Fabrication of ferroelectric silicate KNbSi₂O₇ single crystal

Abstract

ABSi 2 O 7 is a new ferroelectric material group of which ferroelectricity has been discovered recently. In this study, we focused on potassium niobate silicate (KNbSi 2 O 7 ), which comprises displacement-type ferroelectric substance KNbO 3 and high-covalence substance SiO 2 in the structure. KNbSi 2 O 7 single crystals with a size of 10 © 10 © 1 mm 3 were fabricated by the process of glass crystallization, re-melting, and slow-cooling. The polarization-electric field (P-E) curve of the KNbSi 2 O 7 crystal was evaluated and KNbSi 2 O 7 evidently showed ferroelectricity in the direction of c axis. The value of the spontaneous polarization was estimated to 0.11¯C/cm 2 . The dielectric permittivity was approximately 15 for both a and c axes at 1 MHz, and this material was found to be a ferroelectric material with low dielectric permittivity.

Rippite, K2(Nb,Ti)2(Si4O12)O(O,F), a New K-Nb-Cyclosilicate from Chuktukon Carbonatite Massif, Chadobets Upland, Krasnoyarsk Territory, Russia

“…The discovery of rippite also highlights some problems in the synthesis and growth of high-quality crystals suitable for industrial purposes. It is known that synthetic analog of rippite is a good material for nonlinear optics [3][4][5][6][7][8][9][10][11][12][13][14]. Ideal and large single crystals of KNbSi 2 O 7 (near 1 cm) of high optical quality, which are valid for industrial purpose, are still rarity [14].…”

“…It is known that synthetic analog of rippite is a good material for nonlinear optics [3][4][5][6][7][8][9][10][11][12][13][14]. Ideal and large single crystals of KNbSi 2 O 7 (near 1 cm) of high optical quality, which are valid for industrial purpose, are still rarity [14]. The mineral association of rippite-containing calciocarbonatites may be a key in understanding of favorable conditions for synthesis of the perfect KNbSi 2 O 7 crystals (Ca-rich carbonate environment).…”

“…Single crystals, ceramics, glass-ceramics, and glass of KNbSi 2 O 7 and similar compositions in the systems SiO 2 (±GeO 2 )-Nb 2 O 5 -K 2 O have been fabricated [3][4][5][6][7][8][9][10][11][12]. The synthesis of glasses and glass-ceramics in the system SiO 2 -Nb 2 O 5 -K 2 O has shown that K 2 Nb 2 (Si 4 O 12 )O 2 may be appeared in the 510-735 • C temperature range in glass/melt [4,6,[8][9][10]13,14]. The KNbSi 2 O 7 phase has very high optical nonlinearity with its second harmonic generation (SHG) signal greater than that for α-quartz [14,15].…”

“…It is rather inert and chemically stable and is not dissolved in inorganic acids except HF. All studies on KNbSi 2 O 7 are mainly focused on its nonlinear optical property [3][4][5][6][7][8][9][10][11][12][13][14][15]. Single crystals, ceramics, glass-ceramics, and glass of KNbSi 2 O 7 and similar compositions in the systems SiO 2 (±GeO 2 )-Nb 2 O 5 -K 2 O have been fabricated [3][4][5][6][7][8][9][10][11][12].…”

“…The synthesis of glasses and glass-ceramics in the system SiO 2 -Nb 2 O 5 -K 2 O has shown that K 2 Nb 2 (Si 4 O 12 )O 2 may be appeared in the 510-735 • C temperature range in glass/melt [4,6,[8][9][10]13,14]. The KNbSi 2 O 7 phase has very high optical nonlinearity with its second harmonic generation (SHG) signal greater than that for α-quartz [14,15]. The study of ferroelectric-dielectric properties has shown that K 2 Nb 2 (Si 4 O 12 )O 2 is a ferroelectric material with low dielectric permittivity range {4,14].…”