RESUMO
The heat capacity of two relaxors BaTi(1-x)Zr(x)O(3) (x = 0.35,0.40) was measured using adiabatic calorimetry in the temperature range 100-360 K. The C(p)(T) dependence of both compositions is characterized by the presence of two diffuse anomalies near the Burns temperature T(d) and the temperature of the maximum in permittivity T(m) in the temperature ranges 250-350 K and 120-200 K. The anomalous heat capacity near T(d) was analysed taking into account the distribution of Zr concentration in nanoregions leading to the distribution of their transition temperatures into the polar phase. Excess heat capacity near T(m) was discussed in the framework of the spherical random bond-random field model. The results are compared with the data obtained by the same procedures for PbMg(1/3)Nb(2/3)O(3) studied experimentally earlier.
RESUMO
The title compound, lead bismuth calcium sodium phosphate, Pb(4.6)Bi(0.4)Ca(2.6)Na(2.4)(PO(4))(6) crystallizes in the apatite structure type, with vacancies in sites 2a or 2b that are normally occupied by anions. The fact that the Bi and Pb ions are mainly localized in the 6h sites confirms the electron lone-pair influence on the apatite structure.
