Effect of porosity on the ferroelectric and piezoelectric properties of (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 piezoelectric ceramics (original) (raw)
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Structural, electrical, and light up conversion properties of Erbium (Er) substituted bismuth titanate (Bi 4 À x Er x Ti 3 O 12 ) ceramics have been investigated. Formation of single phase Bi 4 Ti 3 O 12 with orthorhombic unit cell is confirmed, and orthorhombic distortion is found to decrease with increasing erbium content (x). Presence of Bi 2 Ti 4 O 11 secondary phase ( o5 wt%) is detected due to bismuth loss, and is found to decrease with increasing erbium content (x). A randomly oriented plate like microstructure with increasing grain size is found to change abruptly at higher erbium content x 4 0.2. Raman spectroscopy reveals that (Bi 2 O 2 ) 2 þ layers remain unaffected in the modified compositions, and Er 3 þ substitution for Bi 3 þ occurs predominantly at the A-site in the perovskite blocks leading to cationic disorder and a decrease in the TiO 6 octahedral distortion. Increasing Er substitution results in reduced dielectric losses and reduced dispersion in ε 0 and tan δ over a wide frequency range (10 À 2 to 10 6 Hz). Strong UC luminescence at 527, 548 and 662 nm is seen under an excitation of 980 nm for an optimum erbium content (x ¼0.2) and is attributed to the transitions 2 H 11/2 -4 I 15/2 , 4 S 3/2 -4 I 15/2 and 4 F 9/2 -4 I 15/2 respectively. Increasing Er content (x 4 0.2) exhibits pronounced luminescence quenching due to cross-relaxation (CR) process, and degrades the ferroelectric properties. However the electrical conductivity, dielectric losses and dielectric dispersion reduce considerably with increasing Er content up to x ¼0.3.
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BaTi 0.9 Zr 0.1 O 3 (BZT), Ba 1Àx Ln 2x/3 h x/3 Ti 0.9 Zr 0.1 O 3 (with x = 0.5% mol and Ln = Er) (BZT-Er) and Ba 1Àx Ln 2x/3 h x/3 Ti 0.9 Zr 0.1 O 3 (with x = 0.5% mol and Ln = Pr) (BZT-Pr) were prepared via the conventional solid-state reaction method. X-ray diffraction showed that all these ceramics were in the single perovskite phase at room temperature (RT). The temperature dependence of dielectric behavior was investigated in the temperature range 25-225°C and exhibited a classical ferroelectric behavior. A slight decrease of the Curie temperature (T C) with Pr 3+ and Er 3+ substitution was observed in addition to an increase in the maximum dielectric permittivity (e 0 r max) of about 40% for the BZT-Er. At RT, the ferroelectric and piezoelectric coefficients were decreased for BZT-Pr, but were maintained for BZT-Er with a piezoelectric coefficient (d 33) of 185 pC/N, a planar electromechanical coupling factor of 30%, and a remanent polarization of 11.6 lC/cm 2. The Raman bands as a function of temperature confirmed the paraelectric-ferroelectric phase transition of all those ceramics. The photoluminescence spectra showed that strong red (615 nm and 645 nm) and bright green (523 nm and 545 nm) emission bands were obtained, under excitation by laser at 488 nm at RT, for BZT-Pr and BZT-Er, respectively. These multifunctional materials showed a significant technological promise in coupling device applications.
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Solid State Sciences, 2009
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Pellet samples of (Ba1-xCaxZr1-yTiy)O3 (x = 0.150, y = 0.90) were prepared using the solid-state reaction method following double sintering. The electrical and optical properties of (Ba1-xCaxZr1-yTiy)O3 (x = 0.150, y = 0.90) ceramics were studied. For Ba0.85Ca0.15Zr0. 1Ti0.9)O3 ferroelectric perovskite ceramics, the dielectric and structural properties were explored. The prepared composition of BCZT ceramics were calcined at 1100 oC. The sintering temperature was 1300 oC. Dielectric properties were observed from room temperature (RT) to 150 oC, at 1 MHz. The powder of the sintered samples has been taken for reflectance measurement at UV-Vis range. From the observed tauc plot, the band-gap is calculated. The measured band- gap is 3.19 eV.
Structure and ferroelectric studies of (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 piezoelectric ceramics
Materials Research Bulletin, 2013
For the past few decades, Pb-based perovskite ferroelectrics such as Pb(Zr,Ti)O 3 (PZT) and Pb(MgNb)O 3 (PMN) have been studied extensively as potential technological materials in view of their excellent piezoelectric properties . However, in view of Pb toxicity the search has been started to find suitable lead-free materials that have piezoelectric properties comparable to archtypical Pb compounds, PZT and PMN. In this context, Na 0.5 Bi 0.5 TiO 3 (NBT) and its solid solutions with BaTiO 3 [4], K 0.5 Bi 0.5 TiO 3 [5], (K 0.5 ,Na 0.5 )NbO 3 [6] have been studied. Strong piezoelectricity of PZT and PMN materials is believed to result from the coexistence of two phases and the composition driven phase transition between the two ferroelectric phases (morphotropic phase boundary, MPB). On the other hand, lead-free compounds with MPB exhibited significantly improved piezoelectric properties, albeit inferior to the lead-based ones. Recently, Liu et al. [7] reported large piezoelectric properties in 0.5[Ba(Zr 0.2 Ti 0.8 )O 3 ]-0.5[(Ba 0.7 Ca 0.3 )O 3 ] (BZT-BCT) ceramic with a d 33 $ 600 pC/N, higher than in PZT, and with a tricritical point (TCP) near room temperature. Enhancement of the piezoelectric properties in BZT-BCT has been achieved due to the existence of MPB near room temperature, with a triple point of paraelectric cubic (C), ferroelectric rhombohedral (R) and tetragonal (T) phases. This triple point leads to an anisotropically flattened energy profile so that the polarization can easily be rotated between h1 1 1i R and h0 0 1i T states by external stress or electric field .
Materials
The present paper reports the dependence of dielectric, ferroelectric and piezoelectric properties on the porosity level in BaZr0.15Ti0.85O3 ceramics with porosity from 5% to 21%. Microporosity with 0–3 connectivity has been produced using PMMA microspheres as a sacrificial template. The functional properties (dielectric, ferroelectric and piezoelectric effect) are mostly affected by the “dilution effect”: permittivity decreases by 40% when porosity increases by 21%, and Pmax decreases from 13 to 5 µC/cm2 while the Prem is in the range of (2–8) µC/cm2. However, the reduction of the zero-field permittivity and hysteretic behaviour of ε(E) while the tunability level is still high makes from porous ceramics interesting materials for tunability application.
Journal of Materials Science: Materials in Electronics
Ferroelectric ceramics (Ba 0.85 Ca 0.15)(Ti 0.9 Zr 0.1-x Sn x)O 3 (x=0.00, 0.02, 0.04, 0.06) were prepared by a sol-gel method. Structural investigation revealed the coexistence of tetragonal (P4mm) and orthorhombic (Pmm2) symmetries at room temperature for the undoped ceramic, while only a tetragonal structure (P4mm) was observed for the doped ceramics. Dielectric measurements indicate a dielectric relaxation process at high temperatures which is essentially related to the hopping of oxygen vacancies. Furthermore, a down shifting of the Curie temperature (T C) with increasing Sn 4+ doping rate has been revealed. The temperature profiles of the Raman spectra unveiled the existence of polar nanoregions (PNRs) above the Curie temperature in all ceramics. The ferroelectric properties were found to be related to the microstructure. Electrocaloric effect was investigated in this system that revealed an electrocaloric responsivity of 0.225 10-6 K m/V for the composition with x = 0.04 Sn doping, where other remarkable physical properties were also observed.