Clamping effect on the piezoelectric responses of screen-printed low temperature PZT/Polymer films on flexible substrates

This paper introduces a new flexible lead zirconate titanate (PZT)/polymer composite material that can be screen-printed onto fabrics and flexible substrates, and investigates the clamping effect of these substrates on the characterization of the piezoelectric material. Experimental results showed that the optimum blend of PZT/polymer binder with a weight ratio of 12:1 provides a dielectric constant of 146. The measured value of the piezoelectric coefficient d33 was found to depend on the substrate used. Measured d33clp values of 70, 40, 36 pC N−1 were obtained from the optimum formulation printed on Polyester–cotton with an interface layer, Kapton and alumina substrates, respectively. The variation in the measured d33clp values occurs because of the effect of the mechanical boundary conditions of the substrate. The piezoelectric film is mechanically bonded to the surface of the substrate and this constrains the film in the plane of the substrate (the 1-direction). This constraint means that the perpendicular forces (applied in the 3-direction) used to measure d33 introduce a strain in the 1-direction that produces a charge of the opposite polarity to that induced by the d33 effect. This is due to the negative sign of the d31 coefficient and has the effect of reducing the measured d33 value. Theoretical and experimental investigations confirm a reduction of 13%, 50% and 55% in the estimated freestanding d33fs values (80 pC N−1) on Polyester–cotton, Kapton and alumina substrates, respectively. These results demonstrate the effect of the boundary conditions of the substrate/PZT interface on the piezoelectric response of the PZT/polymer film and in particular the reduced effect of fabric substrates due to their lowered stiffness

Electrical and Magnetic Studies on SrBi5FeTi4O18SrBi_5FeTi_4O_{18}

The compound $SrBi_5FeTi_4O_18$ is a five-layered material belonging to the family of Bismuth Layer Structured Ferroelectrics. Samples were prepared by the ceramic route and dc conductivity measurements were performed from room temperature to 550°C and the activation energies were calculated. Impedance and modulus spectroscopy were used as tools to analyse the sample's behavior as a function of frequency. Relaxations in the sample were noted. Magnetization measurements were performed from 80 K to 300 K. The results of the electrical and magnetic studies are presented

The dielectric and electrical properties of four layered LaBi4FeTi3O15LaBi_4 FeTi_3 O_{15}

A four layered compound LaBi/sub 4/FeTi/sub 3/O/sub 15/ has been synthesised by the ceramic route. Polycrystalline samples were prepared by uniaxial pressing and cold isostatic pressing with a view to study the effect of different compaction techniques on the physical properties of the compound. The lattice parameters were evaluated and the compound was found to have an orthorhombic symmetry. A.C. impedance techniques have been used to characterise the material. The impedance response, the bulk dielectric constant and the ferroelectric transition temperatures are presented. The transitions observed in both cases were of a diffusive type. The dielectric data is interpreted vis-a-vis the crystal chemistry of analogous bismuth layer-structured ferroelectrics

Magnetic and Magnetoelectric Studies in Polycrystalline LaBi4FeTi3O15

LaBi4FeTi3O15 is a 4-layered ferroelectromagnetic material belonging to the Aurivillius' family of compounds having an orthorhombic distortion. Polycrystalline samples of this compound were prepared by uniaxial pressing and cold isostatic pressing with a view to study the effect of different compaction techniques and its impact on the physical properties. The scanning electron micrographs of the samples showed differences in microstructures. Magnetization measurements were carried out from 80 K to room temperature and B–H loop traces indicated a small hysteresis around the origin. Dc magnetoelectric studies were performed and outputs of 2.52 mV/cm/Oe and 2.49 mV/cm/Oe respectively were obtained for the unixially and isostatically pressed samples

Effect of HIPing on conductivity and impedance measurements of DyBi5Fe2Ti3O18 ceramics

X-ray diffraction, a.c. impedance and conductivity (a.c. and d.c.) have been used to characterize DyBi5Fe2Ti3O18. Samples were prepared by solid state double sintering method. A few samples were also subjected to hot isostatic pressing (HIP) at 800°C for 2 h at 100 MPa pressure. The data on XRD, impedance and conductivity of two sets of samples are compared to understand study of effect of HIPing on the properties of DyBi5Fe2Ti3O1