Determination of the thermal expansion coefficients of rare-earths scandates by X-ray diffraction
P. Veřtát1, J. Drahokoupil2
1Department of Solid State Engineering, FNSPE CTU in Prague, Trojanova 13, 120 00, Prague 2, Czech Republic
2Department of Advanced Structural Materials, Institute of Physics AS CR, Na Slovance 2, 182 21 Prague 8, Czech Republic
vertapet@fjfi.cvut.cz
The evolution on the field of advanced electronics is based on the intensive research of new materials with special electric and magnetic features. Great example of these materials is the group of the rare-earth orthoscandates belonging to the materials with the perovskite structure. These materials can be used e.g. as the substrate for the epitaxial thin films of the other perovskites, which may lead to their stronger ferroelectric behaviour and higher paraelectric transition temperature [1].
In our work we focus on the determination of the linear thermal expansion coefficients of rare-earth scandates SmScO3, TbScO3 and DyScO3 from monocrystalline samples by X-ray diffraction. Measurements on the monocrystals are extremely useful because this is the form in which the materials are applied. Lattice parameters of the samples were determined at different temperatures using the Panalytical X’Pert Pro diffractometer. For temperature regulation the Peltier module has been used allowing us to study the samples in the temperature interval from 25 °C to cca 70 °C.
To obtain precise data a new diffraction profile fitting program based on more complex and realistic knowledge of the X-ray emission spectra [2] has been created.
Determined thermal expansion coefficients of the samples are shown in tab. 1 in comparison with the known values of already measured rare-earth orthoscandates from polycrystalline measurements (text in italics). Expected linearity in the measured data has been observed (example shown in fig. 1, 2) showing that linear thermal expansion coefficients are sufficient enough to describe behaviour of these materials in our temperature intervals.
Table 1. Linear thermal expansion coefficients of the rare-earth orthoscandates
|
latt. parameter \ γ [10-6K-1] |
SmScO3 |
GdScO3 [3] |
TbScO3 |
DyScO3 |
DyScO3 [3] |
|
a |
5,9 |
5,9 |
6,7 |
5,7 |
5,7 |
|
b |
8,3 |
11,5 |
7,8 |
8,0 |
8,6 |
|
c |
9,6 |
14,5 |
8,4 |
9,5 |
11,0 |
|
|
|
Figure 1. Observed linear trend for the thermal expansion of the lattice parameter a in SmScO3 |
Figure 2. Observed linear trend for the thermal expansion of the lattice parameter c in DyScO3 |
