Raman studies between 11 and 300 K of the effects of Nd additive in ferroelectric lead-titanate ceramics
- Microelectronics and Material Physics Laboratories, University of Oulu, P.O. Box 400, 90571 Oulu (Finland)
Low-temperature Raman spectroscopy between 11 K and room temperature was used together with room-temperature x-ray-diffraction experiments for a study of the effects of Nd additive in ferroelectric lead-titanate ceramics. Raman spectra were measured between 40 and 1200 cm{sup {minus}1} at different low temperatures from ceramic Pb{sub 1{minus}3{ital y}/2}Nd{sub {ital y}}TiO{sub 3} samples with Nd concentration {ital y} between 0 and 10{percent}. Nd addition was found to decrease strongly the tetragonal strain ({ital c}/{ital a} ratio at room temperature decreased from 1.064 to 1.034 in the Nd concentration range {ital y} from 0 to 10{percent}) and unit-cell volume (2.0{percent} shrinkage at {ital y}=10{percent}) of ferroelectric lead titanate. A frequency decrease of all transverse Raman modes, except the {ital E}(3TO) mode, followed the decrease of the tetragonal strain with Nd addition. A quadratic extrapolation of the frequency behavior of {ital E}(1TO) and {ital A}{sub 1}(1TO) modes with Nd concentration {ital y} interpreted that the modes become unstable at around {ital y}=30{percent}. Our results revealed a subpeak structure for {ital A}{sub 1}(1TO)-mode frequencies in agreement with earlier findings [Foster {ital et} {ital al}., Phys. Rev. B {bold 48}, 10160 (1993)]. Nd addition had a strong effect on the relative intensities between different subpeaks. It was also possible to find, on the basis of some earlier computational results, an anharmonic double-well potential energy for {ital A}{sub 1}(1TO)-mode vibrations to fit approximately the observed subpeak frequencies. Some extra unknown Raman peaks were also found to increase with increasing Nd concentration and decreasing temperature. {copyright} {ital 1996 The American Physical Society.}
- OSTI ID:
- 396617
- Journal Information:
- Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 17 Vol. 54; ISSN PRBMDO; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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