Magnetic measurements in a wide temperature range of several ternary LREBa2Cu3Oy samples differently doped by secondary phase nanoparticles of different sizes are analysed in terms of a thermally activated depinning process. Evolution of the involved parameters with temperature and particle size is discussed. Zr contamination of the secondary phase particles facilitates the particles size reduction during meltgrowth process up to nanometre scale. Critical current at low fields, facilitated by multiple vortex pinning, is inversely proportional to (a small power of) the mean particle size. With such defects both critical currents and irreversibility field are high enough for industrial applications up to 90.2K (boiling point of liquid oxygen).
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