ISSN 10637397, Russian Microelectronics, 2013, Vol. 42, No. 8, pp. 463–466. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © D.V. Roshchupkin, D.V. Irzhak, E.V. Emelin, R.R. Fakhrtdinov, O.A. Buzanov, S.A. Sakharov, 2012, published in Izvestiya Vysshikh Uchebnykh Zavedenii.
Materialy Elektronnoi Tekhniki, 2012, No. 3, pp. 25–28.
The development of modern acoustoelectronics is
associated with the search for new promising piezo
electric crystals possessing good thermal properties
and high piezoelectric constants. In the past decade,
new piezoelectric materials from the group of lantha
num–gallium silicate (langasite) are actively sought.
Crystals of this group possess point symmetry group 32
similarly to the SiO
crystal of piezoquartz and good
thermal stability [1–4]. Electromechanical coupling
coefficients for the crystals of this group are worse than
those of LiNbO
crystals but substantially surpass the
corresponding values for quartz crystals. We previously
investigated in detail the acoustic properties of crystals
of langasite La
(LGS) [5–7] and langatate
(LGT) , which are now the base
materials in the fabrication of hightemperature sen
sors based on surface acoustic waves (SAW). It should
be noted that interest in crystals of the langasite group
is also associated with the absence of phase transitions
in these crystals up to the melting point.
More than 250 crystals can be potentially synthe
sized in the langasite group. These are not only quater
nary LGS and LGT crystals but also quinary crystals
(LGTA) and Ca
Below we present the examples of the synthesis of
the quinary crystal of the group lanthanum–gallium
silicate by the Czochralski method and the subsequent
investigation of the structural perfection and acoustic
properties of the obtained crystals with the help of lab
oratory and synchrotron Xray radiation sources using
highresolution Xray diffractometry and topography.
SYNTHESIS OF THE CRYSTALS
OF THE GROUP
OF LANTHANUM–GALLIUM SILICATE
The melting point of the crystals of the group of
lanthanum–gallium silicate, depending on the crystal
composition, lies in the range of 1300–1500°C. The
crystals are synthesized by the Czochralski method.
The starting charge for the crystal growth is obtained
by the solidphase synthesis.
Figure 1 represents the LGTA, Czochralski
grown, crystal with induction heating of the crucible.
Iridium was selected as the crucible material. The cru
cible was cylindershaped with a diameter equal to the
crucible height. The LGTA crystal was grown in pure
argon, in which it is not possible to suppress thermal
decomposition and evaporation of gallium oxides
from the melt surface, which leads to the deviation of
the melt from stoichiometry. The melting of the start
ing charge and crystal growth were performed in a pro
Promising Materials of Acoustoelectronics
D. V. Roshchupkin
, D. V. Irzhak
, E. V. Emelin
, R. R. Fakhrtdinov
O. A. Buzanov
, and S. A. Sakharov
Institute of Microelectronic Technology and HighPurity Materials, Russian Academy of Sciences,
ul. Institutskaya 6, Chernogolovka, Moscow oblast, 142432 Russia
OAO Fomos Materials, ul. Buzheninova 16, Moscow, 105023 Russia
—The results of the investigation of multicomponent piezoelectric crystals of the group of gallium–
lanthanum silicate (langasite) are presented. The synthesis processes and the structure of crystals are investi
gated. The acoustic properties of the crystals are investigated using Xray topography and diffractometry. The
possibility of applying these piezoelectric crystals in hightemperature sensor devices based on surface acous
tic waves is shown.
: piezoelectric crystals, surface acoustic waves, bulk acoustic waves, Xray topography, Xray diffrac
LGTA crystal Czochralskigrown along growth