Structural, Dielectric and Pyroelectric properties of Lanthanum modified Lead Titanate Thin Films
- PDF / 772,820 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 108 Downloads / 253 Views
D3.33.1
Structural, Dielectric and Pyroelectric properties of Lanthanum modified Lead Titanate Thin Films Sonalee Chopra**, Seema Sharma, T.C.Goel* and R.G.Mendirattaa Advanced Ceramics Laboratory, Department of Physics, Indian Institute of Technology, New Delhi-110016, India a Netaji Subhas Institute of Technology, Dwarka, New Delhi-110 045, India ABSTRACT Ferroelectric lead lanthanum titanate (Pb1-xLaxTi1-x/4O3) (PLTx) thin films (x=0.04,0.08 and 0.12) have been prepared by sol-gel spin coating process on ITO coated 7059 Corning glass substrates. Investigations have been made on the crystal structure, surface morphology, dielectric and ferroelectric properties of the thin films. For a better understanding of the crystallization mechanism, the structural investigations were carried out at various annealing temperatures (350°C, 450°C, 550°C and 650°C). Characterization of these films by X-ray diffraction shows that the films annealed at 650°C exhibit tetragonal structure with perovskite phase. Replacement of lanthanum in lead titanate results in reduction of tetragonal ratio (c/a), resulting in better mechanical stability. Microstructural analysis of the films are carried out by taking the Atomic Force Microscope (AFM) pictures. AFM images are characterized by slight surface roughness with a uniform crack free, densely packed structure. Dielectric, pyroelectric and ferroelectric studies carried out on these films have been reported. Dielectric constant and pyroelectric coefficient increase while Curie temperature decreases with increase in La content. The pyroelectric figures of merit of the films have also been calculated which suggest that 8% lanthanum is best suited material for pyroelectric detectors owing to its high pyroelectric coefficient (~ 29nC/cm2 K), high voltage responsivity (~420Vcm2/J), high detectivity (~1.04x105 Pa-1/2) and low variation of pyrocoefficient with temperature. INTRODUCTION Ferroelectric thin films are being studied with great interest because of their possible use in various integrated electronic devices. Lead titanate (PT) modified by rare earth elements and alkaline earth elements have emerged as high promising materials for several piezo-electric applications due to existence of large electro-mechanical anisotropy in the coupling factors [1]. Several dopants have been employed and very encouraging results have boosted the research activity in the modified PT thin films. The incorporation of off-valent (La3+, Sm3+, Nd3+, GD3+) and isovalent ions (Ca2+,BA2+, Sr2+) into PT ceramics is reported to enhance the mechanical stability along with good dielectric and ferroelectric properties [2]. The substitution of these ions *E
-mail : [email protected],
** E
-mail : [email protected]
D3.33.2
results in the reduction of lattice anisotropy leading to hard and dense ceramics with high mechanical strength [3-5]. Recently, lanthanum modified lead titanate (PLT) thin films have been studied for their possible use in optical waveguides, dynamic random access memories, non volatile
Data Loading...
