene oxide rGO with different wt% (1%, 3% & 5%). As the concentration of rGO increases in the sample it shows decrease in electrical conductivity. We draw a graph of LCR meter between frequency and conductivity with sodium bismuth titanate doping by reduced graphene oxide with different weight percentage (Figure 4).

Firstly, we analysis electrical conductivity at (200˚C, 300˚C, 400˚C & 500˚C) which shows decrease in the conductivity as temperature from 200˚C to 500˚C at different values as shown in the graphs of NBT ceramic and rGO/NBT composite of different wt% (1%, 3% & 5%) [24] [32]. The impedance spectroscopy shows that conductivity of ceramic composite decreases as the concentration of rGO increases in the composite.

This shows that when rGO was added to piezoelectric ceramic, it become

semimetal composite of zero band gap [33]. The value of electrical conductivity of conducting composite shows decreases as wt% of filler increases in the composite in Table 1. The LCR Meter show results that conductivity of ceramic composite decreases at 1 MHz as the concentration of rGO increases in the composite. This shows that when rGO was added to NBT, it become semimetal composite of zero band gap. The electrical conductivity of conducting composite decreases at high frequency as wt% of filler increases in the composite.