LAB6-BASED, ZR-ALLOYED, DECORATIVE HARD COATINGS

Dark-violet hard coatings based on LaB6 are promising candidates for t he extension of the conventional spectrum of decorative coatings. A pr omising approach which can overcome certain application-related proble ms, such as brittleness and insufficient adhesion, involves the alloyi ng oi these coatings with suitable elements or compounds. This paper p resents some fundamental results on the structure and basic properties of LaB6-based coatings alloyed with zirconium, employing simultaneous sputtering from two planar magnetrons supplied with LaB6 and Zr targe ts. The characterization of the coatings was performed by scanning ele ctron microscopy, electron probe microanalysis and X-ray diffraction. The results are discussed in terms of the hardness and optical propert ies of the coatings expressed by the CIE-La*b* system La-Zr-B films o f varying composition were deposited using different magnetron current ratios for lit two targets used. The film hardness decreases from app roximately 2100 HV0.01 (LaB6-based coatings) to 500 HV0.003 (Zr-based coatings), which corresponds to an increase in the Zr concentration in the films and a gradual shift of the morphology from LaB6 through an amorphous phase to sigma- and omega-Zr. The brilliance values L are m ainly determined by the Zr concentration due to the increasing metalli c binding character within the coatings. The bluish colouration of the coatings decreases with increasing Zr concentration, whereas the redd ish hue is almost unaffected. Finally, the alloying of decorative hard coatings seems to be a promising technique for the optimization of th eir properties.