Evaluating the polymorphic phase transition in calcium-doped Ba(Zr_0.05Ti_0.95)O₃: a lead-free piezoelectric ceramic

Abstract

Structural and dielectric investigations were carried out on a perovskite lead‐free (Ba1−xCax)(Zr0.05Ti0.95)O3 ferroelectric ceramic for x = 0.03, 0.05, 0.08, 0.10, 0.12 and 0.15. The room‐temperature structural analysis reveals a crossover from orthorhombic to tetragonal crystal structure near x = 0.10. A coexistence of tetragonal (P4mm) and orthorhombic (Pmm2) structure is observed in the composition range 0.05 ≤x≤ 0.10. The fraction of tetragonal phase increases from 27% for x = 0.05 to 71% for x = 0.10. The dielectric measurements show that the tetragonal to orthorhombic and rhombohedral to orthorhombic transition temperatures decrease with an increase in Ca2+ content, while the cubic to tetragonal transition temperature remains the same. It is also shown that for the tetragonal to orthorhombic transition a phase coexistence occurs over a temperature range of about 18 K. The coexistence range covers room temperature for intermediate compositions: x = 0.05, 0.08 and 0.10. Therefore, higher dielectric and piezoelectric properties are observed in these compositions.

Structural perspective on the anomalous weak-field piezoelectric response at the polymorphic phase boundaries of (Ba,Ca)(Ti,M)O3Abebe1, Brajesh2, Mishra3 et al. 2017Phys. Rev. B291180View full textAdd to dashboardCite

“…Qualitatively, this phase diagram is similar to that of BCTS (Fig. 6a), with the three phase boundaries Pm3m-P4mm, P4mm-Amm2 and Amm2-R3m merging at ~ 11 mole percent of Sn at ~ 45 o C. As per this phase diagram, and also reported earlier [20,37,38], the P4mm-Amm2 and Amm2-R3m boundaries at room temperature are at y = 0.05 and y = 0.08, respectively. Amm2 phase is stable in the shown in Fig.…”

A Correlation between Structural Parameters and Electrical Conductivity of Calcium‐Modified Ba(Zr0.05Ti0.95)O3 Ceramic

“…The movement of “ t ” toward 1.00 with calcium content indicates a gradual transformation toward higher symmetry with calcium content. These results are in concurrence with our XRD studies, which revealed a crossover from lower symmetry orthorhombic structure to higher symmetry tetragonal crystal structure [ 43 ] with increase in calcium content. The (% N ) number of equivalent oxygen sites (in percentage) for different calcium content “ x ” values in BCZT compound was calculated as 1/( t − 1) and is represented in Figure 14 .…”

Phase Diagram and Enhanced Piezoelectric Response of Lead‐Free BaTiO3–CaTiO3–BaHfO3 System

“…4,20,21 The compositions own a polymorphic phase transition (PPT) similar to the phase transitions of the BT. For electrical measurements, silver paste was coated on both sides of the samples as the electrodes, and the samples were fired at 550°C for 30 min.…”

“…be considered as T R-O , T O-T , and Curie temperature T C , respectively because of their phase transition similar to those of BCZT. 4,20,21 The compositions own a polymorphic phase transition (PPT) similar to the phase transitions of the BT. It is found that the T C gradually shifts to a higher temperature, while the T R-O and T O-T go downward with increasing x.…”