Dielectric and Impedance Studies on New Bismuth Layered Compound SrBi₃NbTi₂O₁₂

In a comprehensive study of bismuth compounds, Aurivillius has synthesized a number of mixed bismuth oxides of the formula (Bi ₂ O ₂ ) ^{2 +} (M _{x − 1}R _x O _{3x + 1} ) ^{2 −} . Here M can be mono-, di-, or trivalent ions or a mixture of them, R represent Ti ^{4 +} , Nb ^{5 +} , Ta ^{5 +} etc and x can have values of 2, 3, 4, etc. Bismuth Titanate (Bi ₄ Ti ₃ O ₁₂ ), is an example of such compounds with x = 3. Modified Bismuth Titanate Ceramics were prepared by using solid state technique with Strontium and Niobium substitution at M and R sites respectively. The dielectric measurements were made from room temperature to 550°C. In the present investigation dielectric maximum is observed at around 350°C. Usually dielectric maximum for Bismuth Titanate occurs at 675°C. The impedance spectroscopy is used to study the relaxation behavior of the sample in view of low T _C and low loss. The impedance and electric modulus are studied at different constant temperatures ranging from RT to 550°C,over a frequency range of 100 Hz to 1 MHz. The results obtained in dielectric and impedance studies are presented.

Keywords:

• BLSF materials
• dielectric and impedance properties
• Sr and Nb doped BIT

Acknowledgments

We thank G. Swaminathan, BHEL (R&D) Vikas nagar, Hyderabad for extending XRD facility.

Paper originally presented at AMF-4, Bangalore, India, December 12–15, 2003