Pressure-induced electrical and structural anomalies in Pb_1−xCa_xTiO₃thin films grown at various oxygen pressures by chemical solution route

Abstract

Lead calcium titanate (Pb1−xCaxTiO3 or PCT) thin films have been thermally treated under different oxygen pressures, 10, 40 and 80 bar, by using the so-called chemical solution deposition method. The structural, morphological, dielectric and ferroelectric properties were characterized by x-ray diffraction, FT-infrared and Raman spectroscopy, atomic force microscopy and polarization–electric-field hysteresis loop measurements. By annealing at a controlled pressure of around 10 and 40 bar, well-crystallized PCT thin films were successfully prepared. For the sample submitted to 80 bar, the x-ray diffraction, Fourier transformed-infrared and Raman data indicated deviation from the tetragonal symmetry. The most interesting feature in the Raman spectra is the occurrence of intense vibrational modes at frequencies of around 747 and 820 cm−1, whose presence depends strongly on the amount of the pyrochlore phase. In addition, the Raman spectrum indicates the presence of symmetry-breaking disorder, which would be expected for an amorphous (disorder) and mixed pyrochlore–perovskite phase. During the high-pressure annealing process, the crystallinity and the grain size of the annealed film decreased. This process effectively suppressed both the dielectric and ferroelectric behaviour. Ferroelectric hysteresis loop measurements performed on these PCT films exhibited a clear decrease in the remanent polarization with increasing oxygen pressure.

Analysis of the Pb0.30CaxSryTiO3 ternary system: The effect of Ca2+ and Sr2+ cations on the electrical properties of PbTiO3

“…Aiming at controlling the ferroelectric properties, the coupling between the properties of the PT, CaTiO3 (CT) and SrTiO3 (ST) perovskites opens new possibilities for data storage in DRAM's or FeRAM's elements, which can be prepared to maximize the memory capacity in a small volume. There are several publications that bring different combinations of PT, CT and ST perovskites, resulting systems as: Pb0.90Ca0.10TiO3 (F. Pontes et al, 2008), Pb0.60Ca0.20Sr0.20TiO3, Pb0.50Ca0.25Sr0.25TiO3 and Pb0.40Ca0.30Sr0.30TiO3 (D. Pontes et al, 2014), Pb0.60Sr0.40TiO3 (Leal et al, 2004, Pb0.74Ca0.26TiO3 (Capeli et al, 2017), Pb0.76Ca0.24TiO3 (D. Pontes et al, 2001ab), and Pb0.50Sr0.50TiO3 (F. Pontes et al, 2005).…”

Synthesis and characterization of nanostructured (Pb1−xSrx)TiO3thin films by a modified chemical route

“…Doping with different perovskites, such as CaTiO 3 [1], ZrTiO 3 [2] and SrTiO 3 [3], on A and B sites gives excellent electric, ferroelectric, piezoelectric and optical properties [4][5][6]. The main focus of earlier studies on (Pb, Sr)TiO 3 (PST) thin films was on the field of highly tunable device applications.…”