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Grain growth kinetics in 0.1 to 2 mol % B 2 O 3 -added ZnO ceramics was studied by using a simplified phenomenological grain growth kinetics equation G n = K 0 ·t·exp(−Q/RT) together with the physical properties of sintered samples. The samples, prepared by conventional ceramics processing techniques, were sintered at temperatures between 1050 to 1250°C for 1, 2, 3, 5 and 10 hours in air. The kinetic grain growth exponent value (n) and the activation energy for the grain growth of the 0.1 mol % B 2 O 3 -doped ZnO ceramics were found to be 2.8 and 332 kJ/mol, respectively. By increasing B 2 O 3 content to 1 mol %, the grain growth exponent value (n) and the activation energy decreased to 2 and 238 kJ/mol, respectively. The XRD study revealed the presence of a second phase, Zn 3 B 2 O 6 formed when the B 2 O 3 content was 1 mol %. The formation of Zn 3 B 2 O 6 phase gave rise to an increase of the grain growth kinetic exponent and the grain growth activation energy. The kinetic grain growth exponent value (n) and the activation energy for the grain growth of the 2 mol % B 2 O 3 -doped ZnO ceramics were found to be 3 and 307 kJ/mol, respectively. This can be attributed to the second particle drag (pinning) mechanism in the liquid phase sintering.

The effect of 0.5, 1.0, 2.0 mol% B 2 O 3 additions on the microstructure and densification of BaTiO 3 (Ba/Ti=0.98) + 0.0025 mol% Sb 2 O 3 were investigated. The BaTiO 3 powders were prepared by the conventional ceramic processing method. The samples were sintered at different temperatures between 1200 to 1360 o C for 1 hour. Generally, low temperature sintering of the TiO 2 excess compositions below the eutectic temperature of 1332 o C results in a characteristic platelettype grained microstructure. This platelet structure was found to be the Ba 2 Ti 5 O 12 phase in the undoped BaTiO 3 (Ba/Ti=0.98) and in the 0.5 mol% B 2 O 3 added samples sintered up to 1335 o C. Suppression of these platelet-type grains occurred in the B 2 O 3 additions above 0.5 mol%. A secondphase precipitate of boron containing compounds was not detected by XRD. The maximum theoretical density of 98% was obtained in the Sb 2 O 3 doped BaTiO 3 samples sintered at 1275 o C and in the 0.5 mol% B 2 O 3 added samples sintered at 1300 o C for 10 hours reaching the 96% T.D. The bulk densities of the sintered samples decreased with the increasing B 2 O 3 content due to the high porosity trapped between the grains.

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