RELAXOR FERROELECTRICS

MICROWAVE LABORATORY

DEPARTMENT OF PHYSICS, IIT MADRAS, CHENNAI - 600 036

Dr. V. Subramanian Email: manianvs(at)iitm.ac.in

Associate Professor

RELAXOR FERROELECTRICS

Difference between normal ferroelectrics and relaxor ferroelectrics:

Normal Ferroelectric	Relaxors
Well defined PE hysterisis	Slim loop in PE
Sharp phase transition	Diffused
Tc does not vary with frequency	Temperature at which the dielectric constant is maximum shifts to higher temperature with increase in freqeuncy

Physics of relaxors

The main reason is attributed to – Polar Micro Regions

Formation of the PMR due to the dipolar defects arising out of compositional disorder.

The compositional disorder does not allow for long range ordering.

PMRs can vary in size – may follow distribution

At high temp. – large no. of smaller volume PMRs are available.

As temp. decreases, the average size of PMR increases.

Lead magnesium niobate

Lead barium zinc niobate

List of materials developed

PMN - Pb(Mg_1/3Nb_2/3)O₃

PBZN - (Ba_xPb_1-x)(Zn_1/3Nb_2/3)O₃

PSZN - (Sr_xPb_1-x)(Zn_1/3Nb_2/3)O₃

PBYN - (Ba_xPb_1-x)(Yb_0.5Nb_0.5)O₃

PBYT - Pb_1-xBa_x(Yb_1/2Ta_1/2)O₃

PFN - Pb(Fe_1/2Nb_1/2)O₃

PFT - Pb(Fe_1/2Ta_1/2)O₃

PFYT - (1-x)Pb(Yb_1/2Ta_1/2)O₃-xPb(Fe_1/2Ta_1/2)O₃

LPBZN

LPBYT

PST

NBT

List of publications related to Relaxors and diffused phase transition materials

Microwave dielectric properties of (Pb(Mg_1/3Nb_2/3)O₃ relaxor ferroelectrics
J. Venkatesh, V. Subramanian and V. R. K. Murthy
Indian J. Phys., 75A(4), 339 - 342, 2001.

Low frequency dielectric study of Barium and Strontium substituted Pb(Zn_1/3Nb_2/3)O₃ ceramics
R. R. Vedantam, V. Subramanian, V. Sivasubramanian and V. R. K. Murthy
Jap. J. Appl. Phys., 42, 7392-7396, 2003.

Low frequency dielectric studies on Pb(Fe_1/2Nb_1/2)O₃
R. R. Vedantam, V. Subramanian, V. Sivasubramanian and V. R. K. Murthy
Materials Science and Engineering B, 113, 136-142, 2004.

Dielectric study of the phase transitions in Pb_1-xBa_x(Yb_1/2Ta_1/2)O₃ ceramics
Dibyaranjan Rout, V. Subramanian, K. Hariharan, V. Sivasubramanian and V. R. K. Murthy
Ferroelectrics, 300, 67-78, 2004.

Dielectric and Raman studies in (Ba_xPb_1-x)(Yb_0.5Nb_0.5)O₃
R. R. Vedantam, V. Subramanian, V. Sivasubramanian and V. R. K. Murthy
J. Physics: Condensed Matter, 17, 361-372, 2005.

Post-sintering annealing effect on the diffuse phase transition in (Pb_1-xBa_x)(Yb_0.5Ta_0.5)O₃

Dibyaranjan Rout, V. Subramanian, K. Hariharan, V. Sivasubramanian and V. R. K. Murthy

Journal of Physics and Chemistry of Solids, 66, 809-816, 2005.

Microstructure and dielectric properties of (1-x)Pb(Yb_1/2Ta_1/2)O₃-xPb(Fe_1/2Ta_1/2)O₃, 0<x<0.2 solid solution ceramics

Dibyaranjan Rout, V. Subramanian, K. Hariharan and V. Sivasubramanian

Materials Science and Engineering B, 123, 107 – 114, 2005.

Raman spectroscopic study of (Pb_1-x Ba_x)(Yb_1/2 Ta_1/2)O₃ ceramics

Dibyaranjan Rout, V. Subramanian, K. Hariharan, V. Sivasubramanian and V.R.K.Murthy

Journal of Applied Physics, 98, 103503, 2006.

Investigation of Dielectric Properties and Glassy Behavior in Lead Barium Ytterbium Tantalate Relaxors.

Dibyaranjan Rout, V. Subramanian, K. Hariharan and V. Sivasubramanian

Journal of Physics Chemistry of Solids, Accepted for publication (2006).

Diffuse phase transition of Fe doped lead ytterbium tantalate ceramics

Dibyaranjan Rout, V. Subramanian, K. Hariharan and V. Sivasubramanian

Solid State Communication, 137, 446-450, 2006.

Thesis of Dr. (Ms.) Radha Ramani and Dr. Dibyaranjan Rout