Ceramic Activity

As part of the ceramic activity the research in the following areas is being pursued:

- Transparent Ceramics

- Relaxor Ferroelectrics

- Multiferroics

- Major facilities

Click below for further information:

Transparent Ceramics

Monolithic growth of free-standing ZnS was carried out using sub-atmospheric pressure chemical vapour deposition (CVD) (Figure 1). Transparent Nd and Yb-doped PLZT have been fabricated using hot-press sintering (Figure 2). Currently development of Nd-YAG and Yb-Y2O3 ceramics are being pursued.

Free-standing transparent ZnS blanks and dome
 
Nd-PLZT ceramics and UV-Vis-NIR transmission
 
Yb-PLZT ceramics and UV-Vis-NIR transmissione
 

Relaxor Ferroelectrics

The mechanism of relaxation and relaxor to normal-ferroelectric transformation in (1-x)PMN-xPZ solid solutions has been investigated. A cross-over in the composition range 0.42 < x < 0.46 was observed. The piezoelectric (d33) and electromechanical (k31) coefficients were maximum in the vicinity of the cross-over region.

Shape-memory strain in thin bars of PMN-PT ceramic for compositions near its morphotropic phase-boundary has been observed. The maximum pseudo-plastic strain measured was ~ 0.3% in 65/35 PMN-PT and was found to be inversely related to the relaxor characteristic parameter “γ” (Figure 2). These studies showed that the pseudo-plastic strain depends on the composition, La3+ ions doping concentration, temperature, pressure, and thermal history.

Multiferroics

Effect of La, Nd, Er, Ca and Eu doping on cycloid ordering of Fe3+ ions in BiFeO3 and on the coupling between the magnetic and ferroelectric properties has been studied. In Bi0.9-xLa0.1NdxFeO3 (BLNFOx) and Bi0.9-xLa0.1ErxFeO3 (BLEFOx) ceramics, weak magnetism and ferroelectric polarization was observed. Ca-doping was found to enhance the oxygen vacancies which lead to weak ferromagnetism. Anomaly at TN was found in temperature dependent dielectric studies for Eu-doped sample.


Ferroelectric Thin Films and Nano-composites:

[I] X-ray diffraction patterns of LT thin films [II] AFM images of mono layer LT thin film on Sapphire (006) substrate

LT thin films have been deposited on Silicon (111), [Pt (111)/TiO2 /SiO2/ Si (100)](Pt-Si), and sapphire (006) substrates by spin-coating method. The LT thin films are randomly oriented on Pt-Si and Silicon substrates. C-orientated LT thin films could be deposited only on sapphire substrates.


Deposition and characterization of multilayer LiTaO3 (LT) thin films:

Multilayer LT thin films were deposited on Pt-Si [Si(111)/SiO2/TiO2/Pt(111)] substrate to get rid of conductivity problem in single layer thin films.


Nanoparticles:

Lithium tantalate (LiTaO3) and Lithium niobate (LiNbO3) nanoparticles were synthesized by sol-gel process using capping ligands. Pure yttrium oxide (Y2O3) and Yb doped Y2O3 (Yb: Y2O3) nanocrystalline powders were synthesized by the carbonate solution route. Calcination time, temperature and pH were optimized to obtain phase pure nanoparticles.


Nano composites:

PVDF films (30µm thick), embedded with 20-40nm sized nanocrystallites of LT were fabricated to utilize them for pyroelectric sensor applications. The ferroelectric polarization and the pyroelectric coefficient of LT/PVDF nano composite films increase with increase in volume fraction of LT in LT/PVDF. Since LT/PVDF composite requires lower poling fields and has higher polarization as compared to PVDF, therefore it should prove as an attractive material for pyroelectric sensor applications.

Major facilities

  • Impedance analyzer (HP4194A Hewlett Packard, USA and Nova control, France) for dielectric and impedance studies in the temperature range (150-800K) and frequency range 1mHz to 40MHz .
  • Powder X-ray diffractometer (18kW and 3kW, Rigaku, Japan)
  • Hystersis loop tracer (Radiant, USA) for Polarization vs. Electric Field and Strain vs Electric Field measurements.
  • Hot-press (Therlek, India) for sintering (Tmax=1250oC) of ceramic samples under load (Max. 5Tons).
  • Polarizing Light Microscope (BX60,Olympus, Japan) equipped with hot-stage (Linkam).
  • Thickness measurement unit (Filmatrics, USA.)
  • Physical vapour deposition unit (Hind High Vacuum, India).
  • Viscometer.
  • Several box- and muffle furnaces for the synthesis and sintering of materials
  • Spin-coating unit for making thin-film ferroelectric ceramics in a controlled atmosphere.
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