THE INFLUENCE OF STRUCTURE AND COMPOSITION ON THE THERMODYNAMIC, ELECTRICAL AND MAGNETICAL CHARACTERISTICS OF MICRO AND NANOSTRUCTURED OXIDE MATERIALS WITH SPECIAL MAGNETOREZISTIVE PROPERTIES

(CMR-TEM)


  Abstract

  Objectives and activities

  Partners

  Results

  Links

 


OBJECTIVES AND ACTIVITIES

Year I - 2006     

 

Objective

Activities

1

To identify new collossal magnetoresistive (CMR) micro and nanostructured transition metals oxides from the systems: La(Sr, Ca, Ba)-Mn(Co, Fe, Al, In) -O. Methodology elaboration.

1.1 Identification of new micro and nanostructured magnetoresistive (CMR) oxides on the basis of the complexity of their thermodynamics characteristics. The set-up of the experimental methodology regarding the thermodynamic study


1.2 Identification of new micro and nanostructured magnetoresistive (CMR) oxides on the basis of the structural and RES spin dynamics characteristics. Elaboration of the specific methods for the structural and morphological characterization.


1.3 Selection of new magnetoresistivee compounds on the basis of the electrical and magnetic characteristics: critical temperature Tc, magnetization M, Curie-Weiss temperature.


1.4 Selection of new oxide materials CMR taking into account the influence of the doping amount and grain size reduction on the RES spectral parameters.


1.5 Elaboration of the experimental methology required by the pirosynthesis method of preparation of the new compounds.

 

Yearl II - 2007     

 

Objective

Activities

1

Synthesis of some micro and nanostructured materials from the system La1-xAxMn1-yByO3 (where A = Ca, Sr; 0<x<1; B=Fe, Co; 0<y<0.1) by advanced experimental methods and techniques.

1.1 Synthesis of the microstructured materials from the La1-xAxMn1-yByO3 system by solid state reaction method.

1.2 Synthesis of the nanostructured materials from the La1-x AxMn1-yByO3 system by sol-gel method.

1.3 Synthesis of the microstructured materials La1-xAxMn1-yByO3 by specific methods of the powder metallurgy.

1.4 The set-up of a new, nonconventional method for in situ obtaining of new compounds with predetermined composition by the oxygen stoichiometry variation under controlled conditions.

 

2

The set-up of new cells and apparatus for the experimental measurements.

2.1 The set-up of the experimental apparatus for EMF measurements and solid state coulometric titration (two new work cells).

2.2 Proposal of a new method for the evaluation of the oxygen vacancies contribution in balancing and ordering the local charge in CMR compounds.

2.3. The set-up of the experimental apparatus for electrical resistivity measurements.

2.4. The set-up of the experimental apparatus for Seebeck effect investigation.

2.5. The set-up of the experimental apparatus for the study of the Hall effect.

2.6. The set-up of the experimental apparatus for RES measurements.

2.7 Preliminary experimental measurements for the verification of the installations used for the characterization of the new materials by specific methods.

 

3

Experimental measurements for the characterization of the new materials.

3.1.Experimental measurements for the thermodynamic characterization of the substituted compoundsi La1-xAxMn1-yByO3-d .

3.2. Measurements for the spin dynamic characterization of the nano and macrocrystalline compounds.

3.3. Measurements of the magnetic characterization of the substituted compounds.

 

4

The study of the correlations between the properties and different compositional variables.

4.1. Correlations of the thermodynamic properties with the changes in compositions. The influence of the nature and substituents concentration on the thermodynamic properties.

4.2. Thermodynamic investigation of the nonstoichiometric compounds obtained in situ.

4.3. The evaluation of the structure defects contribution (oxygen vacancies, Mn4+ ions concentration).

4.4. The effect of the oxygen stoichiometry variation on the spin dynamics and magnetic double exchange mechanism.

4.5. The influence of particle size on spin dynamics and magnetic double exchange mechanism.

4.6. Modification of the magnetic properties as a function of nature and concentration of the substituents.

 

5

The results dissemination.

5.1 Scientific papers published or submitted for publication.

5.2 Scientific papers communicated at international scientific manifestations.

5.3 Scientific papers communicated at national scientific manifestations.

5.4 Exposures at the brokerage actions related to EU FP7 Program.

5.5 Prezentari in cadrul sedintelor Platformei Europene de Nanomedicina si a Associated Phase Diagram and Thermodynamics Committee.

5.6 PhD Thesis in the field.

5.7 Training for young researchers.

5.8 Organizing of a scientific manifestation in the view of the project results dissemination.

 

Year III - 2008

 

Objectives

Activities

1

Synthesis of compounds in the systems La-Ca(Sr)-Mn-O, La-Ca-Mn-Al(Fe)-O

1.1 Synthesis of two sets of compounds by both solid state conventional method and sol-gel method
1.2 Structural characterization of the obtained compounds

2

Obtaining of new phases in the La-Ca(Sr)-Mn-O, La-Ca-Mn-Al(Fe)-O systems

2.1 Obtaining in situ of new micro- and nanostructured compositions by the oxygen stoichiometry variation (solid state coulometric titration)
2.2  Structural and morphological characterization of the obtained compounds

3

Thermodynamic data of compounds in La-Ca(Sr)-Mn-O, La-Ca-Mn-Al(Fe)-O systems

3.1 Experimental measurements on cells under the open circuit condition
3.2 Experimental measurements by DSC  (HTDSC)

4

Investigation of compounds in the La-Ca(Sr)-Mn-O, La-Ca-Mn-Al(Fe)-O systems based on a complex analysis of the energetic parameters

4.1Correlation between thermodynamic properties and the nature and concentration of the substituents
4.2 Correlation between thermodynamic properties and the particle size in micro and nanostructured compounds

5

Investigation of new nonstoichiometric compositions obtained in situ

5.1 Experimental EMF measurements coupled with solid state coulometric titration measurements
5.2 Correlation between thermodynamic properties and the oxygen nonstoichiometry

6

Criteria for materials selection in the view of specific applications

6.1 Correlation of the thermodynamic data with the structural defects
6.2 Criteria for the materials selection in the view of specific applications

 

Year IV - 2009

 

Objectives

Activities

1

The study of the polymorph phases in the oxide systems: ZrO2, Al2O3, TiO2

1.1 DSC (HTDSC) experimental measurements – in bulk
1.2 Calculation of the thermodynamic data

2

The synthesis of the nanocrystalline powders

2.1 The synthesis of the nanocrystalline powders
2.2  Structural and morphological characterization of the obtained powders

3

The study of the influence of grain/crystallite size on the thermodynamic data

3.1 Experimental measurements by DSC  (HTDSC) for nanocrystalline samples

4

The comparative study of the energetic parameters
(the transformation enthalpies, entropies, energies) on powders and tablets

4.1 Correlation between thermodynamic properties on powders and tablets

5

Obtaining of the phase diagrams in the oxide systems

5.1 The data analysis for the phase diagrams evaluation
5.2 The complex approach of the inter-relation between the method of synthesis, microstructure, properties.

6

Conclusions on the thermodynamics of the polymorph phases in nanostructuired systems

6.1 Correlation of the thermodynamic data of the polymorph phases in selected systems
6.2 Conclusions on the energetics of the polymorph phases.