Influence of temperature on the properties of Mn coatings electrodeposited from the electrolyte containing Te(VI) additive

The influence of the bath temperature on composition, current efficiency, structure, morphology, internal stresses and microhardness of Mn coatings obtained from manganese-ammonium sulphate electrolyte with 2.20 mM of Te(VI) additive at the current density of 15 A dm^?2 was investigated. It has been found that with rising of the bath temperature from 20 to 80 °C the current efficiency increases from 37 to 71 %, the total concentration tellurium in the deposits increases from 0.9 to 1.6 wt% and the average size of crystallites of the coatings declines approx. from 24 to 15 nm. The structure of Mn coatings changes from the mixture of α-Mn and β-Mn phases at the lower temperatures to α-Mn phase at higher temperatures. Large tensile stresses (from 76 to 106 MPa) were determined for the Mn coatings with the thickness of 1.5–2.0 μm obtained at the initial stage of the deposition process.