The mechanical and electrical properties in lanthanum
modified lead zirconate-titanate ceramics of 5/50/50 and 10/50/50 were
studied by mechanical loss Q - 1, Young's modulus E, electric
permittivity ε and tangent of dielectric loss of angle
tgδ measurements. The internal friction Q - 1 and Young modulus E measured from 290 K to
600 K shows that Curie temperature TC is located at 574 K and 435 K
(1st cycle of heating) respectively for ceramic samples 5/50/50 and
10/50/50. The movement of TC in second cycle of heating to lower
temperature (561 K for 5/50/50 and 420 K for 10/50/50) has been observed.
Together with Q - 1 and E measurements, temperature dependences of
ε=f(T) and tgδ=f(T) were determinated in temperature
range from 300 K to 730 K. The values of TC obtained during
ε and tgδ measurements were respectively: 560 K for
5/50/50 and 419 K for 10/50/50. These temperatures are almost as high as the
temperatures obtained by internal friction Q - 1 measurements in second
cycle of heating. In ceramic sample 10/50/50 the additional maximum on
internal friction Q - 1 curve at the temperature 316 K was observed