Lithium Niobate

Raw Material Preparation

High-purity Li₂CO₃ and Nb₂O₅ powders are weighed in the required stoichiometric ratio and thoroughly mixed. Proper composition control is critical to achieve desired electro-optical and ferroelectric properties.

Crucible Loading (Platinum Crucible)

The prepared charge is loaded into a platinum crucible, which is chemically stable and suitable for oxide crystal growth at high temperatures.

High-Temperature Melting

The charge is heated above the melting point (~1250°C) in a controlled furnace environment. A suitable atmosphere is maintained to minimise lithium evaporation and ensure melt stability.

Seed Crystal Introduction

A properly oriented LiNbO₃ seed crystal is slowly lowered into contact with the melt surface. Crystal orientation (typically Z-cut or specific axis) is selected based on application requirements.

Necking and Shoulder Formation

A thin neck is initially formed to improve crystal quality, followed by gradual diameter expansion (shoulder growth) to reach the desired crystal size.

Crystal Growth (Body Growth)

The crystal is pulled at a controlled rate with simultaneous rotation of the crystal and crucible. Stable thermal conditions are maintained to ensure uniform composition and avoid defects.

Tailing and Cooling

The crystal diameter is reduced toward the end to form a tail, and the crystal is separated from the melt. Slow and controlled cooling is essential to prevent thermal stress and cracking.

Cutting and Finishing

The grown boule is cut into wafers or required shapes, followed by grinding, lapping, and polishing. Final processing depends on applications such as modulators, waveguides, or piezoelectric devices.