Development of dielectric materials is increasing with a rapid progress in mobile and satellite communications systems, where magnesium titanates find their place owing to good dielectric properties. Recently it has been established that, these materials, which are based on binary magnesium titanates (MgTi03 and Mg2Ti04) can be applied in MW engineering. These materials differ extremely low dielectric loss in the microwave range and high dielectric constant. On the other hand, barium-titanate compounds have attracted great attention for their specific microwave properties, as well. They were commonly used as parts of resonators, filters and multilayer ceramic capacitors, in the microwave region. The crystal phase with the structure BaZn2Ti40 11 is present in various commercial microwave dielectric materials based on barium-titanate compounds. Taking all this into account, in this article, the influence of mechanical activation of the MgO-Ti02 and BaCOr ZnO-Ti02 systems on phase composition, crystal structure and microstructure before and after sintering process, has been reported

Filipović, Suzana

Obradović, Nina

Pavlović, Vladimir B.

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Serbian Society for MicroscopyVinca Institute of Nuclear Sciences, University of BelgradeFaculty of Biology, Institute of Zoology, University of BelgradeInstitute for Biological Research "SiniSa Stankovic", University ofBelgradeFaculty of Technical Sciences, University of Novi SadPROGRAM AND PROCEEDINGS4th Serbian Congress for MicroscopyOctober 11-12. 2010Belgrade, Serbia4SCM-2010Edited by:Jasmina Grbovic NovakovicNatasa Nestorovic4th Serbian Congress for MicroscopySTRUCTURAL ANALYSES OF SINTERED MT ANDBZT CERAMICSNina Obradovic, Suzana Filipovic, Vladimir PavlovicInstitute of Technical Sciences-SASA, Belgrade, SerbiaI. I TRODUCTIONDevelopment of dielectric materials is increasing with a rapid progress inmobile and satellite communications systems, where magnesium titanates find theirplace owing to good dielectric properties. Recently it has been established that, thesematerials, which are based on binary magnesium titanates (MgTi03 and Mg2Ti04) canbe applied in MW engineering. These materials differ extremely low dielectric loss inthe microwave range and high dielectric constant [1-3].On the other hand, barium-titanate compounds have attracted great attention fortheir specific microwave properties, as well. They were commonly used as parts ofresonators, filters and multilayer ceramic capacitors, in the microwave region [4]. Thecrystal phase with the structure BaZn2Ti40 11 is present in various commercialmicrowave dielectric materials based on barium-titanate compounds [5].Taking all this into account, in this article, the influence of mechanicalactivation of the MgO-Ti02 and BaCOr ZnO-Ti02 systems on phase composition,crystal structure and microstructure before and after sintering process, has been reported.2. EXPERIMENTMixtures of MgO and Ti02 powders at a molar ratio MgO:TiOz = 2: I weremechanically activated in a high energy planetary ball mill (Retsch type PH 100).Mixtures of BaC03, ZnO and Ti02 powders at a molar ratio BaC03:ZnO:TiOz = 1:2:4were mechanically activated, also. The milling process of MT system was performed inair for 5 to 120 minutes and for BZT system for 20 to 80 minutes. Ball to powdermixture mass ratio was 20: I. Samples were denoted as MT-0 to MT-120 and BZT-0 toBZT-80, according to the milling time.The binder-free powders were compacted in an 8 mm diameter tool. Compactswere placed in an alulllila boat and heated in a tube furnace (Lenton Thermal Design Typ1600). MT compacts were sintered isothermally at 1100 to 1400°C and BZT compactswere sintered isothermally at 1100 to l300°C for 2h. The heating rate was lOoC/min. Themorphology of obtained powders before and after beating was characterized by scanningelectron microscopy (JEOL JSM-6390 LV). The pallets were cracked and covered withgold in order to perfoml these measurements. X-ray powder diffraction patterns aftermilling and thermal treatment were obtained using a Philips PW-1050 diffractometerwith ACu-Ka radiation and a step/time scan mode ofO.05°/ls.754th Serbian Congress for Microscopy3. RESULTS AND DISCUSSIONHigh-energy ball milling as method to synthesize nano size materials has manyadvantages, such as simplicity, relatively inexpensive to produce, applicable to any classof materials, etc [6]. It has been established that sintering temperature is lowered downowing to magnesium-titanate and barium-zinc-titanate preparation in nanocrystallineform.Fig. 1. SEM micrographs of(a) MT-O and (b) BZT-O sintered at JJOO°Cfor 2h.Formation of contact necks at the beginning stadium of sintering process isclearly visible at Fig. I. (a). Grains still own their starting shape, no relevant masstransport has been observed. Insufficiently sintered sample with in places formation ofcontact necks are the main characteristics for BZT-0 sintered sample, along with smallparticles of various compounds within the staliing sintering phase.4. CONCLUSIONFormation of various magnesium-titanate phases and pure barium-zinc-titanatephase along with densification process is observed during micrographs analysis. One cannotice that MT samples activated 120 minutes and BZT samples activated 80 minutesand sintered have advantageous microstructures, with the appropriate pores/materialsratio.5. REFERENCES[I] G. Pfaff, Ceram. Inter., 20 (1994) J11[2] H. Kang, L. Wang, D. Xue, K. Li, C. Liu, J. Alloys Compd., 460 (2008) 160[3] A. Belous, O. Ovchar, D. Durylin, M. Valant, M. Macek-Krzmanac, D. Suvorov, 1.Eur. Ceram. Soc., 27 (2007) 2963[4] W. Guoquing, W. Shunhua, S. Hao, Mat. Lett., 59 (2005) 2229[5] A. Balous, O. Ovchar, M. Macek-Krzmanc, M. Valant J. Eur. Ceram. Soc., 26,(2006)3733[6] K. T. Paul, S. K. Satpathy, I. Manna, K. K. Chakraborty, G. B. Nando, NanoscaleRes. Lett., 2 (2007) 39776

Structural analyses of sintered MT and BZT ceramics

Digital Repository of the Institute of Technical Sciences of SASA

Serbian Society for Microscopy
Vinca Institute of Nuclear Sciences, University of Belgrade
Faculty of Biology, Institute of Zoology, University of Belgrade
Institute for Biological Research "SiniSa Stankovic", University of
Belgrade
Faculty of Technical Sciences, University of Novi Sad
PROGRAM AND PROCEEDINGS
4th Serbian Congress for Microscopy
October 11-12. 2010
Belgrade, Serbia
4SCM-2010
Edited by:
Jasmina Grbovic Novakovic
Natasa Nestorovic
4th Serbian Congress for Microscopy
STRUCTURAL ANALYSES OF SINTERED MT AND
BZT CERAMICS
Nina Obradovic, Suzana Filipovic, Vladimir Pavlovic
Institute of Technical Sciences-SASA, Belgrade, Serbia
I. I TRODUCTION
Development of dielectric materials is increasing with a rapid progress in
mobile and satellite communications systems, where magnesium titanates find their
place owing to good dielectric properties. Recently it has been established that, these
materials, which are based on binary magnesium titanates (MgTi03 and Mg2Ti04) can
be applied in MW engineering. These materials differ extremely low dielectric loss in
the microwave range and high dielectric constant [1-3].
On the other hand, barium-titanate compounds have attracted great attention for
their specific microwave properties, as well. They were commonly used as parts of
resonators, filters and multilayer ceramic capacitors, in the microwave region [4]. The
crystal phase with the structure BaZn2Ti40 11 is present in various commercial
microwave dielectric materials based on barium-titanate compounds [5].
Taking all this into account, in this article, the influence of mechanical
activation of the MgO-Ti02 and BaCOr ZnO-Ti02 systems on phase composition,
crystal structure and microstructure before and after sintering process, has been reported.
2. EXPERIMENT
Mixtures of MgO and Ti02 powders at a molar ratio MgO:TiOz = 2: I were
mechanically activated in a high energy planetary ball mill (Retsch type PH 100).
Mixtures of BaC03, ZnO and Ti02 powders at a molar ratio BaC03:ZnO:TiOz = 1:2:4
were mechanically activated, also. The milling process of MT system was performed in
air for 5 to 120 minutes and for BZT system for 20 to 80 minutes. Ball to powder
mixture mass ratio was 20: I. Samples were denoted as MT-0 to MT-120 and BZT-0 to
BZT-80, according to the milling time.
The binder-free powders were compacted in an 8 mm diameter tool. Compacts
were placed in an alulllila boat and heated in a tube furnace (Lenton Thermal Design Typ
1600). MT compacts were sintered isothermally at 1100 to 1400°C and BZT compacts
were sintered isothermally at 1100 to l300°C for 2h. The heating rate was lOoC/min. The
morphology of obtained powders before and after beating was characterized by scanning
electron microscopy (JEOL JSM-6390 LV). The pallets were cracked and covered with
gold in order to perfoml these measurements. X-ray powder diffraction patterns after
milling and thermal treatment were obtained using a Philips PW-1050 diffractometer
with ACu-Ka radiation and a step/time scan mode ofO.05°/ls.
75
4th Serbian Congress for Microscopy
3. RESULTS AND DISCUSSION
High-energy ball milling as method to synthesize nano size materials has many
advantages, such as simplicity, relatively inexpensive to produce, applicable to any class
of materials, etc [6]. It has been established that sintering temperature is lowered down
owing to magnesium-titanate and barium-zinc-titanate preparation in nanocrystalline
form.
Fig. 1. SEM micrographs of(a) MT-O and (b) BZT-O sintered at JJOO°Cfor 2h.
Formation of contact necks at the beginning stadium of sintering process is
clearly visible at Fig. I. (a). Grains still own their starting shape, no relevant mass
transport has been observed. Insufficiently sintered sample with in places formation of
contact necks are the main characteristics for BZT-0 sintered sample, along with small
particles of various compounds within the staliing sintering phase.
4. CONCLUSION
Formation of various magnesium-titanate phases and pure barium-zinc-titanate
phase along with densification process is observed during micrographs analysis. One can
notice that MT samples activated 120 minutes and BZT samples activated 80 minutes
and sintered have advantageous microstructures, with the appropriate pores/materials
ratio.
5. REFERENCES
[I] G. Pfaff, Ceram. Inter., 20 (1994) J11
[2] H. Kang, L. Wang, D. Xue, K. Li, C. Liu, J. Alloys Compd., 460 (2008) 160
[3] A. Belous, O. Ovchar, D. Durylin, M. Valant, M. Macek-Krzmanac, D. Suvorov, 1.
Eur. Ceram. Soc., 27 (2007) 2963
[4] W. Guoquing, W. Shunhua, S. Hao, Mat. Lett., 59 (2005) 2229
[5] A. Balous, O. Ovchar, M. Macek-Krzmanc, M. Valant J. Eur. Ceram. Soc., 26,(2006)
3733
[6] K. T. Paul, S. K. Satpathy, I. Manna, K. K. Chakraborty, G. B. Nando, Nanoscale
Res. Lett., 2 (2007) 397
76


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