Find in Library

This study investigated the causes of microstructural changes and the resultant electrical properties according to the sintering temperature of 0.96(K_0.46−xNa_0.54−x)Nb_0.95Sb_0.05O₃-0.04Bi_0.5(Na_0.82K_0.18)_0.5ZrO₃ lead-free ceramics by analyzing the correlation between vacancy concentrations and 2D nucleation. When sintered for 4 h, no grain growth occurred for the x = 0.000 composition over a wide temperature range, demonstrating that the existence of initial vacancies is essential for grain growth. As x increased, that is, as the vacancy concentration increased, the critical driving force (ΔG_C) for 2D nucleation decreased, and abnormal grain growth was promoted. The number and size of these abnormal grains increased as the sintering temperature increased, but at sintering temperatures above 1100 °C, they decreased again owing to a large drop in ΔG_C. The x = 0.005 specimen sintered at 1085 °C exhibited excellent piezoelectric properties of d₃₃ = 498 pC/N and k_p = 0.45 due to the large number of large abnormal grains with an 83% tetragonal phase fraction. The x = 0.000 specimen sintered at 1130 °C with suppressed grain growth exhibited good energy storage properties because of its very high relative density and small grain size of 300 to 400 nm.