The growth features of trigonal La3Ga5SiO14 and Nd3Ga5SiO14 crystals and their solid solutions from the melt by Czochralski technique are studied. Optimal conditions are found and oriented (La1−xNdx)3 Ga5SiO14 single crystals are grown with 28 mm in diameter and 280 g by weight, of optical quality perfect to carry out excitation experiments on Nd3+ ion stimulated emission as well as investigations of acoustooptic and electromechanical properties of La3Ga5SiO14 crystals. Structural peculiarties and desorderness of La1−xNdx)3Ga5SiO14 crystals are considered. Crystal optics of La3Ga5SiO14 – linear dichroism and dispersion of refractive indexes (by a modified prism method), optical activity, and other optical characteristics are investigated. A comparison is made of some optical properties of La3Ga5SiO14 crystals and crystalline SiO2.

Structure peculiarities and disorderness of trigonal Ca3Ga2Ge4O14 and Sr3Ga2Ge4O14 crystals are considered. Absorption and luminescence characteristics and stimulated emission parameters of Nd3+ ions in said compounds are investigated. The luminescence intensity parameters of the activator are analyzed and the cross‐sections of its induced transitions at the wavelengths of the two lasing 4F3/2 → 4I11/2 and 4F3/2 → 4I13/2 channels are determined. All registered induced transitions are identified. The electromechanical properties of Ca3Ga2Ge4O14 and Sr3Ga2Ge4O14 crystals, including elastic, dielectric, and piezoelectric modulus and constants are studied.

Absorption, luminescence characteristics, and stimulated emission parameters of Nd3+ ions in the wide temperature region of a full concentration series of (La1 -,Nd,),Ga,SiO,, single crystals are studied. Luminescence intensity characteristics are analyzed and transition cross-section a t the laser wavelengths of two 4F3jz 4 *I11p and 'F3p -4113jz generation channels of activator are determined. Registered induced transitions are identified. Electromechanical characteristics of La,Ga,SiO,,, specifically, elastic, dielectric, and piezoelectric modules and constants are investigated. A comparison of the properties between Ls,Ga,SiO,, crystals and crystalline SiO, is carried out. kI3yqeHbI a 6 C O p 6~M O H H O -n~M H H e C r I e H T H b I e XapaKTePHCTkiKI4ki IIapaMeTpbI CTMMyJIPIpO-BaHHOrO H3JlyseHkiH HOHOB Nd3+ B UIHPOKOM HHTepBane TeMnepaTyp IIOJIHOfi IFOHUeH-TpauMoHHOZi CepMH MOHORpHCTanJIOB (Lal-,Nd,),Ga,SiO,,. rIpOaHaJIM3MpOBaHbI MH-TeHcmHocTHbie xapaEcTepmcTmm moMmecueHIIm M onpenenem1 nonepewme cezIeHan nepexonoB Ha BonHax reaepaum ~B Y X naaepabix 4F3p + 4111p M 4F3p + 4113/2 KaHanoB MccnenonaHbI 3nempo-Mexamsecmie xapaKTepmmim La,Ga,SiO,,, B YacTHoCm, ynpyrkie, ~H~J I~K T~L Z = I~C K H~ M I I~~~O~J I~K T~M~~C I C M~ MOJQVIM PI nocTomume. nposeneiro cpaBHeHne C B O~~C T B La,Ga,SiO,, M KpMcTanmi~ecKoro SiO,.ZiKTXBaTOpa. MAeHTM@M4HPOBaHbI 3aperHCTpMpOBaHHbIe MHjQW4pOBaHHble IlepeXoAhI.in the whole interval of concentration x ( a t 4F3j2 -4111jz channel). Moreover, laser action with low threshold can be excited by the emission of convenient pumping sources as gas flash tubes. Preliminary information on La,Ga,SiO,, electromechanical characteristics can be taken from [4]. The possibility of growing large (Lal-,Nd,),Ga,SO, single crystals with high optical perfection, and the combination of satisfactory laser and piezoelectric properties make these crystals perspective materials for application in quantum electronics, piezotechniques, and acoustics, and also open interesting perspectives for putting experiments, e.g. on generation and study of the physics of very high frequency phonons of the THz range and investigations of electron-phonon interaction by piezo-and photoacoustic methods. The aim of the present work was the detailed study of absorption and luminescenceproperties with the analysis of intensity characteristics, and stimulated emission (SE) parameters of (Lal-,Ndz),Ga,SiO, crystals as well as measurements of their basic electromechanical constants such as elastic, dielectric, and piezoelectric constants. l) Leninskii prospekt 59, 117333 MOSCOW, USSR. 2) Part I see phys. stat. sol. (a) 80, 387 (1983). 39 *

I. M. Sil'vestrova and N. N. Sobolev The P. N. Lebedev Physical Institute, Academy of Sciences of the U.S.S.R., Moscow, U.S.S.R. The Mandel'shtam-Brillouin spectra of single crystals of Zr02-Yz03 and Hf02-Yz03 solid solutions have been measured and the results explained qualitatively. Using the methods of Mandel'shtam-Brillouin spectra and ultrasound propagation the elastic and photoelastic constants of single crystals of ZrOz-YzO, and HfOt-Y203 solid solutions have been found and their dependence on the composition obtained. The elastic and photoelastic properties of single crystals of these solid solutions are discussed.

The acoustic and elastic characteristics of zinc tungstate crystals are determined. It is found that ZnWO4 has a considerable elastic anisotropy and large mechanical impedance.