Densification and fine-grain formation mechanisms of BaTiO3 ceramics consolidated by self-assembly sintering

Abstract

In this paper, from the perspective of thermodynamics and kinetics, we have studied the mechanism of balancing the densification and grain growth via co-sintering the micron and nano powders, also known as self-assembly sintering. In the experiment, the 200 nm and 80 nm BaTiO3 spherical powders were used as models for combination and co-sintering. In terms of thermodynamics, the contact angle method is applied to determine the free energy of the binary particle size system. The surface free energy of 200 nm and 80 nm BaTiO3 powders are 51.66 J/mol and 203.47 J/mol, respectively. When the powder ratio is 1:1, the surface free energy of the binary particle size system is 127.56 J/mol, which is the reason for the balance between densification and grain growth. In terms of kinetics, the Arrhenius equation was utilized to calculate the apparent activation energy (Q) of the binary particle size system. The results show that the value of Q is 360 kJ/mol at 1000 °C. The fine-grained ceramics with high relative density obtained by this sintering method at a low sintering temperature (1000 °C) can be explained by the relative low value of Q.

Near-Infrared Shielding Performance of Tungsten-Doped Tin Dioxide Nanoparticles

“…Figure exhibits the XRD patterns of nano-WTO powders calcined at 800 °C under hydrothermal conditions of 180 °C with different doping amounts of tungsten (0, 1, 3, 5, and 7%), and the diffraction peaks gradually widened as the doping amount of tungsten increased. The result indicates that the grain size gradually reduces because the pinning effect of tungsten atoms entering the grain boundary of tin dioxide hinders the movement of the grain boundary, which ultimately inhibits the growth of the grain. , At the same time, due to the severe lattice distortion caused by the high doping amount, the Gibbs free energy that causes the grain growth is weakened, and the grain size is reduced. − It can also be seen from Figure that the diffraction peaks of different angles have different intensities, in which the diffraction peak on the (110) plane is sharper than those on other crystal planes, indicating that the grain of WTO powder grows along the (110) plane preferentially under this condition. In addition, tungsten doping can effectively inhibit the growth of SnO 2 matrix particles because the impurity ions entering the matrix can form a segregation layer on the surface of the matrix particles, thus effectively reducing the total energy of the system. , …”