Lu Li

The electric and temperature fields formed in the furnace water system by electrodes of different shapes differ to some extent when the immersed high-voltage electrode boiler is in operation. To obtain the distribution of electric and temperature fields in the furnace water when different shapes of electrodes are used in a high-voltage electrode boiler, simulation models of spherical electrodes, planar electrodes, and tangential electrodes are established, respectively. The effects of the electrode structure on the electric and temperature fields in the furnace water were investigated. The simulation results show that the electric field distribution and temperature field distribution of the spherical electrode in the furnace water are the best among the three electrode structures. Meanwhile, in order to verify the accuracy of the adopted simulation method, simulation and temperature rise tests were carried out on a small spherical electrode model under 400 V AC, and the simulation calculation results and the temperature rise test results at special points were compared. The difference between the simulation and test results is less than 3%, which proves the reasonableness of the method. The method can be used as a reference for the design of electrodes for immersed high-voltage electrode boilers, as well as the analysis of electric and temperature fields around the electrodes.

In this work, the effects of different sintering temperatures and TiO₂ concentrations on the dielectric properties of ZrO₂ and Nb₂O₅ pre-doped CaCu₃Ti₄O₁₂ (CCTO) ceramics were investigated. These doped ceramics were sintered at temperatures of 1020, 1030, and 1040 °C, exhibiting the lowest dielectric loss of 0.01, which consistently remained below 0.03 across a wide frequency range from 10 to 10⁵ Hz. Simultaneously, they maintained a high dielectric constant of more than 3000 and remarkably met the requirements for an X8P capacitor (Δε′ ≤ ±10% at temperature range from −55 to 150 °C). It was clarified that TiO₂ doping increased grain boundary resistance, leading to the reduced dielectric loss, and elevated the grain boundary activation energy, thereby enhancing the temperature stability. The TiO₂-doped CCTO-based ceramics also demonstrated reduced sensitivity to variations in sintering temperature, highlighting their excellent manufacturability. This characteristic holds great promise for the fabrication of CCTO-based ceramics, which usually exhibit poor repetitiveness.