Contents lists available at ScienceDirect Ceramics International journal homepage: www.elsevier.com/locate/ceramint Short communication Effect of green body annealing on laser performance of YAG:Nd 3+ ceramics R.P. Yavetskiy a, ⁎ , S.V. Parkhomenko a , I.O. Vorona a , A.V. Tolmachev a , D.Yu. Kosyanov b , V.G. Kuryavyi c , V.Yu. Mayorov c , L. Gheorghe d , G. Croitoru d , M. Enculescu e a Institute for Single Crystals, NAS of Ukraine, 61072 Kharkiv, Ukraine b Far Eastern Federal University, 690950 Vladivostok, Russian Federation c Institute of Chemistry, Far-Eastern Branch, Russian Academy of Sciences, 690022 Vladivostok, Russian Federation d National Institute for Laser, Plasma and Radiation Physics, ECS Laboratory, P.O. Box MG-36, 077125 Magurele, Bucharest, Romania e National Institute of Materials Physics, P.O. Box MG-7, 077125 Magurele, Bucharest, Romania ARTICLE INFO Keywords: A. Sintering B. Porosity C. Optical properties E. Functional applications ABSTRACT Annealing temperature of green bodies has been shown to influence greatly the optical properties and laser characteristics of Y 3 Al 5 O 12 :Nd 3+ (1 at%) ceramics. Increase the annealing temperature above some critical one (800 °C) results in appearance of submicron pores due to Y 4 Al 2 O 9 phase formation accompanied by specific volume expansion. The energy changes associated with the chemical reaction can lead to the development of microstructures that possess lower sinterability. As a result, Y 3 Al 5 O 12 :Nd 3+ ceramics prepared from unannealed green bodies and those annealed at 600 and 800 °C possess higher optical transmittance and enhanced slope efficiency (63–67%) compared with that obtained using green bodies annealed at 1000 °C (41%). Further in- vestigations are necessary in order to explain this behavior. 1. Introduction Yttrium aluminum garnet ceramics doped with neodymium ions Y 3 Al 5 O 12 :Nd 3+ (YAG:Nd 3+ ), is prospective model object of the con- densed matter physics to establish correlation of densification on mi- crostructure evolution during sintering [1]. Besides, YAG:Nd 3+ is one of the most relevant material of modern quantum electronics and laser engineering [2]. Functional characteristics of optical ceramics depend largely on its densification routes and final microstructure. For ex- ample, laser efficiency of YAG:Nd 3+ ceramics is identical to single crystal counterpart at pore concentration below 10 -4 vol% [3–5]. Ef- fect of air annealing on functional characteristics of sintered YAG:Nd 3+ ceramics was studied in Ref. [6]. It was shown that annealing at 1450 °C for 8 h significantly improves slope efficiency of YAG:Nd 3+ ceramics due to reduction of color centers concentration. Influence of sintering heating rate on microstructure and lasing of YAG:Nd 3+ optical ceramics was investigated in [7]. Green body's mesostructure has an exceptional effect on properties of optical ceramics formed by reactive sintering of nano- and submicron powders [8–12]. At the same time densification is governed by grain growth, pore eliminations and coarsening processes [10,11]. Sintering studies of alumina powders revealed key indicators of successful “uni- form” powder densification, namely narrow pore size distribution, ab- sence of large pores (> 0.5 from mean particle size), low average pore size (≤ 1/5 from particle size) [13,14]. Influence of initial green body mesostructure on optical properties and functional characteristics of YAG:Nd 3+ ceramics has not been studied yet. This research aims to demonstrate that annealing of green bodies has a significant effect on physical properties as well as laser performance of neodymium-doped garnet ceramics. 2. Experimental 2.1. Obtaining of YAG:Nd 3+ ceramics YAG:Nd 3+ ceramics were produced by reactive sintering using high purity commercial oxides according to [15]. In brief, oxide powders were weighted according to YAG:Nd 3+ (1 at%) stoichiometry using TEOS as a sintering aid. Powder mixtures were ball milled, dried and sieved. The green bodies were cold isostatically pressed at 200 MPa and annealed at 600, 800 and 1000 °C for 4 h. Unannealed sample was used for the comparison purposes. The corresponding samples are denoted as “0”, “600”, “800” and “1000”. The sintering was performed using va- cuum furnace with tungsten heating elements at 1750 °C at 10 -3 Pa for 10 h. After sintering, the ceramics were annealed in air at 1300 °C for 15 h to recover oxygen vacancies. Finally, samples were mirror polished on both surfaces with different grade of the diamond slurries for testing optical transmittances and lasing behavior. https://doi.org/10.1016/j.ceramint.2017.11.192 Received 30 October 2017; Received in revised form 24 November 2017; Accepted 26 November 2017 ⁎ Correspondence to: Institute for Single Crystals, NAS of Ukraine, 60 Nauky Ave., 61072 Kharkiv, Ukraine. E-mail address: yavetskiy@isc.kharkov.ua (R.P. Yavetskiy). Ceramics International xxx (xxxx) xxx–xxx 0272-8842/ © 2017 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Please cite this article as: Yavetskiy, R.P., Ceramics International (2017), https://doi.org/10.1016/j.ceramint.2017.11.192