Origin of the crossover between a freezing and a structural transition at low concentration in the relaxor ferroelectric K1-xLixTaO3
- Lehigh Univ., Bethlehem, PA (United States)
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States)
The origin of the relaxor behavior in K1-xLixTaO3 (KLT) and other disordered perovskites is now recognized to be due to the reorientation of the polar nanodomains formed by the correlated dipoles of off-center ions. The collective dynamics of these systems evolve through several temperature stages. On decreasing temperature below the so-called Burns temperature TB, individual dipoles become correlated within nanosized regions. On further cooling, the slow dynamics of these polar regions allows local lattice distortions to take place and the formation of polar nanodomains at T* < TB. At still lower temperature, some relaxors undergo a phase transition while others do not. In KLT, there is a critical Li concentration xc = 0.022 above which the system undergoes a structural transition at Tc, and below which it freezes in a dipole glass state at Tf. To better understand the nature of this critical concentration, the changes that occur upon crossing it and the nature of the dipole glass state, the collective dynamics of KLT have been studied by dielectric spectroscopy and neutron diffraction for two Li concentrations (x = 0.026 and 0.018), close to but straddling the critical concentration xc. Two very different transitional behaviors are observed. Just below this critical concentration, KLT displays critical slowing down and the onset of freezing as seen in hydrogen-bonded molecular ferroelectrics, while just above this concentration, KLT undergoes a first-order structural transition.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- AC05-00OR22725
- OSTI ID:
- 1265469
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 91, Issue 13; ISSN 1098-0121
- Publisher:
- American Physical Society (APS)
- Country of Publication:
- United States
- Language:
- English
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