A novel laser-processing technique that produces bulk YBa2Cu3Ox (1 2 3) plates has been developed. Through the application of a square CO2 laser beam with uniform energy density distribution to the surface of 1 2 3 powder compact, a single piece of ribbon-like plate is produced. This plate may be separated from the powder compact after laser scanning. The width of the plate is ≈ 6 mm, while its thickness is 0.1–0.2 mm. Powder X-ray diffraction indicates that laser-treated samples contain both orthorhombic and tetragonal 1 2 3 phases, as well as Y2O3 (2 0 0), Y2BaCuO5 (2 1 1), BaCuO2 (0 1 1), and CuO (0 0 1) phases. Scanning electron microscopy reveals a pattern of phase segregation along the transverse cross-section after solidification of the plate. After oxygen annealing of a single ribbon piece, Tc is found to be 90 K. This technique may be applicable to the mass production of 1 2 3 bulk superconductor by continuous melting of 1 2 3 powders. In addition to its potential for practical applications, the laser technique also helps to explain the complex phases and microstructure formation during melting and solidification of laser-melted 1 2 3 liquid. A model relating the microstructure to the thermal history inside the laser-affected region and to the phase diagram of incongruently melting 1 2 3 material has been developed to analyse phase formation during laser melting and solidification processes. Reasonable correspondence between theoretical analysis and experimental results was obtained.