Synthesis and Electrical Properties of Stabilized Manganese Dioxide (α‐MnO ₂ ) Thin‐Film Electrodes

Abstract

Manganese dioxide (α‐MnO 2 ) thin films have been explored as a cathode material for reliable glass capacitors. Conducting α‐MnO 2 thin films were deposited on a borosilicate glass substrate by a chemical solution deposition technique. High carbon activities originated from manganese acetate precursor, (Mn(C 2 H 3 O 2 ) 2 ·4H 2 O) and acetic acid solvent (C 2 H 4 O 2 ), which substantially reduced MnO 2 phase stability, and resulted in Mn 2 O 3 formation at pyrolysis temperature in air. The α‐MnO 2 structure was stabilized by Ba 2+ insertion into a (2 × 2) oxygen tunnel frame to form a hollandite structure. With 15–20 mol% Ba addition, a conducting α‐MnO 2 thin film was obtained after annealing at 600–650°C, exhibiting low electrical resistivity (∼1 Ω·cm), which enables application as a cathode material for capacitors. The hollandite α‐MnO 2 phase was stable at 850°C, and thermally reduced to the insulating bixbyte (Mn 2 O 3 ) phase after annealing at 900°C. The phase transition temperature of Ba containing α‐MnO 2 was substantially higher than the reported transition temperature for pure MnO 2 (∼500°C).