Dielectric anomalies of Pb0.7La0.2TiO3-based perovskite |
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Authors: | Hwee Ping Soon John Wang |
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Affiliation: | (1) Department of Materials Science and Engineering, Faculty of Engineering, National University of Singapore, Singapore, 117576 |
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Abstract: | Dielectric transitions from normal ferroelectric to relaxor-like and then to quantum paraelectric-like behaviour were observed
by substituting 10 to 60% of Ca2+ for Pb2+ into A-site of Pb0.7La0.2TiO3 with the required stoichiometry of Pb0.7(1−x)Ca0.7x
La0.2TiO3 (PCLT). The quantum ferroelectric relation that commonly applies to SrTiO3-based perovskites, T
maxα (X − X
c
)1/2, fails to describe the observed dielectric anomalies in PCLT, whereby the transition temperature vanishes with a finite slope.
Quantum ferroelectric behaviour that exhibits a sharp dielectric peak but violates the Curie-Weiss law was not observed throughout
the composition range studied. Unlike the typical quantum paraelectric SrTiO3, the quantum paraelectric-like behaviour observed for PCLT with x = 0.55 and 0.60 exhibit negative transition temperatures, as shown by the fittings to both the Curie-Weiss and Barrett’s
relations. Thermal hysteresis was surprisingly observed in substituted PCLT with x = 0.30 and 0.40 that exhibit frequency dispersive relaxation. To establish a correlation between the dielectric anomalies
and structural parameters, analyses on global and local perovskite lattices were carried out using X-ray diffraction technique
and micro-Raman spectroscopy. |
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Keywords: | Ferroelectric Relaxor Quantum paraelectric |
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