Publication: Synthesis and dielectric properties of bismuth titanate and neodymium doped bismuth titanate
Date
2009-05-01
Authors
Ahmad Shuhaini, Ahmad Ehsan
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Abstract
Bismuth titanate (BIT) and bismuth neodymium titanate (Bi4-xNdxTi3O12 where x=0.2, 0.4, 0.6, 0.8, 1.0) powders were synthesised via combustion method for dielectric antenna application. In order to obtain highly pure BIT and BNdT powders, the effect of bismuth and titanium addition were investigated. The as synthesised powders were calcined at 800°C for 3 hours. The addition of 5% titanium produced a highly pure BIT with orthorhombic structure. The characteristics of BIT and BNdT such as crystal structure were characterized by X-ray diffraction (XRD). Crystallite sizes were determined from X- ray line broadening using Scherrer’s equation. Calcined powders are pressed into pellet form and sintered at temperatures of 1050°C and 1100°C. Effect of sintering temperature on the phase transformation and microstructure of BIT and BNdT was investigated. Higher temperature and soaking time produce high c-axis oriented grains. SEM micrographs of BIT shows equiaxed grains while increasing Nd content produces plate-like and rod-like grains. The electrical properties were studied using an impedance analyzer. The grain orientation and density influence the relative permittivity of the pellets. BNdT pellets show high relative permittivity and low dielectric loss as compared to BIT. The highest relative permittivity was obtained from BNdT (x=0.4) pellet sintered at 1100°C for 3 hours which is 276. However, the dielectric loss for this pellet is 0.058. This could be due to the presence of porosity and moisture.