PhD Thesis Arne Lüker final version V4 - Cranfield University

Polarisation [µC/cm²]
25
20
15
10
5
0
-5
-10
-15
-20
B Site Doping of PST 40/60
Mn doped PST. As a consequence the perovskite PST crystal is already slightly degraded
with a Mn content of 3 mol%, as it can be seen in Fig. 6.2.
120
It is quite interesting to note that the measured behaviour of Pb0.4Sr0.6Mn0.03Ti0.97O3
with negative bias is comparable to the theoretical one of Pb0.4Sr0.6Mn0.01Ti0.99O3.
Altogether the measured data fits better to the theoretical curves with positive bias.
Maybe that indicates a systematical error in the measurements.
However, the decrease in the oxygen vacancy concentration due to the generation of
higher valance Mn ions leads as well to a restraint domain pinning, and in turn to an
improvement of ferroelectric properties because oxygen vacancies are always considered
as the major pinning cause of ferroelectric domain wall motions [25]. The enhancement
of ferroelectric properties in Pb0.4Sr0.6MnxTi1-xO3 with increasing Mn content is shown in
Fig. 6.7.
-25
-6 -4 -2 0 2 4 6
Bias Voltage [V]
Fig. 6.7: Hysteresis loops of Pb0.4Sr0.6MnxTi1-xO3. The film is paraelectric with x=0 and the ferroelectricity improves with
x.
The polarisation-voltage hysteresis loop of pure PST 40/60 shows a typical paraelectric
behaviour – a straight line at room temperature. With increasing Mn content both the
pure
1%Mn
3%Mn
5%Mn