Electronic structures and origin of intrinsic luminescence in Bi-containing oxide crystals BiPO sub(4), K sub(3)Bi sub(5)(PO sub(4)) sub(6), K sub(2)Bi(PO sub(4))(MoO sub(4)), K sub(2)Bi(PO sub(4))(WO sub(4)) and K sub(5)Bi(MoO sub(4)) sub( 4)

• Published in: Journal of alloys and compounds Vol. 614; pp. 420 - 435
• Main Authors: Hizhnyi, Yu A, Nedilko, S G, Chornii, V P, Slobodyanik, M S, Zatovsky, I V, Terebilenko, K V
• Format: Journal Article
• Language: English
• Published: 25.11.2014
• Subjects: Crystal structure; Crystals; Decay; Energy gaps (solid state); Excitation; Mathematical analysis; Origins; Texts
• ISSN: 0925-8388
• DOI: 10.1016/j.jallcom.2014.06.111

The origin of intrinsic photoluminescence (PL) in the set of Bi-containing phosphate, molybdate and tungstate crystals is analyzed in complex experimental and computational studies. The PL properties of polycrystalline powder samples of BiPO sub(4), K sub(3)Bi sub(5)(PO sub(4)) sub(6), K sub(2)Bi(PO sub(4))(MoO sub(4)), K sub(2)Bi(PO sub(4))(WO sub(4)) and K sub(5)Bi(MoO sub(4)) sub( 4) crystals synthesized by spontaneous crystallization method are studied under excitations in the VUV and UV region of photon energies (3.5-14 eV) at T = 8-300 K. The electronic band structures of the crystals are calculated by the Full-Potential Linear Augmented Plane Wave Method. The values of band gaps E sub(g) of studied compounds are estimated from diffuse reflectance and PL excitation spectra. Calculations indicate that all studied crystals except K sub(5)Bi(MoO sub(4)) sub( 4) are indirect-gap materials. It is found that the Bi 6s and Bi 6p states contribute respectively at the tops of the Valence bands and the bottoms of the Conduction bands of all studied compounds. Each studied compound reveals several (at least two) PL emission components which undergo complete quenching below room temperature. Under nitrogen laser excitation with [lambda] sub(ex) = 337.1 nm, all studied crystals reveal single-exponential decay of PL signal with decay constants [tau] in 3-35 mu s range. It is assumed that the high-energy PL components of BiPO sub(4), K sub(3)Bi sub(5)(PO sub(4)) sub(6) and K sub(2)Bi(PO sub(4))(MoO sub(4)) (peaking in the blue and violet regions) originate from super(3)P sub(1) arrow right super(1)S sub(0) radiative transitions in Bi super(3+) ions. The red PL components of K sub(2)Bi(PO sub(4))(MoO sub(4)) and K sub(5)Bi(MoO sub(4)) sub( 4) have the (ProQuest: Formulae and/or non-USASCII text omitted)-related origin. The red PL component of K sub(2)Bi(PO sub(4))(WO sub(4)) presumably originates from the molybdenum impurities which form (ProQuest: Formulae and/or non-USASCII text omitted) emission centers in the phosphate-tungstate host.