Synthesis, crystal structures and characterization of novel alkali-metal containing rare-earth orthoborates

Abstract

Inorganic metal borates are of research interest due to their structural diversity, interesting physico-chemical properties and wide applications in optics. To date, several rare-earth borates are developed as laser crystals, nonlinear optical crystals, self-frequency-doubling crystals, fluorescent phosphors and scintillation materials. In addition to these optical applications, rare-earth borates attract intensive attention on fascinating magnetic behaviors arising from their unpaired inner shell 4f electrons. Therefore, the design and search of new rare-earth borates and the investigation of their unique properties are of practical and scientific significance. This cumulative dissertation involves the use of solid-state synthesis and flux crystal growth methods for exploring the descriptive chemistry of various alkali metal-containing rare-earth borate systems where several new structures were isolated. In chapter 1, a series of typical and appealing alkali metal-containing rare-earth borates are reviewed in terms of their crystal structures, structural variation as well as their applications. Chapter 2 refers to the experimental methods and consists of two parts: synthesis methods of powder and single-crystal samples and multi-tool methods for a variety of characterization. Chapter 3 introduces a series of rare-earth orthoborates KLi2RE(BO3)2 (RE = Dy, Ho, Er, Tm, Yb and Y) with a new structure-type along with their detailed investigations of the optical, magnetic, vibrational, and thermal properties as well as DFT calculation. In chapter 4, the synthesis and crystal structures of novel alkali rare-earth orthoborates K3RE3(BO3)4 (RE = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) along with the structural relationship between the reported A3RE3(BO3)4 (A = Na, K, Rb) systems are discussed. The following chapter 5 describes a novel layered potassium praseodymium oxo-orthoborate K2Pr2O(BO3)2 with crystal structure, optical, magnetic, vibrational, and thermal properties. The last chapter 6 is the overall summary and the outlook of this cumulative thesis.