Structure-Property Relations in Sol-Coated PMN Ceramics: Microscopy, Dielectric and Electromechanical Response
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287 Mat. Res. Soc. Symp. Proc. Vol. 606 C 2000 Materials Research Society
5°C/min to burnout the organics. The samples are kept for 2 hours at 600'C and then cooled by furnace cooling. The sintering is done by using a double crucible method with a PbZrO 3 lead source powder. The sintering of samples is done at 1200'C. The system is heated at 5°C/min and kept at 1200'C for 4 hours. It is then cooled with furnace cooling. The samples are then polished as necessary for the characterization methods. The sintered samples are electroded by Ag/Pt sputtering and Ag electroding paste for electronic and electromechanical measurements. The dielectric measurements are done in a system that includes a Delta 9039 furnace, a HP 3488A Switch/Control Unit and a HP 4284A Precision LCR Meter. A program written using Lab View by National Instruments controls the whole system. The samples are heated to 160'C with a ramp of 10°C/min and held at that temperature for 5 minutes until the system equilibrates. Then they are cooled with a rate of 2°C/min by using liquid nitrogen. The data is taken during cooling until -40'C at 4 different frequencies; 0.1,1,10 and 100 kHz. The electromechanical measurements are done as discussed in Cho et al. (1Hz, ±+MV/m) 5 . The X-ray Diffraction measurements are done by using Bragg Brentano Parafocusing Powder Diffractometer. The Cu-Kct x-ray is generated with a voltage of 40kv and current of 20mA. The effect of other emissions is filtered using the program Jade. For the grain size measurements an AMRAY 1810 Scanning Electron Microscope is used. The TEM study is done by using JOEL-Jem 2000 FX Transmission Electron Microscopy. The EDS detector used is a PGT-Prism Light Element X-ray detector. RESULTS: i) Diffraction The measurements are done by using the X-ray diffraction machine described before. All measurements are done between 20 and 120 degrees 20 with 0.02 step size, 7 sec count time. Si is used as an internal standard. The following graph (Figure 1) shows the effect of composition change on lattice parameters. The standard deviation bars are for the machine error and calculated by the program Jade. In samples T4 and T8 a second phase of Pb2 Nb2 TiO9 , which is accepted as a pyrochlore with Z=4, forms This phase is not observed in T2.The main peak for this phase can be seen in figure 2 Lattice
parameters
4,038
. 4.036 4.034
I
4.032 4,03
S4.028 4.026 4.0240
2
4
6
a
10
Mo1% additlon
Figure 1: The lattice parameters for the sol-coated PMN-ceramics
Figure2: Main peak of pyrochlore formed in Ti added samples 288
ii)ElectricallElectromechanical Response: The lkHz values of room temperature measurements of maximum. dielectric constant (Kmax), temperature (T@Kmax) and loss (tan8) at maximum dielectric constant are tabulated and then graphed. 5 samples for each composition are measured. To see the compositional effect on the properties the Student T-test is used. The following graphs (3, 4 and 5) are the final values for Kmax, T@Kmax and tan5. The confidence level between each data step is sh
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