Piezo and pyroelectric properties of PZT thick films

Transcription

1 Piezo and pyroelectric properties of PZT thick films 1st International Workshop on Smart Materials and Structures, 7 th & 8 th October 2004 Dr Robert Dorey

2 Introduction Why thick films? Processing issues Processing techniques Properties Applications

3 Introduction Why thick films? Processing issues Processing techniques Properties Applications Why thick film?

4 Introduction Signal-to-noise ratio Sensitivity Co-processing SN S CP 1. Bulk processing SN 2. Tape Cast SN / S 3. Sol Gel S / CP Alternatives?

5 Why thick films? Processing issues Processing techniques Properties Applications Processing issues

6 Processing Issues Temperature Reactions Volatile compounds Shrinkage

7 Processing Issues Temperature Reactions Degradation of: Substrates Electrodes Volatile compounds Shrinkage

8 Processing Issues Temperature Reactions Volatile compounds Reaction with: Substrates Electrodes Pb + Si = 714ºC Shrinkage

9 Processing Issues Temperature Reactions Volatile compounds Evaporation of Pb Shrinkage

10 Processing Issues Temperature Reactions Volatile compounds Shrinkage Shrinkage relative to substrate

11 Why thick films? Processing issues Processing techniques Properties Applications Processing techniques

12 Processing techniques Screen printing Electrophoresis Composite sol gel

13 Processing techniques Screen printing Electrophoresis Composite sol gel

14 Processing techniques PZT sol Composite sol gel Spinning of composite slurry PZT powder Mix Dry Pyrolyse Sinter & Crystallise Sol Infiltration & spinning

15 Processing techniques PZT Ti/Pt Si (C+0S)4 Composite sol gel film

16 Processing techniques Pt (111) 100 normalised counts composite sol gel film PZT powder theta (100) (110) (111) (200) (210) (211)

17 Sintering aid & Infiltration Sintering aid Processing techniques (C+0S)4 (C+0S)4 (C+4S)4 (C+4S)4 Infiltration

18 Processing techniques Stepped composite sol gel film Graded composite sol gel film

19 Processing techniques Screen printed composite sol gel

20 Why thick films? Processing issues Processing techniques Properties Applications Patterning

21 Patterning Wet Etching Substrate

22 Patterning Powder Blasting

23 Why thick films? Processing issues Processing techniques Properties Applications Properties

24 Properties Difficult to compare films Factors which can affect properties: Composition Film thickness Grain size Stress state Crystal orientation

25 Properties Relative permittivity relative permittivity Hard PZT Soft PZT Sol Infiltration steps Very similar results for hard and soft doped systems

26 Properties Piezoelectric Coefficient d 33, f Hard PZT Soft PZT 70 d 33, f (pc/n) Sol Infiltration steps

27 Properties Piezoelectric Coefficient e 31, f 6 5 Hard PZT Soft PZT e 31, f (C/cm 2 ) Sol Infiltration steps

28 Properties Hysteresis Polarisation (µc/cm 2 ) Polarisation (µc/cm 2 ) Field (V/µm) Field (V /µm) Bulk PZT (PZ26) -40 ComFi (PZ26)

29 Properties Poling (X-ray Diffraction) - prediction I I I (002) (200) 2θ (002) (200) 2θ (002) (200) 2θ Before Poling During Poling After Poling

30 Properties Poling (X-ray Diffraction) Grain size broadening

31 Properties Poling (X-ray Diffraction) Stress broadening

32 Properties Pyroelectric Relative Permittivity Relative Permittivity Loss Sol infiltration/pyrolysis stages Loss (%)

33 Properties Pyroelectric 3.00E-04 Pyroelectric coefficient (Cm -2 K -1 ) 2.50E E E E E E Sol infiltration treatments

34 Properties Pyroelectric Figure of merit Fv (x10-2 m -2 C -1 ) Fd (x10-5 Pa -1/2 ) Fv Fd Screen printed material sintered at 1100 ºC Sol infiltration treatments F D = c' ( ε ε tanδ ) 1 2 o r p F V = p c ' ε ε o r

35 Properties Pyroelectric T max ε Loss (%) p (x10-4 Cm -2 K -1 ) F V (x 10-2 m 2 C -1 ) F D (x 10-5 Pa -1/2 ) PMNZT U ºC Tape cast PMNZT U 1250ºC Screen PZTZN & PLZT 1100ºC ComFi 700ºC

36 Why thick films? Processing issues Processing techniques Properties Applications Examples of applications

37 Applications 200 MHz Ultrasonic transducer

38 Applications Unimorph structures Multi-arm actuator prototype PZT Si diaphragm prototype structure (image courtesy of EPFL- Parmenide project)

39 Acknowledgements Thanks to: Silvia Marson Fabrice Duval Steve Wilson Qi Zhang Andrew Steckl Jason Heikenfeld Chanaka Munasinghe Royal Academy of Engineering Engineering Physical Sciences Research Council

40 Thank you.