Synthesis of a polar ordered oxynitride perovskite

At a Glance

Metadata	Details
Publication Date	2017-06-30
Journal	Physical review. B./Physical review. B
Authors	Rajasekarakumar Vadapoo, Muhtar Ahart, Maddury Somayazulu, Nicholas Holtgrewe, Yue Meng
Institutions	Howard University, George Washington University
Citations	12
Analysis	Full AI Review Included

6CCVD Technical Analysis: Synthesis of Polar Ordered Oxynitride Perovskite ($\text{YSiO}_2\text{N}$)

This document analyzes the technical requirements and achievements of the high pressure-temperature (HPHT) synthesis of polar ordered $\text{YSiO}_2\text{N}$ perovskite, connecting the critical material needs—specifically ultra-high purity, optical-grade Single Crystal Diamond (SCD) components—directly to 6CCVD’s core capabilities in MPCVD diamond fabrication.

Executive Summary

The synthesis of the novel polar ordered oxynitride perovskite $\text{YSiO}_2\text{N}$ represents a significant breakthrough in materials science, driven by extreme pressure and temperature techniques utilizing Diamond Anvil Cells (DACs).

Novel Material Synthesis: First successful synthesis of a polar ordered oxynitride perovskite ($\text{YSiO}_2\text{N}$), previously only predicted via Density Functional Theory (DFT).
High Performance Prediction: DFT predicts a giant spontaneous polarization of 130 $\text{mC}/\text{cm}^2$ and very large nonlinear optical (NLO) coefficients, positioning $\text{YSiO}_2\text{N}$ as a prime candidate for next-generation optoelectronic devices.
Methodology Reliance on Diamond: Synthesis utilized DACs combined with in-situ double-sided laser heating (LH) at extreme conditions (up to 13 GPa and >1,500 K).
Polarity Confirmation: The material was experimentally confirmed to be polar and non-centrosymmetric via strong Second Harmonic Generation (SHG) observed using a 1,064 nm Nd: YAG laser.
Structural Verification: X-ray Diffraction (XRD) confirmed the tetragonal structure (P4mm space group) and the high c/a ratio (1.34), providing strong evidence for successful Oxygen/Nitrogen (O/N) anion ordering.
Critical Material Requirement: The success of this HPHT technique is fundamentally dependent on the exceptional optical clarity, thermal stability, and mechanical strength of high-purity Single Crystal Diamond (SCD) anvils.

Technical Specifications

Extracted quantitative data points regarding the material properties and experimental parameters.

Parameter	Value	Unit	Context
Predicted Spontaneous Polarization	130	mC/cm²	DFT prediction for YSiO₂N
YSiO₂N Synthesis Temperature	> 1,500	K	Achieved via double-sided laser heating in DAC
Synthesis Pressure (Initial)	13	GPa	Estimated initial pressure in the DAC chamber
Synthesis Pressure (Quenched)	10	GPa	Pressure maintained during subsequent XRD measurements
Minimum Phase Formation Pressure	4	GPa	Lowest pressure where the new phase formed
YSiO₂N Lattice Parameter (a)	3.234(5)	Å	Observed @ 10 GPa, Space Group P4mm
YSiO₂N Lattice Parameter (c)	4.339(5)	Å	Observed @ 10 GPa
Structural c/a Ratio	1.34	Dimensionless	High ratio confirms O/N anion ordering and perovskite distortion
Raman Excitation Wavelength	532	nm	Used in backscattering geometry
SHG Excitation Wavelength	1,064	nm	Near IR, 8 ns to 20 ns pulsed Nd: YAG laser source
XRD X-ray Beam Spot Size	7 to 5	µm	Focused beam size for high-resolution diffraction
Dominant Raman Mode (Observed)	246	cm^-1	E(x,y) symmetry, key mode proving formation

Key Methodologies

The synthesis employed advanced HPHT techniques that rely on the optical transparency and mechanical robustness of the SCD components in the DAC system.

Reactant Preparation: Fine powders of parent yttrium nitride (YN) and amorphous silica ($\text{SiO}_2$) were ground and handled in an inert argon atmosphere to prevent reaction with air/moisture.
DAC Sample Loading: Reactants loaded into a Diamond Anvil Cell (DAC) using a stack geometry ($\text{SiO}_2$/YN/$\text{SiO}_2$) within a steel gasket, optimized to enhance solid-state diffusion. Ruby was used as the internal pressure standard.
Simultaneous HPHT Application: High pressure (up to 13 GPa) and high temperature (>1,500 K) achieved concurrently using an online double-sided laser heating system.
Laser Heating Parameters: A 1.06 µm Nd: YLF fiber laser was focused to a small heating spot (30 µm). Temperatures were determined by fitting the Planck radiation function to the thermal emission collected from the heated sample.
In-situ/Ex-situ Structural Characterization: Synchrotron X-ray diffraction (XRD) was performed at high-energy light sources (APS, DESY) using a highly focused X-ray beam (5-7 µm).
Raman Spectroscopy: Conducted in a backscattering setup using a 532 nm laser, requiring high optical quality diamond windows for signal integrity.
Second Harmonic Generation (SHG): Polarity confirmed by subjecting the quenched sample (at 11 GPa) to a 1,064 nm pulsed Nd: YAG laser, demonstrating a very strong SHG signal.

6CCVD Solutions & Capabilities

This research highlights the necessity of exceptionally high-quality SCD materials capable of withstanding extreme mechanical, thermal, and optical loads. 6CCVD is uniquely positioned to supply and engineer the required diamond components to replicate or scale this research.

Applicable Materials for Research Replication/Scaling	6CCVD Service Offering	Technical Advantage & Sales Driver
High-Purity Single Crystal Diamond (SCD)	DAC Anvils and Windows	Our MPCVD SCD is grown with ultra-low nitrogen incorporation, providing superior optical transparency necessary for precise in-situ laser heating (1.06 µm) and spectroscopic analysis (532 nm Raman, SHG). We offer SCD up to 500 µm thick.
HPHT Component Reliability	Custom Dimensions and Substrates	We manufacture SCD plates/wafers up to 125 mm and substrates up to 10 mm thickness. This ensures engineers can fabricate highly robust DAC anvils capable of maintaining stability under loads exceeding 13 GPa and temperatures >1,500 K.
Advanced Polarity and NLO Devices	Precision Polishing	DAC results depend on the flatness and parallelism of the anvils. 6CCVD guarantees SCD surface roughness (Ra) of < 1 nm, reducing light scatter and ensuring uniform pressure distribution crucial for crystallization.
Future Thin Film Implementation	Custom Boron-Doped Diamond (BDD) Wafers	If the resulting polar YSiO₂N is integrated into ferroelectric or piezoelectric thin film devices, conductive substrates are often required. 6CCVD provides heavy BDD films with tunable electrical properties and exceptional mechanical hardness.
Micro-Fabrication and Integration	Laser Cutting and Metalization	We offer precise laser cutting services for custom anvil shapes and micro-optical components. Our in-house metalization capability (Au, Pt, Pd, Ti, W, Cu) supports the development of future electrode structures for NLO or ferroelectric prototypes based on $\text{YSiO}_2\text{N}$.
Engineering Consultation	In-House PhD Expertise	6CCVD’s technical team specializes in advising researchers on optimal material choice (orientation, impurity level, and polishing) to maximize performance in extreme environments, whether for Nonlinear Optical or HPHT synthesis projects.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

For decades, numerous attempts have been made to produce polar oxynitride\nperovskites, where some of the oxygen are replaced by nitrogen, but a polar\nordered oxynitride has never been demonstrated. Caracas and Cohen studied\npossible ordered polar oxynitrides within density functional theory (DFT) and\nfound a few candidates that were predicted to be insulating and at least\nmetastable. YSiO2N stood out with huge predicted polarization and nonlinear\noptic coefficients. In this study, we demonstrate the synthesis of\nperovskite-structured YSiO2N by using a combination of a diamond anvil cell and\nin-situ laser heating technique. Subsequent in-situ X-ray diffraction, second\nharmonic generation, and Raman scattering measurements confirm that it is polar\nand a strong nonlinear optical material, with structure and properties similar\nto those predicted by DFT.\n

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Original Source

DOI: https://doi.org/10.1103/physrevb.95.214120