Low-Dimensional Zero Thermal Expansion Enables Ultrastable Thermo-Optics in YAl₃(BO₃)₄ Single Crystal

Area of Science:

• Materials Science
• Solid-State Physics
• Crystallography

Background:

• Zero-thermal-expansion (ZTE) materials are crucial for thermal stability in devices.
• Traditional ZTE materials require stringent three-dimensional (3D) ZTE, limiting availability.
• A need exists for alternative strategies to achieve ZTE with broader material accessibility.

Purpose of the Study:

• To explore low-dimensional ZTE in single crystals.
• To demonstrate a new design strategy for ZTE materials.
• To investigate the thermo-optical performance of ZTE materials.

Main Methods:

• Utilizing ubiquitous bond rotations along specific crystallographic axes in framework structures.
• Characterizing the thermal expansion of trigonal YAl3(BO3)4 (YAB) crystal.
• Measuring the thermo-optical coefficient of YAB crystal within the ZTE temperature range.

Main Results:

• Achieved two-dimensional ZTE in YAB single crystals.
• Observed an ultralow thermal expansion coefficient of -0.02(7) MK⁻¹ within the ab plane (83–180 K).
• Demonstrated a significantly reduced thermo-optical coefficient variation (0.03(2) × 10⁻⁸ K⁻²) in the ZTE plane compared to conventional materials.

Conclusions:

• Established a new design strategy for functional ZTE materials through dimensionally confined effects.
• Highlighted the application potential of low-dimensional ZTE in precision optical and electronic devices.
• Relaxed the strict requirements for 3D ZTE, broadening the scope for ZTE material development.