barium zirconate

POWDER SYNTHESIS &

SINTERING STUDIESOF

YTTRIA DOPED BARIUM ZIRCONATE

CONTENTSDoped Barium ZirconateApplications, advantages & disadvantages of

BZYSinteringSample PreparationCharacterizationResults and DiscussionConclusion

BARIUM ZIRCONATEPervoskite structure

When Barium Zirconate (BZ) is doped with Y2O3, oxygen vacancies are formed.

Y2O3 + BaZrO3 2YZr’ + 3Oo

x + Vooo

APPLICATIONS OF BZY

It is used as electrolyte and electrode material in Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC).

ADVANTAGES OF BZY

High stability with sufficient proton conductivity in the temperature range of 600-800o C

Greatly reduces material & fabrication problems

Improves cell reliability during prolonged operations

Stable in CO2 and H2O containing atmosphere

DISADVANTAGES OF BZY

Yttria doped barium zirconate material is difficult to sinter

SINTERING

Sintering simply means “coalescence of powder at elevated temperatures.”

The driving force operating during sintering is the reduction in surface energy.

SINTERING

Various atomic mechanisms:1. Evaporation – Condensation (path 1)2. Surface diffusion (path 2)3. Volume diffusion (path 3)4. Grain boundary diffusion (path 4)

SINTERING STAGESAn interval of geometric change in which pore shape is

totally defined (such as rounding of necks during the initial stage sintering) or an interval of time during which the pore remains constant in shape while decreasing in size

SAMPLE PREPARATION

Solid-state method Raw materials: BaCO3 , ZrO2 , Y2O3

Weighing and mixing/grindingCalcinationPelletization (uniaxial and cold isostatic

pressing)Solid state sintering

CHARACTERIZATION

Phase formationDensitySinteringMicrostructural studies

RESULTS & DISCUSSIONS1. XRD

20 30 40 50 600

50

100

150

200

1300 1350 1400

Inte

nsi

ty (

A.U

)

2

RESULTS & DISCUSSIONS2. PARTICLE MORPHOLOGY & PARTICLE SIZE DISTRIBUTION

Shape not exactly sphericalParicle size varied from 0.205 µm to 1.405 µmAverage particle size 0.649 µm

RESULTS & DISCUSSIONS3. SINTERING

Dilatometry

maximum shrinkage was 5.36 % at 1556o C

0 700 1400-6

-4

-2

0

Shr

imka

ge (i

n %

)

Temperature (in OC)

Temperature Vs Shrinkage

RESULTS & DISCUSSIONS3.SINTERING

Densification

Low densityGrain size was 200 – 500 nmSingle phase formation had taken place

RESULTS & DISCUSSIONS4. DENSIFICATION USING ZnO

By using ZnO, 92 – 94 % density was obtained.

CONCLUSION

Single phase formation BZY couldn’t be sintered properly even at

1550o CZnO helps in sintering

THANK YOU!!!