Crystallization of zirconia based thin films

Area of Science:

• Materials Science
• Ceramics Engineering
• Thin Film Technology

Background:

• Yttria-stabilized zirconia (YSZ) is crucial for various applications due to its unique properties.
• Understanding the crystallization kinetics of amorphous YSZ thin films is essential for controlling their microstructure and performance.
• Pulsed laser deposition (PLD), spray pyrolysis, and dc-sputtering are common methods for YSZ thin film fabrication.

Purpose of the Study:

• To investigate and compare the crystallization kinetics of amorphous 3YSZ and 8YSZ thin films prepared by different deposition techniques.
• To determine the critical temperatures and timeframes for the crystallization of YSZ thin films.
• To analyze the phase transformations and microstructural evolution during heat treatment.

Main Methods:

• Amorphous 3YSZ and 8YSZ thin films were deposited using pulsed laser deposition (PLD), spray pyrolysis, and dc-magnetron sputtering.
• Ex situ and in situ X-ray diffraction (XRD) were employed to monitor crystallization.
• Heat treatments were performed up to 1000 °C at various heating rates.

Main Results:

• A minimum crystallization temperature of 275 °C was observed for amorphous 3YSZ films grown by PLD, completing crystallization within five hours.
• Above 325 °C, PLD-grown 3YSZ films exhibited near-instantaneous crystallization with high micro-strain, forming the t'' phase.
• The t'' phase transformed to the t' phase above 600 °C upon micro-strain relaxation.
• 8YSZ films grown by PLD crystallized around 300 °C, significantly faster than those from spray pyrolysis and sputtering, which required heating to 800 °C at 2.4 K min⁻¹.

Conclusions:

• The deposition method significantly influences the crystallization kinetics and phase evolution of YSZ thin films.
• PLD enables rapid crystallization of YSZ thin films at relatively low temperatures.
• The observed phase transformations (t'' to t') are linked to micro-strain relaxation during annealing.