High-Tc Superconductivity in some Heavy Rare-earth Iron-arsenide REFeAsO1-delta(RE = Ho, Y, Dy and Tb) Compounds

New iron-arsenide superconductors of REFeAsO1-delta (RE = Ho, Y, Dy and Tb) were successfully synthesized by a high pressure synthesizing method with a special rapid quenching process, with the onset superconducting critical temperatures at 50.3 K, 46.5 K, 52.2K and 48.5 K for RE = Ho, Y, Dy and Tb respectively.