Crystal growth and concentration change of (Mn,Ni,Zn)-ferrite single crystals by the flame fusion method

Single crystals of (Mn,Ni,Zn)ferrite are grown by the flame fusion method. The chemical analysis of composition reveals that ZnO shows the largest change in concentration among the components, for example, from 26.7 mol% to 17.3 mol% in a crystal of 50 mm in length and 25 mm in diameter. This inhomogeneity is only observed along the growth direction and cannot be detected by analysis at this level of accuracy along the direction perpendicular to the growth direction, except at the periphery to a depth of 1 mm. This inhomogeneity may be explained as a result of the evaporation of Zn from the molten zone during growth. The equation $\text{C}{}_{\mathrm{o}}\text{C}\text{= 1 +}\text{K}\text{V}$ is derived (C /2b Zn concentration, V = crystal growth rate and C_o, K = const). Crystal free from cracks can be grown successfully by using an after-furnace made of SiC heater. A new apparatus to feed the crystal constantly with raw material powder is proposed, and by using this the change in concentration can be reduced to less than 1 mol% throughout the crystal of the above size. These crystals have also been investigated for the Micro-Vicker's hardness.