Structural and morphological characteristics of yttrium and lutetium orthoborates synthesized in thin layers of borate o
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We propose a new method of synthesis of crystalline yttrium and lutetium orthoborates in thin (2.5–20.0 lm thick) layers of molten borate oxide glasses. The method is based on interaction of nanosized lutetium and yttrium oxide powders with boron anhydride in the melt. X-ray diffractometry and electron microscopy investigations have revealed that in the case of lead-content glasses, the method shows a very strong orienting effect in the texture of the resulting orthoborate particles. This highly oriented texture results in good transparency of the obtained glass–ceramic films. Studies of the luminescence and scintillation spectra of the glass–ceramic composites show that they can be used as highly effective phosphors with a light yield comparable to that of single crystalline scintillators.
I. INTRODUCTION
Fabrication of optically active glass–ceramic materials is a fairly urgent problem. This is conditioned by feasible multifunctionality of such systems (phosphors, scintillators, optical transformers, active laser elements) and the essentially simple technology of their fabrication compared to single crystal growth technology. For years, the idea of producing optically active and transparent glass– ceramic materials has remained fairly popular, and numerous attempts have been made to realize it using a wide variety of crystalline and amorphous phases.1–6 In this work, lutetium and yttrium orthoborates were used as a crystalline part of glass–ceramic materials. Such orthoborates are well known as effective phosphors and scintillators.7–9 The most efficient and convenient method of fabricating such orthoborates is the reaction of rare earth oxide powders with boron anhydride B2O3 melt at elevated temperatures.10 This reaction is the basis of the processes realized in melts of boron oxides and alkaline metals, particularly in melts of tetra borax salts.11 This technique is used to obtain polycrystalline powders of individual rare earth orthborates with crystallite sizes from fractions to tens of micrometers as well as glasses with these compositions.12–14 We present the results of lutetium and yttrium orthoborate synthesis achieved by the reaction of lutetium and yttrium oxides with boron anhydride in the thin layers of the corresponding oxide glass melt. The specific reaction conditions determine the morphological and structural characteristics of the obtained glass–ceramic
materials that enable using them as effective scintillators for x-ray, particle, and gamma detectors. II. EXPERIMENTAL DETAILS
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2012.215
Na2O–18B2O3, K2O–2B2O3, 0.5PbO–B2O3, 0.69PbO– B2O3, 2.17PbO–0.44SiO2–B2O3 glasses were used as glass-forming media. NaNO3, K2B4O7d4H2O, H3BO3, PbO, and SiO2 compounds were used as glass components. Lutetium and yttrium oxides, activated by Ce31 (about 1 at.%), were obtained in the mode of combustion of the metal nitrite–citric acid complexes (1:2 mol relationship) by heating to 650 °C in an electric furnace. Only high purity age
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