EUROPEAN CONCERTED ACTION

ON

FERROELECTRIC CERAMIC THIN FILMS

COST 514

RESEARCH PROPOSAL ON:

"FERROELECTRIC CERAMIC THIN FILMS FOR PYRO AND PIEZOLECTRIC APPLICATIONS"

Name of the applicant institution:

Université du Maine. France.

Laboratory which is to carry out the studies:

Laboratoire du Physique et l'Etat Condensé (LPEC)

Université du Maine. BP535

72085 Le Mans cedex. France

Phone: 33 (0) 243833268

FAX: 33 (0) 243833518

e-mail: daniel.chateigner@univ-lemans.fr

Scientist responsible for the project: Dr. Daniel CHATEIGNER (same address)

Name of alternate colleagues: Dr. Jesús. RICOTE

Prof. Alain GIBAUD

Proposed effort in man/years per annum of graduates, scientist and technicians:

1 postdoc, 2 scientist, 1 technician.

Project Duration: 10 months

Starting date: 1st September 1998

Other laboratories involved in the project:

1/ Prof. J. Mendiola, Instituto de Ciencia de Materiales de Madrid, CSIC, Madrid, Spain.

2/ Dr. D.A. Hall, Materials Science Centre, University of Manchester, Manchester, UK.

3/ Ms. W. W. Wolny, Ferroperm, Ltd. Piezoceramics Division, Kvistgard, Denmark.

4/ Dr. E. Snoeck, CEMES-LOE, CNRS, Toulouse, France.

DESCRIPTION OF THE PROPOSAL

 

  1. Aim of the study.

Ca1 and La2 modified lead titanate (MPT) ferroelectric thin films have recently being recognised as excellent candidates for piezoelectric applications due to their high d33 values. MPT compositions are also well-know as appropriated for pyroelectric materials. The aim of the proposed study is to carry out a quantitative texture analysis of MPT ferroelectic thin films, and correlate these results with the macroscopic properties, which make these materials interesting for pyro and piezoelectric applications, for example, Surface Acoustic Wave (SAW) devices and microactuators.

 

2.2 Reasons justifying the study

One of the factors determining the behaviour of ferroelectric thin films is the presence of any preferred crystallographic orientation, or texture. Until recently, most of the studies only examined the intensities of one or two major X-ray reflections, which in certain cases can be characteristic of a given texture. Although some interesting works can be found in the literature3, complete quantitative texture studies, measuring diffraction pole figures with a goniometer and calculating orientation distributions (OD), have not been carried out extensively on ferroelectric thin films4. The analysis of the pole figures can produce a real and accurate picture of the texture of the thin films, in aspects such as the strain distribution in the film and the the relative orientation of the 90 domains with respect to the substrate. Correlations with the polarization state and with final switching performances should be possible and are essential for an analysis of the texture influence in pyro- and piezoelectric applications.

1 A. Kholkin, M.L. Calzada, P. Ramos, J. Mendiola and N. Setter. Appl. Phys. Lett. 69 (3), 3602-3604 (1996).

2 M. L. Calzada, M. Algueró and L. Pardo. 2-EMIF. Jouy-en-Josas (France). September, 1997.

3 M. de Keijser, D.M. de Leenw, P.J. van Veldhoven, A.E.M. Veirman, D.G. Neerinck and G.J.M. Dormans. Thin Solid Films 266, 157-167 (1995).

4 D. Chateigner, H.R. Wenk, A. Patel, M. Todd and D.J. Barber, Integrated ferroelectrics 19[1-4] (1998, in press)

 

 

2.3 Practical value of the project.

The various methods used for the preparation of ferroelectric thin films will be tested in relation to the production of different types of textured materials. This will result in a better knowledge of the factors which lead to the appearance of textured structures.

Comparison to physical properties and the determination of their correlation with the texture, will allow to determine the most appropriate preparation parameters to produce materials for specific applications.

 

2.4. Plan of research.

X-ray diffraction pole figures of ferroelectric thin films will be measured using a texture goniometer. An analysis of the pole figures and OD refinement will follow, in order to identify and quantify texture components.

The thin films will be modified lead titanates produced by either sol-gel or laser ablation. Results will be correlated to the different processing parameters and methods. Polarisation values will be also compared to the textures obtained.

 

2.5. Competence of the laboratory.

The LPEC (Le Mans) is equipped with a 4 circle Huber X-ray diffractometer with a INEL position sensitive detector used for the quantitative texture analyses, and a D5000 (Philips) high resolution reflectometer. New high speed computers (300 MHz, 128 Mb RAM PC) are dedicated to these experiments which necessitate long CPU time (several hours for a regular Texture-Structure combined experiment).

The calculations for the texture analysis (pole figures, OD, inverse pole figures, component simulations ...) are conducted using the up to date Berkeley Texture Package [Wenk et al., 1998], and own local programs are used for the reflectivity simulations.

At LPEC, a specialist in texture analysis (Dr. Chateigner) an one in reflectivity (Prof. Gibaud) are in charge of the X-ray experiments. The expertise in ferroelectric thin films is reinforced by a visitor scientist ( Dr. Ricote ). Some recent publications of the applicants related to the topic of this research proposal, showing their experience in this area, are listed below:

- D. Chateigner, H.R. Wenk, A. Patel, M. Todd and D.J. Barber "Analysis of preferred orientation in PST and PZT thin films on various substrates" Integrated ferroelectrics 19[1-4] (1998, in press)

- V. Bornand, D. Chateigner, Ph. Papet and E. Philippot "Heteroepitaxial growth of LiTaO3

thin films by pyrosol process" Integrated ferroelectrics (1998, in press).

- H.R. Wenk, S. Matthies, J. Donovan and D. Chateigner "BEARTEX: A windows based program for quantitative texture analysis" J. Appl. Cryst. (1998, in press).

- A. Gibaud, N. Cowlam, G?. Vignaud and T. Richardson "Evidence of self-affine rough interfaces in a Langmuir-Blodgett film from X-ray reflectometry" Phys. Rev. Lett. 74, 3205 (1995).

- J. Ricote, E Snoeck, R. Coratger and L. Pardo "Microstructural studies of sol-gel processed

Sm modified lead titanate thin films" J. Phys. Chem. Sol. 59 (2), 151-157 (1998).

- M.L. Calzada, R. Sirera, J. Ricote and L. Pardo "Solution processing and crystallisation of ferroelectric samarium modified lead titanate thin films" J. Mater. Chem. 8(1), 111-118 (1998).

 

2.6. Cooperation

The LPEC of the university of Le Mans will cooperate with the COST action members:

- Prof. J. Mendiola, Instituto de Ciencia de Materiales de Madrid, CSIC, Madrid, Spain.

This partner will supply the MPT thin films processed by sol-gel and required for this study, together with the processing details necessary to obtain correlation processing-texture. Polarisation data, obtained from ferroelectric hysteresis loops and switching curves, and pyroelectric coefficients will be also provided by this group and used to analyse the role of texture in the macroscopic properties.

- Ms. W. W. Wolny, Ferroperm, Ltd. Piezoceramics Division, Kvistgard, Denmark.

This partner supplies the ceramic targets for processing of thin films by laser ablation deposition and performs characterisation of thin film surface roughness.

 

 

- Dr. D.A. Hall, Materials Science Centre, University of Manchester, Manchester, UK.

This partner tests thin films for their use in SAW devices.

- Dr. E. Snoeck, CEMES-LOE, CNRS, Toulouse, France.

This partner carries out the microstructural analysis of the thin films by TEM and electron diffraction.

 

Final remarks:

It is foreseen the incorporation to the COS514 Action of a project by Prof. Whatmore (Cranfield University, UK), which will result in the processing of PZT films that could also be studied within this project.

Through the cooperation with groups that are in the COST514 Action , it is foreseen that it were possible to measure the d33 coefficient of the studied films by mean of laser interferometric techniques.