Fabrication of single crystals has long been limited to melt-and solution-growth techniques. However, in recent years solid-state single crystal growth (SSCG) has appeared as a promising alternative to the conventional techniques due to its cost-effectiveness and simplicity in terms of processing. Moreover, the SSCG technique has enabled the fabrication of single crystals with complex chemical compositions and even incongruent melting behavior. A recently proposed mechanism of grain boundary migration known as the "mixed control mechanism" and the associated principles of microstructural evolution represent the basis of the SSCG technique. The mixed control mechanism has been successfully used to control the key aspects of the SSCG technique, which are the grain growth and the development of the microstructure during the conversion process of the single crystal from the polycrystalline matrix. This paper explains in brief basis of the mixed control mechanism and the underlying principles of microstructural evolution in polycrystalline materials and provides a comprehensive overview of the most recent research on single crystal materials fabricated via the solid-state single crystal growth technique and their properties.

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Latest advancements in transparent ceramics development have ensured a mainstream research interest in this family of materials. Crystallization of glass into transparent ceramics has emerged recently as an alternative but complementary trajectory for obtaining transparent ceramics, which circumvents some of the long-standing technical difficulties associated with traditional transparent ceramics processing. The full bulk glass crystallization allows for the synthesis of high-density/low-porosity transparent ceramics of stable and metastable phases or even non-cubic structures, which are difficult to obtain using the traditional processing methods. This article presents a brief survey of the science of the transparency of ceramics and a detailed overview of the materials systems and techniques used for the preparation of transparent ceramics through the glass crystallization route. Finally, the review provides authors' insights into the future trends and research directions aimed to encourage a widespread application of glass crystallization into transparent ceramics in the fabrication of next-generation materials.

Spinel-structured NiMn 2 O 4 ceramics, with different valence Ni sources, were originally prepared using Ni 2 O 3 and NiO as raw materials, and the effects of different valence Ni sources on their electrical properties were first investigated. XRD patterns show that both Ni 2 O 3 -based and NiO-based NiMn 2 O 4 ceramics are single cubic spinel structures. SEM/EDS images indicate that the NiMn 2 O 4 ceramics exhibited high density at the experiment-determined sintering temperatures. XPS results and Raman drifts prove that the Ni valence-induced changes in Mn ions at B sites played a significant role in the electrical properties and thermal stability of NiMn 2 O 4 ceramics. Compared with NiO-based NiMn 2 O 4 , the resistivity at 25°C (ρ 25°C ) of Ni 2 O 3 -based NiMn 2 O 4 increased dramatically from 3109 to 106958 Ω cm, the thermal constant (B 25/50 ) increased from 3264 to 4473 K, and the resistance shifts after annealing for 1000 h at 150°C decreased from 0.80% to 0.74%. The investigation of the relationship between the material properties and valence of Ni sources has provided a new and effective way for designing the spinel-structured negative temperature coefficient (NTC) materials by modulating the valence of ions at A sites in the raw materials. K E Y W O R D S electrical properties, Ni 2 O 3 , NiMn 2 O 4 , NiO, solid-state reaction Foundation of China (grant nos'.

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