New 100 K TlSr sub 2 (Ca,Cr)Cu sub 2 O sub 7 superconducting films

New TlSr{sub 2}(Ca,Cr)Cu{sub 2}O{sub 7} superconducting films on MgO(100) substrates have been prepared and characterized. The superconducting films were fabricated via a two-step process. Precursor SrCaCrCuO films were first deposited by spray pyrolysis at temperature of 350--400 {degree}C, and thallium was then incorporated by heating the precursor films between unfired TlSrCaCrCuO bulk pellets at 880--900 {degree}C in an oxygen atmosphere. The films were then cooled down to room temperature in an oxygen or argon atmosphere. The superconducting films were single 1212 phase with {ital c}-axis perpendicular to the surface of the MgO(100) substrates. Onset temperatures up to 110 K and zero-resistance temperatures up to 100 K were achieved. The critical transport currents ({ital J}{sub {ital c}}) of the films were about 7{times}10{sup 3} A/cm{sup 2} at 77 K.