Douglas A. Keszler

Borates for optical frequency conversion

Abstract Inorganic borate crystals find widespread application as non-linear optical materials in high-performance devices. During the past year, researchers have generated several new materials and achieved advances both in materials processing and in device engineering physics that will likely lead to a broader utility.

Red, green, and blue Eu2+ luminescence in solid-state borates: A structure-property relationship

The structures and luminescent properties of a series of Eu2+ doped Ba and Sr borates have been investigated. From this study, a simple structural relationship is established that distinguishes violet and blue emitting compounds from those that emit at longer wavelengths (> 500 nm). In this model, emphasis is placed on the coordination environments of the O atoms. Borates containing O atoms highly coordinated by heavy alkaline-earth metal atoms produce longer wavelength Eu2+ emission.

Structure and Eu2+ luminescence of dibarium magnesium orthoborate

Abstract The structure of the mixed alkaline-earth orthoborate Ba 2 Mg(BO 3 ) 2 , a buetschliite derivative, has been established with single-crystal X-ray diffraction methods. Crystal data: a = 5.343(2), c = 16.520(3) A, V = 408.4(2) A 3 , Z = 3, space group = R3m. A Eu 2+ -doped powder exhibits a luminescence peak at 608 nm and a Stokes shift of ~ 11,000 cm −1 .

CaAl2(BO3)2O: Crystal Structure

Abstract The structure of the aluminum borate CaAl 2 (BO 3 ) 2 O has been established by single-crystal X-ray diffraction methods. It crystallizes in the trigonal space group R 3 c ( h ) (Z = 6) with unit-cell parameters a = 4.810(6) A, c = 46.633(5) A, and V = 934(1) A 3 . The structure was determined from 274 unique reflections and refined to the final residuals R = 0.024 and wR = 0.032. It is characterized by an association of BO 3 triangles, CaO 6 octahedra, AlO 4 tetrahedra, and unique, two-coordinate O atoms. Structural comparisons are made to Na + β-alumina.

Alkali metal coactivators in SrS: Cu,F thin-film electroluminescent devices

A unique approach for obtaining bright and efficient saturated green phosphors for alternating-current thin-film electroluminescent (ACTFEL) device applications is presented. The approach involves color-shifting blue SrS:Cu,F ACTFEL phosphors into the green region of the spectrum via the incorporation of alkali metal ions into the SrS lattice. Alkali metals are incorporated into SrS:Cu,F phosphors by using LiF, NaF, KF, RbF, or CsF coactivators. The best result to date is obtained by using a KF coactivator and results in a saturated green brightness and efficiency of 52.7 cd/m2 and 0.973 lm/W (at a frequency of 60 Hz and an overvoltage of 40 V). In addition to providing a color shift, the alkali-metal fluorides improve the overall performance of the ACTFEL device by increasing the magnitude of the electric field and its uniformity across the phosphor through suppression of positive space charge.

Lanthanide doping in ZnS and SrS thin-film electroluminescent devices

The relative high field transport efficiency and short wavelength electroluminescence (EL) potential of the phosphors ZnS and SrS for alternating-current thin-film electroluminescent (ACTFEL) device flat-panel display applications are assessed via a comparison of the EL spectra of ZnS and SrS ACTFEL devices prepared in a very similar manner and doped with the same lanthanide luminescent impurities: Dy, Er, Ho, Tb, and Tm. For all of the lanthanide luminescent impurities studied, it is found that the the higher energy EL peaks are much more intense for SrS than for ZnS, even though the average phosphor field in SrS is smaller than in ZnS. These observations show SrS to be a superior high-field electron transport material compared to ZnS. All of the ZnS EL spectra show a dramatic cut off in their EL intensities at about 440–460 nm; this suggests that ZnS is not an appropriate phosphor for blue light emission since its electron distribution does not appear to be adequately heated to efficiently excite blue l...

The layered borate SrBe2(BO3)2

Abstract The compound SrBe 2 (BO 3 ) 2 crystallizes in the monoclinic space group P 2 1 / n in a cell of dimensions a = 9.247(1) A, b = 4.492(2) A, c = 11.561(1) A, and β = 112.17(1)° with Z = 4. Least-squares refinement affords the final residuals R = 0.034 and R w = 0.045. The structure consists of layers of composition [Be 2 (BO 3 ) 2 ] 2− that are interleaved by Sr atoms. Each layer contains two crystallographically inequivalent Be and B atoms; the Be atoms occupy distorted O tetrahedra while the B atoms occupy distorted triangular planar environments. Two Be atoms of one type share two O atoms to form a dimer of edge-shared tetrahedra. The Sr atom occupies a distorted monocapped 8-coordinate site.

The pentaborate Ba2LiB5O10

The structure of the compound Ba2LiB5O10 has been established by single-crystal X-ray methods. It crystallizes in the monoclinic space group P21/m in a cell of dimensions a = 4.414(1), b = 14.576(2), c = 6.697(2) A, and β = 104.26(2)° with Z = 2. Refinement from 2373 independent reflections affords the final residuals R = 0.021 and RW = 0.042. The structure exhibits a unique one-dimensional polyborate anion built from two crystallographically independent BO3 groups and a distinct BO4 group that share vertices. The polyanions are bridged by a Li atom occupying a distorted tetrahedral site and a Ba atom occupying an irregular eightfold coordinate site.

Stoichiometric, trigonal huntite borate CeSc3(BO3)4

Abstract Crystals of stoichiometric CeSc 3 (BO 3 ) 4 (CSB) have been grown from a high-temperature solution by employing an LiBO 2 /LiF flux. The structure has been determined from single-crystal X-ray diffraction measurements; it crystallizes with three formula units in a trigonal cell of dimensions a =9.796(1) and c =7.960(2) A. The nonlinear optical response and luminescence data for CSB are presented, and an energy-level scheme for the Nd-doped compound is derived.

Structure of distrontium scandium heptafluoride and chromium(III) luminescence

The crystal structure of the compound Sr2ScF7 has been established by single-crystal X-ray diffraction methods to determine the local F arrangements about the Sr and Sc atoms. The monoclinic three-dimensional framework contains 7-coordinate Sc atoms and [9 + 1]- and 9-coordinate Sr atoms. The luminescence spectrum of Cr3+:Sr2ScF7 exhibits a broad emission band extending from 740 nm to 940 nm with a maximum at 844 nm.