L. Del Olmo

Influence of calcium on the ferroelectricity of modified lead titanate ceramics

Abstract Lead titanate ceramics modified with 24, 30, 35 and 40 mole% of calcium have been obtained. The thermal behaviour of permittivity as well as that of pyroelectric coefficient present a larger broadening the larger the Ca content, which could be adscribed to an increasing disorder on the Ca and Pb arrangement. On the other hand the diminishing of tetragonality with increasing Ca amount causes the decrease of coercive field, which favors the 90° domain reorientation; the moderate strains produced on poling could justify the minimum poling reversal effects on piezoelectricity.

Sol-gel processing by inroganic route to obtain a TiO2PbO xerogel as ceramic precursor

Abstract The sol-gel process for ceramic preparation has been the focus of interest in the past few years. With this kind of chemical process it is possible to enhance the purity and reactivity of the system and to ensure the control of the microstructure of the obtained ceramics. Pure lead titanate has interesting properties as ferroelectric ceramic, but it has not been used because of its poor sinterability. In this work, a sol-gel process by the inorganic route of the TiO 2 PbO system is presented. With this process a xerogel is obtained which leads to pure PbTiO 3 ceramic materials after firing.

Contributions to the knowledge of calcium-modified lead titanate ceramics

Abstract It will be summarized here the work of the Ferroelectric Materials Group of this Institute on ceramics of calcium modified lead titanate during the past few years.

Ferropiezoelectricity of calcium modified lead titanate ceramics

When a ceramic with grain Boundaries rich in OPb is poled Beyond 4O kV cm−1 at ferroelectric phase, the highest anisotropy of electromechanical coupling factor is obtained. An attempt to explain this Behaviour is made in terms of domain switching and the strains and cracks generated during cooling down poling. Apart from composition, two more factors are revealed as contributing to the disappearance of radial coupling in Ca-modified lead titanate ceramics: microtexture and electric poling strategy.

PbTiO3 ceramic fibres prepared from a sol-gel process as piezoelectric materials

Abstract Fibres are formed by extrusion of a fresh gel with appropriate rheological characteristics. The gel was prepared using an inorganic sol-gel process. Ageing of extruded fibres leads to TiO2PbO xerogel fibres. Dehydratation, synthesis and sintering were carried out in a unique firing process. PbTiO3 ceramic fibres with a singular microstructure were obtained.

Electric poling effect on piezoelectricity of calcium modified lead titanate ceramic

Abstract The highest anisotropy of electromechanical coupling factor in a calcium modified lead titanate ceramic is obtained when for a given composition and ceramic micro-texture of free pbO into the grain boundaries, the electric poling is performed at the ferroelectric phase and as close as possible to the Curie temperature. Electric poling starting at the paraelectric phase leads to Kp ≠ O even for further poling at the ferroelectric phase.

Piezoelectric behavior of Pb1−X CaX TiO3 ceramics obtained by reactive processes

Abstract Canmodified PbTiO3 ceramics were obtained from oxides and carbonates. By adding controlled quantities of NO3H during one of the process stages the reactivity in the synthesis and sintering is increased. Relations between microstructure and piezoelectric properties are established.

Piezoelectric behaviour of pure PbTiO3 ceramics

Piezoelectric behaviour of pure PbTiO3 ceramics is studied after their poling in the ferroelectric phase with electric fields from 10 KV.cm-1 to 110 KV.cm-1. Experimental data reported indicate the dependence on ceramic microstructure, which corrleates with piezoelectric properties of these ceramics. These properties show a high potential use of PbTiO3 ceramics in electromechanical devices at high frequency and high temperature.

Extruded ceramic fibres of modified lead titanate including sol-gel precursors

An original procedure to obtain extruded ceramic fibres of calcium modified lead titanate has been developed. Slurry preparation was made by homogeneous mixture of crystalline ceramic powder with a gel of analogous composition acting as plasticizer. In addition, the gel phase provides a binder elect to the green fibres after extrusion and during the first stage of the firing process. On the other hand, the high reactivity of the gel accelerates the sintering mechanisms. Fibres of ∼ 1 mm final diameter and 97% of the theoretical density were obtained for moderate sintering conditions (1000° C, 3 to 7 h). The microstructure of the fibres was studied in comparison with those of ceramics prepared from each of the two components separately. Since electromechanical properties of these types of ceramics strongly depend on the microstructure, the procedure here developed is considered very appropriate for their processing.

Crystallization from a gel of calcium modified lead titanate

Abstract XRD, DTA, Raman spectroscopy and piezoelectric measurements were made for a gel of calcium modified lead titanate, calcinated at increasing temperatures. At the first stages, crystallinity progresses as a deformed pseudocubic lattice close to CaTiO3. When temperature increases, PbTiO3 distorted lattice becomes predominant; then beyond 800° the structure is finally completely ordered. Results suggest ferroelectric nature from the very begining of treatments.