TY - JOUR

T1 - Phenomena and mechanisms of mixed crystal formation in solutions I. General concept on the example of the system KHC8H4O4-RbHC8H4O4 -H2O

AU - Glikin, A. E.

AU - Kovalev, S. I.

AU - Rudneva, E. B.

AU - Kryuchkova, L. Yu

AU - Voloshin, A. E.

N1 - Funding Information: The authors express their gratitude for financial support to the INTAS—European Community (project 99-0247); DAAD—Germany; Russian Fund for Basic Research (grants 01-02-17350, 01-05-64912); Russian Fund for Assistance Domestic Science. The authors thank Prof. A.A. Chernov, Prof. A. Putnis and Prof. H. Klapper for discussions as well as Dr. L. Atkinson and Dr. A. Bromley for help in the preparation of the manuscript.

PY - 2003/7

Y1 - 2003/7

N2 - A comprehensive study of crystal morphology and imperfections in the isomorphic series potassium acid phthalate-rubidium acid phthalate (KAP-RbAP) in aqueous solutions was conducted using a general model of the processes of mixed crystal formation in solutions discussed earlier by the authors on experimental and theoretical basis. The system was chosen as a model to interpret basic processes. The utilization of both substances as well as their solid solutions was taken into account. Interaction between RbAP or KAP crystals and aqueous solutions saturated with either KAP or RbAP or both, in ratios varying from 10 to 90wt% (the step was about 10wt%), has been studied. All the processes were observed in situ and ex situ by optical microscopy and X-ray topography (Lang method). Solubilities of KAP and RbAP mixtures in water were determined and compositions of corresponding solid solutions were estimated for the isotherms 29°C and 39°C. These indicated a considerable convex curvature in concentration Schreinemakers diagrams. The main peculiarity of crystals is their having heteroepitaxial porous or uniform textures, which occur due to the secondary volume deficit or excess at the exchange reaction between a crystal and solution. In turn, the primary/secondary volume ratio depends on the solubilities of the components in the system (unconnected with the molar volumes of the substances) determined directly from Schreinemakers diagrams. The convexity of the KAP-RbAP solubility isotherms displays specific crystal formation in this system compared with features of Co-Ni Tutton salts whose isotherms have small curvatures. Firstly, this appeared as a shift from volume-deficit replacement toward volume-excess replacement. This resulted in non-uniform heteroepitaxial textures and sharp slowing down of the process at an intermediate stage. Phenomena occurring in such peculiar systems and interactions between the crystals and solutions of intermediate compositions have not been investigated before. The results obtained became a basis for developing a theory of mixed crystal formation in solutions. Optically transparent mixed monocrystals containing about 3 and 5-10wt% RbAP were isolated from solutions having the KAP/RbAP ratios of components 90/10 and 80/20wt%.

AB - A comprehensive study of crystal morphology and imperfections in the isomorphic series potassium acid phthalate-rubidium acid phthalate (KAP-RbAP) in aqueous solutions was conducted using a general model of the processes of mixed crystal formation in solutions discussed earlier by the authors on experimental and theoretical basis. The system was chosen as a model to interpret basic processes. The utilization of both substances as well as their solid solutions was taken into account. Interaction between RbAP or KAP crystals and aqueous solutions saturated with either KAP or RbAP or both, in ratios varying from 10 to 90wt% (the step was about 10wt%), has been studied. All the processes were observed in situ and ex situ by optical microscopy and X-ray topography (Lang method). Solubilities of KAP and RbAP mixtures in water were determined and compositions of corresponding solid solutions were estimated for the isotherms 29°C and 39°C. These indicated a considerable convex curvature in concentration Schreinemakers diagrams. The main peculiarity of crystals is their having heteroepitaxial porous or uniform textures, which occur due to the secondary volume deficit or excess at the exchange reaction between a crystal and solution. In turn, the primary/secondary volume ratio depends on the solubilities of the components in the system (unconnected with the molar volumes of the substances) determined directly from Schreinemakers diagrams. The convexity of the KAP-RbAP solubility isotherms displays specific crystal formation in this system compared with features of Co-Ni Tutton salts whose isotherms have small curvatures. Firstly, this appeared as a shift from volume-deficit replacement toward volume-excess replacement. This resulted in non-uniform heteroepitaxial textures and sharp slowing down of the process at an intermediate stage. Phenomena occurring in such peculiar systems and interactions between the crystals and solutions of intermediate compositions have not been investigated before. The results obtained became a basis for developing a theory of mixed crystal formation in solutions. Optically transparent mixed monocrystals containing about 3 and 5-10wt% RbAP were isolated from solutions having the KAP/RbAP ratios of components 90/10 and 80/20wt%.

KW - A1. Phase diagrams

KW - A1. Solid solutions

KW - A1. Volume defects

KW - A3. Topotaxy

KW - B1. Metalorganic compounds

UR - http://www.scopus.com/inward/record.url?scp=0038717093&partnerID=8YFLogxK

U2 - 10.1016/S0022-0248(03)01189-8

DO - 10.1016/S0022-0248(03)01189-8

M3 - Article

AN - SCOPUS:0038717093

VL - 255

SP - 150

EP - 162

JO - Journal of Crystal Growth

JF - Journal of Crystal Growth

SN - 0022-0248

IS - 1-2

ER -