Posibilitati de control al structurii si morfologiei nanoparticulelor de BaTiO 3

Transcription

1 Posibilitati de control al structurii si morfologiei nanoparticulelor de BaTiO 3 Strategies for the structure and morphology control of BaTiO 3 nanoparticles

2 Florentina Maxim Laboratorul de Termodinamica Chimica, Institutul de Chimie Fizica Ilie Murgulescu al Academiei Romane, Bucuresti UNIVERSITY OF AVEIRO, PORTUGAL

3 Outline State of the art Experimental & Results Main Contributions Lessons learned

4 State of the art - BaTiO 3 Structure Ba - A site cation Oxygen Ti - B site cation Non Centrosymmetric Centro-symmetric Dielectric Constant Phase Transitions 120 o C 5 o C Cubic -90 o C Tetragonal Orthorhombic Rhombohedral Spontaneous polarization P E Temperature Switching Ferroelectric

5 Ferroelectrics Applications ML Capacitors Piezo Generators Piezo Motors Piezo Actuators Electrostrictive Actuators PTC Sensors BULK Dielectric Capacitors IR Sensors Piezo Sensors And Actuators Electrooptic Shutters Electrooptic displays FILMS Non Volatile Memories Integrated optics AR Coatings Haertling, J. Am. Ceram. Soc., 82, (1999)

6 New demands Smaller, faster, cheaper, quicker is the mantra, as users seek to increase the level of functionality they have in all their devices. Dr. Paul A. Magill (2009) Miniaturization electronic devices Micro-scale thermoelectric cooler The Smarter IC Memory TI 130nm FeRAM The World s Smallest Piezoelctric Motor Nanotechnology

7 BaTiO 3 at nanoscale? Phase Transitions Diffuse at nanoscale Dielectric Constant 120 o C 5 o C Cubic -90 o C Tetragonal Orthorhombic Rhombohedral Dielectric Constant Rhombohedral Orthorhombic Tetragonal Cubic Temperature Spontaneous polarization P Decreasing at nanoscale P Temperature E E

8 Anisotropic Ferroelectrics? Enhancement of ferroelectric properties in anisotropic 1D nanoferroelectrics Morozovskaa et al, Physica B: Condensed Matter. (2007) Nanorods Spontaneous polarization Increasing for 1D P Nanobelts E Nanowires For this is needed to study the anisotropic growth

9 Synthesis Strategies Hydrothermal synthesis Template Non-template Chemical template using TiNTs Additive assisted using Ti alkoxides

10 Template Strategy

11 Chemical Template - Experimental Ba(OH) 2 (aq) Layered A 2 Ti 2 O 5 -TiNTs Ba aq Ba aq Ba aq TiNTs Ba aq Hydrothermal Synthesis 90 ºC, 110 ºC, 200 ºC Various times BaTiO 3 X-Ray SEM & TEM Raman PFM

12 Structure Temperature, Time 200 C Gradual from pseudo-cubic to tetragonal 110 C 90 C 24 h XRD 6 h Raman 30 Maxim et al., Crystal Growth & Design, Maxim et al., Crystal Growth & Design, Maxim et al., Processing and Application of Ceramics, 2010.

13 Morphology Temperature, Time early stage intermediate stage wild Round shaped long stage SEM Maxim et al., Crystal Growth & Design, Maxim et al., Crystal Growth & Design, Maxim et al., Processing and Application of Ceramics, Seaweed

14 We proved Maxim et al., Crystal Growth & Design, Maxim et al., Processing and Application of Ceramics, Maxim et al., Crystal Growth & Design, Cubic BT At high temperature, high time wild Seaweed At low temperature, low time Tetragonal BT

15 Non Template Strategy

16 NonTemplate - Experimental Ti[OCH(CH 3 ) 2 ] 4 [NaOH] Ti[O(CH 2 ) 3 CH 3 ] 4 PAA PVP SDS HPMC Ti[OCH(CH 3 ) 2 ] 4 Ti[O(CH 2 ) 3 CH 3 ] 4 NaOH (aq) Ba(CH 3 COO) 2 O - O - Ti 4 O O Ba 2+ [O-Ti-O] n Ba 2+ Hydrothermal Synthesis 90 ºC, 110 ºC, 200 ºC Various times BaTiO 3 X-Ray SEM & TEM Raman PFM

17 Morphology Ti precursor Ti[OCH(CH3)2]4 A 12-a 12-a ediţie ediţie aa Seminarului Seminarului Naţional Naţional de de Nanoştiinţă Nanoştiinţă şi şi Nanotehnologie, Nanotehnologie, A Biblioteca Academiei Academiei Române, Române, Bucureşti Bucureşti Biblioteca Ti[O(CH2)3CH3]4

18 Morphology NaOH concentration Ti[OCH(CH3)2]4 A 12-a 12-a ediţie ediţie aa Seminarului Seminarului Naţional Naţional de de Nanoştiinţă Nanoştiinţă şi şi Nanotehnologie, Nanotehnologie, A Biblioteca Academiei Academiei Române, Române, Bucureşti Bucureşti Biblioteca

19 Morphology Additives Ti[O(CH 2 ) 3 CH 3 ] 4 blank PVP SDS PAA HPMC

20 Conclusions Template Chemical template using TiNTs TiNTs induce the anisotropic growth of BT Non-template Additive assisted using Ti alkoxides Different Ti precursors different morphologies of BT particles The structure and the morphology of BT nanoparticles can be controled by hydrothermal synthesis

21 ACKNOWLDGEMENTS PhD supervisors: Prof. Dr. Paula Vilarinho Dr. Paula Ferreira Post-doc supervisors: Prof. Dr. Joaquim Vieira Prof. Dr. Augusto Lopes Scientific mentor: Dr. Speranta Tanasescu PN-II-RU-TE Team members: Dr. Daniela Berger Iuliana Poenaru Andreea Iorgu

22 VA MULTUMESC PENTRU ATENTIE!