No abstract

La/Mn codoped BaTiO 3 ceramics with various La 2 O 3 content, ranging from 0.3 to 1.0 at% La, were investigated regarding their microstructure and dielectric properties. The content of MnO 2 was kept constant at 0.01 at% Mn in all samples. La/Mn codoped and undoped BaTiO 3 were obtained by a modified Pechini method and sintered in air at 1300 0 C for two hours. The homogeneous and completely fine-grained microstructure with average grain size from 0.5 to 1.5m was observed in samples doped with 0.3 at% La. In high doped samples, apart from the fine grained matrix, the appearance of local area with secondary abnormal grains was observed. The dielectric properties were investigated as a function of frequency and temperature. The dielectric permittivity of the doped BaTiO 3 was in the range of 3945 to 12846 and decreased with an increase of the additive content. The highest value for the dielectric constant at room temperature ( r = 12846) and at the Curie temperature ( r = 17738) were measured for the 0.3 at% La doped samples. The dissipation factor ranged from 0.07 to 0.62. The Curie constant (C), Curie-Weiss temperature (T 0 ) and critical exponent () were calculated using the Curie-Weiss and the modified Curie-Weiss law. The highest values of Curie constant (C=3.2710 5 K) was measured in the 1.0 at% La doped samples. The obtained values for  ranged from 1.04 to 1.5, which pointed out the sharp phase transformation from the ferroelectric to the paraelectric phase.

No abstract

No abstract

In this paper the results of modeling and simulation of radiation stress effects in p-channel power VDMOSFET transistor have been presented. Based on measured results, the threshold voltage shifts as a function of absorbed dose and gate voltage during radiation stress have been modeled and implemented in the PSPICE model of the IRF9520 transistor. The transfer characteristics of the transistor are simulated and compared to the experimental ones. Difference is in the range 0.16% to 23.35% which represents a good agreement.