Influence of Hafnium Doping on Properties of PLZT
Yasmin Bürkl, Theresa Kainz, Klaus Reichmann
15:00 - 17:00 Thursday 23 October 2014 Rechbauerstrasse 12, HSII When the performance of a ceramic material is to be modified, in many cases dopants are used to achieve this goal. Those can differ in the following parameters regarding the ions they are replacing: ionic radius, valency or atomic mass. It is difficult to discern in which way each single parameter influences the doped material, because usually ionic radius and atomic mass cannot be changed independently. The doping of lead lanthanum zirconate titanate (PLZT) with hafnium replacing zirconium gives the unique situation of observing the influence of atomic mass difference on the system while the other parameters mentioned above are not changed. The objective of this research was to investigate the influence of hafnium doping on the structural and electrical properties of PLZT.
Samples with zero to thirty atom-percent hafnium were synthesised using the mixed oxide method und subsequent sintering. All samples were prepared following the chemical formula Pb0,91La0,06V“Pb0,03Ti0,15(Zr1-xHfx)0,85O3) where x stands for the varying Hafnium content.
Using SEM the microstructure of the samples was investigated. It was found that between ten and twenty atom-percent Hafnium content the solubility decreased to the point where secondary phases were formed. Samples with a dopant concentration of twenty percent or higher all contained secondary phases, so they were excluded from electrical characterization.
Polarization of the samples was measured against an electrical field. The measurements showed that Hafnium doping had no linear influence on the saturation polarization and therefore no trend could be observed. However, an increased hafnium concentration leads to slightly slimmer hysteresis curves.
The dielectric constant and the loss factor were measured as a function of temperature at different frequencies. Three maxima were seen, two of them were at the same temperatures for all samples. One at approximately 105 °C and one at 185 °C, with the first only visible in the measurements of the loss factor. Another maximum was noted between 147 °C and 170 °C.
The data gained suggest that a change of atomic mass within a crystal using dopants has only small influence on the electrical properties of the material. It seems that changes concerning the ionic radius or the valency have the major impact on the performance of this material.
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