This paper is devoted to the measurement results of piezoelectric, dielectric and elastic tensor components in the temperature range between 20• C and 400• C. It was revealed that excitation resonance and antiresonance signals were possible without preliminary sample polarizing. Besides, the sound velocities measured along the main axes by echo-pulse method at room temperature are presented. Key words: piezoelectric, dielectric, elastic constants, sound velocity PACS: 77.84Bismuth tellurite (BTO) single crystals are of piezoelectric material but their electromechanical properties have not been practically studied. In [1] there are some data concerning these properties in BTO. The coupling factor k 15 = 0.274 at room temperature presented in the work [2] is prospective enough to be used as the main elements of electromechanical transducers. This fact suggested us to continue studying these properties of Bi 2 TeO 5 . This paper presents the results of investigating the piezoelectric, dielectric and elastic properties of bismuth tellurite single crystals between 20• C and 400• C (besides the sound velocity vector components which were measured at room temperature). Bi 2 TeO 5 is a polar single crystal belonging to the Abm2 space group. It possesses the orthorhombic symmetry and the fluorite-type structure with the unit-cell parameters a = 11.602Å, b = 16.461Å, c = 5.523Å [5].Single crystals of BTO were grown using the Czochralski method. The melt was prepared from ultra high purity Bi 2 O 3 and TeO 2 at the ratio 47 and 53 mole % respectively just like in the work [4]. The crystal boules were cut along the main crystallographic axes in the form of plates and bars for corresponding coefficients. The cuts in the form of bars were executed in "a"-plane at the angles of 30• and 45• to "b"-axis. The sizes of the plates and bars were selected so as to excite the necessary vibrations. The plates were used to obtain d 15 and d 24 piezoelectric coc A

The dielectric constant ε and electron spin resonance spectra of Mn 2+ions have been studied in the range of the ferroelectric phase transition in Li 2 Ge 7 O 15 single crystals. Analysis of the experimental data permits one to estimate the critical exponents of dielectric susceptibility γ ∼ = 1.25, order parameter β ∼ = 0.32 and correlation length ν ∼ = 0.63. The values of the critical exponents determined in a fairly broad temperature interval around T c , are consistent with the theoretical predictions of the Ising model with a one-component non-polar ordering coordinate.