Grain growth of ZnO nanocrystals synthesized in polyol medium with polyvinylpyrrolidone additives

In this work, we have investigated the influence of annealing temperature on the grain growth of zinc oxide nanocrystals synthesized in ethylene glycol and isothermally calcined at Ta: 300 °C, 500 °C, 700 °C for 60 min at the ambient atmosphere. The effect of polyvinylpyrrolidone (PVP) addition and annealing temperature on ZnO nanocrystal's phase composition, structural (scattering domain size of nanocrystallites L, unit lattice parameters a, c, and unit volume Vunit, theoretical density ρx) parameters, morphological (size, shape, specific surface area SSA) features, chemical composition, and grain growth kinetics were determined. It was found that Ta caused the increase in L of single-phase ZnO nanocrystals from 18 nm to 40 nm (with adding PVP) and to 45 nm (without adding PVP). Despite the surfactant composition, submicron grain sizes (D = 120-150 nm) were observed at Ta = 700 °C. The activation energy of grain growth was Q = 121.4 kJ/mol (without adding PVP) and Q = 126.4 kJ/mol (with adding PVP), while grain growth exponent was n = 1.9 (without adding PVP) and n = 2.0 (with adding PVP). ZnO nanocrystals annealed at 700 °C are forthcoming in the design of the active layers of solar cells, and at (300-500) °C are suitable for thermoelectric converters.