Investigation into the Sensory Properties of Fine-Grain Polycrystalline Films Based on Cobalt, Nickel, and Praseodymium Oxides

Abstract

The changes in the electrical conductivity of thin films of cobalt, nickel, and praseodymium oxides in air and in media with a high concentration of ozone and argon are investigated. The surface morphology and the initial stages of formation of the films are analyzed. The samples prepared are examined using different physicochemical methods, such as X-ray powder diffraction and differential thermal analyses.

Physicochemical and Electrical Properties of Praseodymium Oxides

“…The above results are in agreement with data reported in [14], which pertain to crystalline films of PrO x synthesized by spray pyrolysis, using the hydrate nitrate (previously discussed) as the precursor salt.…”

“…Among the investigated precursors, for the synthesis of PrO x , the thermal decomposition of the nitrate salt [9,11,14] and the calcination of the hydroxide [9,15,16] have been already discussed in the present paper; remaining in the same ambit, studies have been focused also on the thermal decomposition of the carbonate, either as such, Pr 2 (CO 3 ) 3 • 8H 2 O, or after a reaction with citric acid (CA), which forms a complex with the metal ion [18]. Contrary to what happens in the case of the nitrate [11], the carbonate completely loses the water of crystallization in the temperature range between 25 • C and 152 • C. Subsequently, at about 435 • C, Pr 2 O 2 CO 3 is formed, and this species remains stable for about 70 degrees, prior to the evolution of CO 2 and the consequent formation of PrO 1.833 , behind 520 • C. As far as the Pr-CA complex is concerned, its stability seems to depend on the composition of the surrounding atmosphere: in the presence of a current of oxygen, the formation of PrO 1.833 is quantitative already at 450 • C; at this temperature, but in the presence of nitrogen or in air (static conditions), Pr 2 O 2 CO 3 is the major product (while heating in air, minor amounts of PrO 1.833 are also produced).…”