Thermal analysis of phase transitions in PbZr1−xSnxO3 antiferroelectric single crystals

Statistical Inference for Stochastic Processes, Dec 2016

The combined thermal analysis techniques thermal expansion: and differential scanning calorimetry were used to characterize various phase transitions that exist in the solid solutions of PbZr1−xSnxO3. Using thermodynamic quantities, i.e., thermal expansion and specific heat to distinguish first-order transitions from second-order ones, we demonstrate that some perovskite antiferroelectrics can exhibit continuous transition at their Curie temperature T C. We observed such a transition in antiferroelectric crystals of solid solutions based on PbZrO3. Although pure PbZrO3 is a classical example of antiferroelectric crystal with a first-order transition at T C, the solid solutions of PbZr1−xSnxO3 in the range of composition of x > 0.25 seem to exhibit a second-order phase transition.

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Thermal analysis of phase transitions in PbZr1−xSnxO3 antiferroelectric single crystals

J Therm Anal Calorim Thermal analysis of phase transitions in PbZr12xSnxO3 antiferroelectric single crystals Irena Jankowska-Sumara 0 1 2 3 Jan Z_ ukrowski 0 1 2 3 Maria Podgo´rna 0 1 2 3 Andrzej Majchrowski 0 1 2 3 0 Institute of Applied Physics, Military University of Technology , ul. Kaliskiego 2, Warsaw , Poland 1 Institute of Physics, Pedagogical University of Cracow , ul. Podchora ̨ z_ych 2, Krako ́w , Poland 2 & Irena Jankowska-Sumara 3 Academic Center for Materials and Nanotechnology, AGH University of Science and Technology , Av. A. Mickiewicza 30, 30-059 Krako ́w , Poland The combined thermal analysis techniques thermal expansion: and differential scanning calorimetry were used to characterize various phase transitions that exist in the solid solutions of PbZr1-xSnxO3. Using thermodynamic quantities, i.e., thermal expansion and specific heat to distinguish first-order transitions from second-order ones, we demonstrate that some perovskite antiferroelectrics can exhibit continuous transition at their Curie temperature TC. We observed such a transition in antiferroelectric crystals of solid solutions based on PbZrO3. Although pure PbZrO3 is a classical example of antiferroelectric crystal with a first-order transition at TC, the solid solutions of PbZr1-xSnxO3 in the range of composition of x [ 0.25 seem to exhibit a second-order phase transition. Antiferroelectrics; Phase transitions; Specific heat; Thermal expansion Introduction PbZr1-xSnxO3 (PZS) belongs to the family of AB0B00O3 perovskite solid solutions based on well-known antiferroelectric material PbZrO3. Phase diagram showing different phases that exist in PZS with 0 \ x \ 0.4 obtained on the basis of dielectric, optic and thermodynamic measurements was already reported [ 1 ]. The substitution of Sn4? ions at the Zr4? sites in PZS single crystals does not alter the basic structure of PbZrO3 which crystallizes in an orthorhombic structure at room temperature RT. The stability and range of the existence of subsequent phases, namely A1 (orthorhombic)–A2 (orthorhombic)–IM (multiple cell cubic)–PE (cubic), depend strictly on the composition. Such rich phase diagram of PZS compound and its potential possibilities of applications (especially the PZS compounds enriched with Ti ions) have attracted the interest of many researchers [ 2–5 ]. It was found that mechanism of the A1–A2 phase transition is of purely displacive character for all investigated compositions [6]. In a case of phase transition at TC, above x = 0.2 a gradual change from order–disorder to displacive character also takes place. Despite the efforts made, the nature of phase transitions is still not clear. Numerous experiments revealed distinct differences in physical properties of single crystals with compositions of x below and above 0.25. It is believed that all of this is due to the so-called tricritical point, the existence of which was postulated in early studies [ 7 ]. It means that around this concentration, the change from the first- to second-order phase transition at TC takes place. Simultaneously, the large value of the dielectric permittivity at TC which is observed in both PbZrO3 and PbZr1-xSnxO3 single crystals with x \ 0.25 considerably decreases in the compositions with x [ 0.25 and another intermediate phase—IM, called also ‘‘multiple cell cubic’’ [ 5 ]— appears. In our earlier studies of specific heat [ 7 ], we found that above the value of x = 0.25, the latent heat at TC at PE–IM phase transition is absent suggesting the change of the character of the phase transition to a second order in these crystals. However, in this paper, IM phase was erroneously identified as ferroelectric one. In later studies, we found that this intermediate phase is ferroelastic one [ 1 ]. Later, Brillouin scattering measurements made in PbZr0.72Sn0.28O3 pointed to enhanced fluctuations in coupling between local polarization and strain which occurs due to Sn replacing in Zr-site [ 8 ]. Such large fluctuations of order parameter are expected near the secondorder phase transition, and electrostrictive coupling between the strain and fluctuations of local polar regions seems to be the origin of the anomalous behavior of the temperature dependence of the relaxation time of this polar regions—sLA [ 8 ]. Since all previous studies do not definitely prove that second-order phase transition can exist in perovskite materials with antiferroelectric phase transition, we undertook a detailed study to be able to unequivocally confirm the suggestion. For the purposes of this study newly acquired high quality, transparent crystals were selected for the experiment. Three crystals with values of x chosen from different points of the phase diagram were selected, namely 0.04, 0.09 and 0.3. The stoichiometry of the compounds and thus quality of the crystals were verified with X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDS). Additionally, the Mo¨ssb (...truncated)


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Irena Jankowska-Sumara, Maria Podgórna, Andrzej Majchrowski, Jan Żukrowski. Thermal analysis of phase transitions in PbZr1−xSnxO3 antiferroelectric single crystals, Statistical Inference for Stochastic Processes, 2017, pp. 713-719, Volume 128, Issue 2, DOI: 10.1007/s10973-016-6001-x