Growth Kinetics of the (110) Faces of Complex Potassium Cobalt–Nickel Sulphate K2CoxNi1−x(SO4)2·6H2O Crystals

Dmitry A Vorontsov,Ekaterina L Kim,Elena B Rudneva,Vadim V Grebenev,Vera L Manomenova,Alexey E Voloshin,Natalia A Vasilyeva

doi:10.3390/cryst11060642

Abstract

The normal growth rate, the steepness of polygonized growth hillocks and the velocity of step movement on the (110) faces of potassium cobalt–nickel sulphate crystals in aqueous solutions with cobalt to nickel ratios of 1:1 and 1:2 were investigated as a function of supersaturation by the geometry of growth hillocks using laser interferometry. It was found that the morphologies of growth hillocks on the (110) faces of the crystals grown from 1:1 and 1:2 solutions are similar and that the growth hillocks are formed by multiple screw dislocation sources. The experimental data on the growth kinetics of the (110) faces of the crystals were analyzed by using the Burton–Cabrera–Frank theory. It was found that (1) there is a critical supersaturation for the growth of the (110) faces, and the value of this supersaturation in the 1:2 solution is higher than that in the 1:1 solution, and (2) the kinetic coefficient of the step movement in the sectors of growth hillocks is highly anisotropic, and the values of this coefficient are larger in 1:2 solution than in 1:1 solution. These results are discussed in the presented work.

Highlights

This work is aimed to investigate by laser interferometry the morphology, growth kinetics and mechanism of the (110) faces of KCNSH over the supersaturation range in the solutions with the cobalt to nickel ratios equal to 1:1 and 1:2
After the seed KCNSH crystals had been put into a supersaturated solution, many polygonized growth hillocks appeared on the (110) face (Figure 1a)
We have confirmed by the Michelson laser interferometry that the (110)

Summary

Introduction

Study of the properties and growth process of the nickel and cobalt sulphate and complex potassium cobalt–nickel sulphate K2 Cox Ni1−x (SO4 )2 ·6H2 O (KCNSH) crystals is very important in connection with their application for the production of ultra-violet filters for modern devices based on the principles of the solar-blind technology [1,2]. The previous studies showed that K2 Co(SO4 )2 ·6H2 O (KCSH) [3] and K2 Ni(SO4 )2 ·6H2 O (KNSH) [4] crystals had a higher dehydration temperature than that of nickel sulphate hexahydrate crystals. The main drawback of simple nickel sulphate crystals is the existence of a transmission peak in the visible spectral region, which leads to lower sensitivity of the devices. The application of KCNSH crystals can help to solve this problem

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