12.1 Introduction

There is a wide variety of technologically important oxide single crystals, which find applications in diverse fields. These are employed as laser hosts, in nonlinear optical devices, optical wave guides and other components in optical communications, in memories, and numerous other applications. Many of the oxide crystals had been extensively used as substrates to prepare high Tc superconductors, blue light emitting lasers, magnetic bubble memories, and so forth. Lithium niobate [1 2], cadmium tungstate, sapphire, ruby, garnets [3], lithium tantalate, lead molybdate [4], bismuth germanate, potassium niobate, barium titanate [5], bismuth silicate [6], and others are being extensively used for making important devices. We shall discuss recent advances in growth and structural characterization of lithium niobate and bismuth germanate (BGO) crystals.

Lithium niobate (LiNbO ₃) is an opto-electronic material. LiNbO ₃ crystals with high degree of perfection, optical homogeneity, correct stoichiometry, and single ferroelectric domain are required for fabrication of surface acoustic wave devices (SAW), optical wave guides, photonic switches in telecommunication, as piezoelectric materials in tomography, and as second harmonic generators (SHG) [1]. LiNbO ₃ single crystals have large electro-optic coefficients and do not need application of a high voltage. These crystals have received much attention as phase conjugate wave generators and real-time read-write holograms using the photorefractive effect [7]. Generally, to improve properties, LiNbO ₃ crystals have...