Reaction processes in a ZnO + 1%Gd2O3 powder mixture during mechanical and laser processing

X-ray diffraction, electron paramagnetic resonance, Fourier transform infrared spectroscopy and scanning electron microscopy were used to study the defect formation and reaction processes in a ZnO + 1%Gd2O3 powder mixture during its mechanical and laser processing. Mechanical treatment of the ZnO + 1%Gd2O3 powder mixture leads to a grinding of initial ZnO particles and formation of three types of superficial paramagnetic donor defect centers. The rise of the sample temperature with increasing processing time promotes a successive annealing of ZnO defects with small activation energies and of superficial defects in Gd2O3. The formation of a ZnO:Gd3+ solid solution in the used mechanical processing regimes has not been observed. Laser surface melting of the ZnO + 1%Gd2O3 pellets provokes formation of a surface layer exhibiting a texture. The crystallization directions in the superficial layers of different specimens have a random character. In the superficial layers and deep sub-surface layers, processes of solid-state interactions (formation of an inhomogeneous ZnO:Gd3+ solid solution) take place. The surplus charges of the Gd3+ ions are compensated by the formation of Zn vacancies or interstitial oxygen ions which in the laser-surface-melted layers are located closer to the Gd3+ ions than in the case of single-crystalline samples.

► Mechanical and laser processing of ZnO + 1%Gd2O3 powder mixture.
► Evolution of defect formation during mechanical treatment.
► Surface texturing during laser surface melting.
► Formation of an inhomogeneous ZnO:Gd3+ solid solution.