Effect of HPHT Treatment on Spectroscopic Features of Natural Type Ib-IaA Diamonds Containing Y Centers

Abstract

In this paper, we report a spectroscopic study of natural type Ib-IaA diamonds containing Y centers subjected to high-pressure high-temperature treatment at 7–7.5 GPa and 1700–2200 °C. Diamond samples showing the Y centers as the dominant absorption feature in the infrared spectra were selected from a collection of natural diamonds from alluvial placers of the northeastern Siberian Platform. The samples were investigated by spectroscopic techniques before and after each annealing stage. It was found that upon annealing at temperatures higher than 2000°C, the defect-induced one-phonon spectra changed from the Y centers to a new form with a characteristic band peaking at 1060 cm−1. Photoluminescence spectra of the samples were modified after each annealing stage starting from 1700 °C. The most significant changes in photoluminescence occurred at temperatures higher than 2000 °C and were associated with a sharp increase of the intensity of an emission band peaking at about 690 nm. A comparison with natural red-luminescing diamonds from Yakutian kimberlite pipes was performed. It was concluded that the observed 1060 cm−1 IR band and the 690 nm red emission band are genetically related to the Y centers and that defects or impurities responsible for the Y centers appear quite widespread in natural diamonds from various deposits worldwide.

IR Spectroscopy of Vacancy Clusters (Amber Centers) in CVD Diamonds Nanostructured by Fast Neutron Irradiation

“…The changes in the IR absorption spectra after annealing at temperatures above 1000 • C for samples D1 and D3 are shown in Figure 3a,b, respectively. The AC 4100 cm −1 absorption coefficient reaches α = 15 cm −1 for sample D3, which is an order of magnitude higher compared to that for the maximum AC absorption reported for natural diamonds [23][24][25][26][27][28][29][30][31][32][33]. The AC absorption for sample D1 is about three times lower than for D3; this ratio roughly corresponds with the neutron fluence ratio.…”

“…For the sample D3, the 4100 cm −1 band magnitude exceeds that for the two-phonon band (Figure 1b). Based on the 4100 cm −1 band position, shape and evolution with annealing, it can be associated with AC defects [23][24][25][26][27][28][29][30][31][32][33]55]. In the virgin unirradiated samples, CH x bands (2800-3000 cm −1 ) of the bonded hydrogen, presumably located at the grain boundaries, are detected (see bottom spectrum in Figure 1a), as well as a structureless absorption due to the inclusion of amorphous carbon.…”

“…The high-frequency shift in the 4100 cm −1 band position with T an occurs due to the relative amplification of the 4112 cm −1 component. These two components are well-known for diamonds with ACs [23][24][25][26][27][28][29][30][31][32][33].…”

“…This is believed to prevent the brown center formation in the extreme conditions of the Earth's upper mantle [26]. Nevertheless, the destruction of ACs by HPHT treatment is unexplained at this time [27]. The AC defect was suggested to relate to A-defects in diamonds, but no linear correlation between ACs and the aggregation state and total nitrogen content was found [24].…”

Структурные И Оптические Характеристики Синтетических Алмазов В Нано-, Микро- И Миллиметровом Масштабе

“…Полоса излучения образца 500 nm центрирована на 450 nm, образцов 1−2 и 100 µm -на 531 nm, алмазной пластины -на 498 nm. Как было показано, образование дефектов зависит от температуры отжига в процессе синтеза [28,29]. Время затухания люминесценции представлено на рис.…”