P. Sarah

Synthesis and electrical properties of SrBi4Ti4O15 piezoelectric ceramics

Polycrystalline SrBi4Ti4O15 (SBiT) ceramics have been synthesized by a sol–gel method. These ceramics were structurally characterized by powder x-ay diffraction studies (XRD), Rietveld analyses and scanning electron microscopy (SEM). The XRD pattern of SBiT crystallized into an orthorhombic structure with A21 am as space group. The lattice parameters were calculated by Rietveld refinement. SEM images of SBiT show plate-like grains with random orientation of plate faces. Dielectric properties as a function of temperature at different frequencies are reported for this ceramic. Poling experiments were carried out to determine the piezoelectric coefficients. The conductivity of sintered ceramic was studied using impedance spectroscopy. Cole–Cole plots show the presence of two semicircular arcs, suggesting the existence of grain and grain boundary effects.

Study of Effect of Doping on Grain and Grain Boundary Parameters of Sr1−2xNaxNdxBi4Ti4O15 (x = 0−0.5) Ceramics Using Impedance Spectroscopy

Detailed impedance studies are done on Sr1−2xNaxNdxBi4Ti4O15 (x = 0, 0.1, 0.2, 0.4 and 0.5) system prepared by both sol gel and solid state method. An effort is made to explain the different mechanisms involved in the conduction mechanism through impedance studies. Grain boundary conduction dominates over the grain conduction. Capacitance is associated with the net polarization of ferroelectric domains. Grain boundaries required higher activation energies for hopping than the grains.

Modeling of dielectric behavior using modified Lorentz equation for Ca0.1Sr0.9R0.1Bi1.9Ta2O9 (R=Nd, Pr & La) ceramics

ABSTRACT Ceramic samples Ca0.1Sr0.9R0.1Bi1.9Ta2O9 (R=Nd, Pr & La) were prepared by solid state double sintering route. XRD data confirms single phase formation with orthorhombic structure at room temperature. SEM studies revealed polycrystalline nature with randomly oriented needle and plate like morphology for Nd and La doped CSBT ceramics. Dielectric studies were carried out as a function of temperature at different frequencies. Modified Lorentz equation which gives information about the thermally activated orientation of dipoles was used to describe the temperature dependence of dielectric data. The activation energy for thermally activated orientation of dipoles for the present ceramic samples was found to be in the range 60–130 μeV depending up on the type of rare earth ion substitution in CSBT.

Dielectric, Ferroelectric and Piezoelectric Properties of Sr0.8Na0.1Nd0.1Bi4Ti4O15 Prepared by Sol Gel and Solid State Technique

Effect of lower ionic radii (Na and Nd) substitution in A-site on the structure, dielectric, ferroelectric and piezoelectric properties of SrBi4Ti4O15 (SBT) is investigated in this paper. The samples are prepared by solid state double sintering method and sol gel method based on pechini process. Substitution of smaller ions reduced the dielectric constant and remanent polarization values. But sol gel samples showed good dielectric and ferroelectric properties. A-site substitution has resulted in improved Curie temperature and piezoelectric properties. As a result, Na and Nd modified SBT ceramics are found to be excellent high temperature piezoelectric materials.

Electromechanical Properties of A-Site (LiHo)-Modified Strontium Bismuth Titanate (SrBi4Ti4O15) Piezoelectric Ceramics

The Aurivillius-type bismuth layer-structure Sr0.84(LiHo)0.08Bi4Ti4O15 (SBT-LiHo) piezoelectric ceramics were synthesized using conventional solid state processing. Phase analysis was performed by X-ray diffraction (XRD). The dielectric, piezoelectric, ferroelectric, and electromechanical properties of SBT-LiHo ceramics were investigated. The piezoelectric activities were found to be significantly enhanced compared to SrBi4Ti4O15 (SBT) ceramics, which can be attributed to the lattice distortion and the presence of bismuth vacancies. The dielectric properties of SBT-LiHo ceramics at elevated temperatures were investigated in detail.

Frequency and Temperature Dependence of Electrical Properties of Zirconium and Neodymium Substituted SrBi4Ti4O15 Ceramics

Polycrystalline ceramics SrNdxBi4-xZryTi4-yO15 (x = 0.00, 0.025, 0.05, 0.075, 0.1, y = 0.00, 0.025) were prepared by using the conventional solid-state reaction method. Orthorhombic structure with single phase was identified by X-ray diffractogram (XRD). Impedance, AC and DC conductivity studies were investigated in the frequency range, 1 Hz–1 MHz and temperature range from room temperature (RT) to 600°C. From impedance data, various parameters grain (bulk) resistance (Rg) and capacitance (Cg), grain boundary resistance (Rgb) and capacitance (Cgb) were determined. Grain and grain boundary relaxation times (τg, τgb), activation energies for relaxation and conduction were evaluated as a function of temperature.

Electromechanical coupling studies on Sr1-2xNaxNdxBi4Ti4O15 compounds in free and clamped-state for transducer application

ABSTRACT Sr1-2xNaxNdxBi4Ti4O15 compounds were prepared through solid state sintering route. Capacitance & modulus resonance and anti-resonance behavior was observed for the ceramic samples studied under free and clamped-state respectively. Highest values of electromechanical coupling factor were observed for sample composition with x = 0.40 in the free-state. The values of Kt and Keff under free-state for this composition are 0.61 and 0.57 respectively. The value of d33, under free-state, for x = 0.0 and x = 0.4 compositions are higher when compared to other compositions and the values are 7.28 pm.V−1 and 7.03 pm.V−1 respectively. Ceramic samples studied under clamped-state showed electromechanical coupling above 99.6%. Among samples studied under clamped-state, ceramic composition with x = 0.5 showed the highest value of d33 when compared to other compositions with a value of 22.42 nm.V−1.

Electrical properties of sodium and neodymium modified SrBi4Ti4O15 piezoelectric ceramics

ABSTRACT Ferroelectric ceramic Sr0.8Na0.1Nd0.1Bi4Ti4O15 (SNNBT) is prepared by solid state reaction method. Single phase formation with orthorhombic structure is confirmed by X- Ray diffraction analysis. Scanning electron micrograph of the ceramic shows the plate like grains of different sizes. Dielectric properties and phase transitions are studied. Relationship of Curie temperature with ionic radii of elements is discussed. Cole-Cole plots of impedance suggest the relaxation to be non-Debye type. The activation energies are obtained in Ferro and Para electric regions from the temperature variation of dc conductivity. Piezoelectric parameters have been measured on well-densified and poled samples. This study shows that SNNBT is a proficient ceramic for applications at high temperatures.

Impedance and electromechancial studies on Ca0.1Sr0.9LaxBi2-xTa2O9 ceramics

ABSTRACT Ca0.1Sr0.9LaxBi2-xTa2O9 ceramics were synthesized through solid state double sintering route. Impedance, resonance and anti-resonance studies under clamped state were carried out on the prepared ceramics. The activation energy for relaxation is within the range 0.850–1.230 eV depending up on composition x. Equivalent circuit modelling was done to the experimental Cole-Cole data so as to obtain the grain, grain boundary resistance and capacitance. The activation energy for grain conduction increased with the increase of x value except for x = 0.05 ceramic composition. The activation energy for grain boundary conduction is lower for the ceramic compositions with lanthanum doped when compared to pure CSBT ceramic. The activation energy for grain and grain boundary conduction are within the range 0.748–1.338 eV depending up on composition x and temperature. The electromechanical coupling factors are above 0.9990 and vary in fourth decimal place with the increase of temperature and composition x. The electromechanical coupling factor decreased with the increase of x value.

Synthesis, Characterization and Electrical Properties of La Modified SrBi4Ti3.975Zr0.025O15

Ceramic samples of composition Sr(Bi4-xLax)(Ti3.975Zr0.025)O15 (x = 0.025, 0.05 ,0.075 and 0.1) is prepared by solid-state method. It is characterized by X-ray diffraction (XRD), scanning electron micrograph (SEM) and energy dispersive spectra (EDS). From XRD and SEM analysis, single-phase formation is identified with orthorhombic structure and particle size is calculated. Compositions are confirmed from EDS. Electrical properties are studied by impedance spectroscopy and conductivity. From impedance, AC and DC conductivities are recorded in the temperature range room temperature (RT) – 600°C. From impedance data, various parameters like bulk resistance or grain resistance (Rb or Rg), bulk capacitance or grain capacitance (Cb or Cg), grain boundary resistance (Rgb), and grain boundary capacitance (Cgb) are determined. Grain and grain boundary relaxation times (τg, τgb) are also evaluated as a function of temperature. From AC and DC conductivity plots activation energies for conduction are obtained. Results obtained lead to improved understanding of conductivity of samples.